In the long-distant past, our ancestors discovered that processing some natural products created glues. The raw materials either came from boiling animal bones, hide, and other offal, or from natural exudates of plants, and these came to be used as the binder for paints. Being ancient in origin, different combinations of binder, pigment, and other substances developed, and those have left a confusion of terms, including glue tempera, and distemper. These represent a spectrum of paints, ranging from those using only glue and pigment, to others also incorporating substantial amounts of powdered chalk or lime to increase their opacity, and related to whitewash.

Glue tempera was used in antiquity, and outside Europe remains in widespread use. It has several disadvantages for the painter, including:

• ‘Drying light’; as the paint dries, so it undergoes marked colour change, reducing the intensity of chroma.
• Mechanical fragility of the paint layer, which is particularly susceptible to abrasion and/or cracking.
• Solution on re-wetting, so that glue tempera can easily be reworked like watercolour, but is unsuitable for exposure to water or damp. Hardening of the glue binder isn’t the result of a stable polymerisation as with oil paints, and can readily be reversed.
• Relatively poor protection of light-sensitive pigments, resulting in some fading over time.

Taken together these mean that what we see in glue tempera paintings today is often quite different from how they looked at the time they were painted.

In the early Renaissance, some artists used glue tempera extensively and with great success, although surviving works haven’t aged as well as those painted using egg tempera or oils.

Dieric Bouts’ The Entombment from about 1450 was painted using glue tempera on linen. As it’s now well over half a millennium old its colours have faded, but it remains worth seeking out when you next visit The National Gallery in London.

In the south of Europe, Andrea Mantegna was one of its great exponents, as shown in his marvellous glue tempera and gold painting of A Sibyl and a Prophet from about 1495. Because this is monochrome and uses gold as the pigment, this has neither changed colour nor faded.

Some artists, such as Joris Hoefnagel, continued to use these ancient techniques, as shown in this painting of Diana and Actaeon from 1597. This is finely executed in glue tempera and gold on vellum, and its colours have survived well.

With the widespread adoption of oil paint, glue tempera almost disappeared until it was revived at the end of the eighteenth century by William Blake.

Blake painted a series of major works in what he termed tempera, using glue as their binder. This Adoration of the Kings from 1799 shows the dulling of colour and fine cracking from his use of stretched canvas as its support.

Some of Blake’s glue tempera paintings have survived in better condition: The Christ Child Asleep on the Cross, or Our Lady Adoring the Infant Jesus Asleep on the Cross from 1799-1800 has fared better, retaining more of its original colour.

Paintings such as Blake’s Virgin and Child in Egypt from 1810 show the fine modelling he was able to achieve in its figures. Overall, though, the condition of his glue tempera paintings isn’t good. It has been suggested that some of their variation is attributable to different sources of glue, clearly of major importance. For a long time, glues provided for this and similar purposes in painting have been referred to as rabbit skin glue, but in reality the great majority have been derived from a wide range of animal products, often in uncontrolled conditions.

After Blake, the medium fell back into obscurity until later in the nineteenth century, when it was revived by movements attempting to return to techniques of the past, most prominently the Nabis in France.

Pierre Bonnard used glue tempera early in his career, when painting this exquisite three-panelled Japoniste screen of The Stork and Four Frogs in about 1889, as the Nabis were forming. Using more modern pigments, Bonnard has achieved high chroma, comparable to anything in oils, and quite unlike traditional glue tempera.

Odilon Redon experimented with glue tempera in his painting of Buddha from 1904.

Édouard Vuillard used glue tempera in many of his paintings both during his Nabi period and later, for example in this view Under the Trees of the Red House from about 1905.

Vuillard’s At The Pavillons in Cricqueboeuf. In Front of the House, from 1911, shows how effective the medium can be.

Vuillard continued to use glue tempera in his late realist paintings, such as Morning Concert, Place Vintimille from 1937-38, showing a trio of friends playing for the artist in his Paris apartment.

Glue tempera remains in use today by a very few artists, who at least have a wider range of lightfast pigments to choose from, and more consistent formulations of glue to act as binder.

In the last few months I have had reports from several whose Macs have experienced a “SEP Panic” rather than a regular kernel panic. Although the immediate effects are the same, and my previous advice on how to deal with a kernel panic still applies, this article looks in more detail at what should be exceedingly rare events.

Essentials

If your Mac restarts or shuts down spontaneously, or ‘freezes’ for you to force it to shut down, chances are that was a kernel panic. When it starts up again, look out for the dialog inviting you to send a report to Apple. Expand that so you can see the panic log, copy and paste that into a text document, and save it. That’s the only record you have of that report, and that provides valuable clues as to what went wrong and how you might go about fixing it.

Apple will not contact you in response to sending the panic log. If you want advice or assistance about your Mac, contact Apple Support, and ensure you have your copy of the panic log ready, as they’ll need to see it.

Secure enclave

No matter how secure you try to make an operating system, if its most precious secrets are being processed by the main CPU cores, an attacker will find a way to access them. The proven solution to this is to build in a separate part of the chip with its own processor, and isolate that from everything else – a secure enclave, with its own secure enclave processor, SEP, as patented by Apple 13 years ago.

Two Mac architectures have secure enclaves and SEPs: Intel Macs with T2 (and T1) chips, where the SEP is in the T2/T1, and Apple silicon Macs, where the SEP is an integral part of the chip. These handle several different security features, including biometrics in Touch ID, management of secure encryption keys including those for FileVault, and performing encryption and decryption for the internal SSD.

The SEP runs its own operating system, sepOS, thought to be a derivative of L4, and communicates with the rest of the chip using mailboxes. When the CPU needs something from the SEP, it posts a message in the SEP mailbox, then retrieves the response when the SEP has processed that request.

What could possibly go wrong?

Like all processors, the SEP can hit problems that it can only manage by a reset, and those will result in it panicking, which in turn provokes the kernel running on the CPU to panic. Those problems can result from anything from a hardware fault to a bug in sepOS.

The SEP in a T2 chip is also known to be vulnerable to some exploits including blackbird, which can be used to ‘jailbreak’ a device using checkra1n or with malicious intent.

Reading the SEP panic log

When a kernel panic is the result of a SEP panic, the panic log is different from normal, and contains considerable detail about the SEP and what went wrong with it. As usual, though, much of that information is cryptic to say the least.

The first line in the panic log confirms that the panic originated in the SEP
panic(cpu 1 caller 0xfffffe001f55e344): SEP Panic: […]

You’re then given the version of sepOS
Root task vers: AppleSEPOS-2772.140.4

Unfortunately, further down it disclaims knowledge of that
Firmware type: UNKNOWN SEPOS

The status of the SEP’s mailboxes are given
Mailbox status:
IDLE_STATUS: 0x00000008
INBOX0_CTRL: 0x00105601
OUTBOX0_CTRL: 0x00023301
and
Mailbox entries:
Unavailable
Mailbox queue pointers: […]

This is confirmed as a panic
Debugger message: panic

The version of macOS is given by build number, with details of the kernel running on the CPU
OS version: 24G90
Kernel version: Darwin Kernel Version 24.6.0: Mon Jul 14 11:30:29 PDT 2025; root:xnu-11417.140.69~1/RELEASE_ARM64_T6000
For a T2 chip, the kernel version given should be for a T8010
root:xnu-11417.140.69~1/RELEASE_ARM64_T8010

Apple silicon Macs should then confirm their iBoot versions, first the LLB (Stage 1) then iBoot Stage 2, and whether Secure Boot was used
iBoot version: iBoot-11881.140.96
iBoot Stage 2 version: iBoot-11881.140.96
secure boot?: YES

T2 SEPs don’t normally give an iBoot Stage 2 version, but provide information about the Intel (x86) host
iBoot Stage 2 version:
secure boot?: YES
roots installed: 0
x86 EFI Boot State: 0xe
x86 System State: 0x0
x86 Power State: 0x0
x86 Shutdown Cause: 0x5
x86 Previous Power Transitions: 0x20002000200
PCIeUp link state: 0x94721611

Information is provided about the task running on the CPU, which should normally be the kernel
Panicked task 0xfffffe1fb0037248: 0 pages, 654 threads: pid 0: kernel_task

Towards the end of the panic log are details about kernel extensions. In SEP panics, that includes the SEP Manager
Kernel Extensions in backtrace:
com.apple.driver.AppleSEPManager(1.0.1)[UUID]@0xfffffe001f5366e0->0xfffffe001f566a63
and
last started kext at 242997189818: com.apple.iokit.SCSITaskUserClient 500.120.2 (addr 0xfffffe001ce0f6a0, size 2206)
loaded kexts:
In the list of loaded kernel extensions that follows, ensure there are no third-party entries, unless your Mac is expected to load them.

Actions

Although you should take a SEP panic seriously, there’s no need to panic yourself. This doesn’t mean that your Mac’s SEP has died, has been attacked by malware, or has released all the secrets it protects. A single panic in isolation could well just be chance, and not indicative of anything serious.

Provided that your Mac starts up correctly and then runs normally, your only essential task is to ensure that you capture and keep a copy of the panic log. If you wish, you can run hardware Diagnostics, but I doubt whether that performs any specific test intended to detect problems in the SEP. If you have potentially problematic peripherals, or any third-party kernel extensions, then you should take the hint and try to eliminate them.

If your Mac suffers any further kernel panics, capture their panic logs, and contact Apple Support with those to hand. Alternatively, book your Mac into an Apple store or authorised service provider for them to check it out for you.

Summary

• SEP panics are exceedingly rare, but are readily identified from the first line of the panic log.
• Ensure you copy and save a copy of the panic log.
• Much of the panic log will appear meaningless, but there is some information about version numbers and kernel extensions that may be helpful.
• Follow the normal recommendations, considering hardware diagnostics, and updating/removing potentially troublesome peripherals and third-party kernel extensions.
• If there are any further panics, capture those and obtain support from Apple.

References

How to deal with a kernel panic (this blog)
Apple, Platform Security Guide
Manu Gulati, Michael J Smith and Shu-Yi Yu, US Patent 8,832,465 B2, Security enclave processor for a system on a chip, filed 25 September 2012, granted 9 September 2014.
Tarjei Mandt, Mathew Soling and David Wang (2016), Demystifying the Secure Enclave Processor, Black Hat USA 16 (PDF)
Blackbird SEP exploit, Apple Wiki.

I’m very grateful to Joe, Marc and another for sharing their SEP panic logs.

After hearing Francesca’s story in the Second Circle of Hell, for those guilty of the sin of lust, Dante weeps for her and faints. When he comes to, he realises that he has already descended to the Third Circle, where it’s pouring with rain, with snow and huge hailstones falling down in sheets. This soaks the ground, turning it into stinking mud.

He sees Cerberus, the fearsome three-headed canine monster that guards this circle, also soaked by the unceasing rain.

Agostino Carracci’s portrait of Pluto from 1592 shows Cerberus alongside his master, and the god holding the key to his kingdom.

Its heads bare their fangs at Dante, but his guide Virgil scoops up three handfuls of mud and throws them into the mouths of Cerberus to assuage its hunger.

Dante and Virgil walk on the flat plain among the prostrate forms of the gluttons. One of them sits up and accosts Dante, reminding him that they knew one another. He is Ciacco (a nickname, literally ‘Hoggio’), who tells Dante of his suffering there, and the names of five other Florentines of noble rank who are to be found in the lower circles of Hell.

Ciacco then falls flat on his face in the stinking mud to await the Final Judgement.

As Virgil leads Dante down to the next circle, they talk of what will happen when the Apocalypse comes, until they reach the dreaded figure of Plutus.

Cerberus is a good example of the redeployment of pre-Christian mythology into Christian beliefs: it was originally the guardian of the Underworld, as depicted by Carracci, and prevented those within from escaping back to the earthly world. It even features in the twelve labours of Hercules, in which he captured Cerberus. With Virgil’s explicit involvement, Dante here incorporates it into his Christian concepts of the afterlife.

The artists

Giuseppe Arcimboldo (1527–1593) was a highly original and individualistic Italian painter now best known for his portraits consisting of assemblies of fruit, vegetables and other objects to form human images. He also painted more conventional works which are largely forgotten today, and was court painter to the Habsburgs in Vienna and Prague. You can see some of his portraits in this article.

William Blake (1757–1827) was a British visionary painter and illustrator whose last and incomplete work was an illustrated edition of the Divine Comedy for the painter John Linnell. Most of his works shown in this series were created for that, although he did draw and paint scenes during his earlier career. I have a major series on his work here.

Agostino Carracci (1557-1602) was one of the Carracci trio, the others being his brother Annibale and cousin Ludovico, who were largely responsible for the reputation of the School of Bologna in Italy. After working as an engraver, he painted a series of major frescos showing the story of Jason and Medea, and the early history of Rome.

Gustave Doré (1832–1883) was the leading French illustrator of the nineteenth century, whose paintings are still relatively unknown. Early in his career, he produced a complete set of seventy illustrations for translations of the Inferno, first published in 1857 and still in use. These were followed in 1867 by more illustrations for Purgatorio and Paradiso. This article looks at his paintings.

John Flaxman (1755–1826) was a British sculptor and draughtsman who occasionally painted. When he was in Rome between 1787-91, he produced drawings for book illustrations, including a set of 111 for an edition of The Divine Comedy. In 1810, he was appointed the Professor of Sculpture to the Royal Academy in London, and in 1817 made drawings to illustrate Hesiod, which were engraved by William Blake.

Joseph Anton Koch (1768-1839) was an Austrian landscape painter, who worked mainly in Neoclassical style. During his second stay in Rome, he was commissioned to paint frescos in the Villa Massimi on the walls of the Dante Room there, which remain one of the most florid visual accounts of Dante’s Inferno. He completed those between 1824-29.

Philippe Semeria is a young contemporary artist who is an enthusiast for comics and is an aspiring illustrator.

Jan van der Straet, also commonly known by his Italianised name of Giovanni Stradano (1523-1605), was a painter who started his career in Bruges and Antwerp in Belgium, but moved to Florence in 1550, where he worked for the remainder of his life. Mannerist in style, he worked with printmakers in Antwerp to produce collections of prints, including an extensive set for The Divine Comedy.

References

Wikipedia
Danteworlds

Robin Kirkpatrick (trans) (2012) Dante, The Divine Comedy, Inferno, Purgatorio, Paradiso, Penguin Classics. ISBN 978 0 141 19749 4.
Richard Lansing (ed) (2000) The Dante Encyclopedia, Routledge. ISBN 978 0 415 87611 7.
Guy P Raffa (2009) The Complete Danteworlds, A Reader’s Guide to the Divine Comedy, Chicago UP. ISBN 978 0 2267 0270 4.
Prue Shaw (2014) Reading Dante, From Here to Eternity, Liveright. ISBN 978 1 63149 006 4.

I hope that you enjoyed Saturday’s Mac Riddles, episode 322. Here are my solutions to them.

1: It’s about evolution, and open source for 25 years.

2: If the kernel isn’t Unix, this is it.

3: Mud puddles in Pittsburgh misheard as the basis for 2.

The common factor

I look forward to your putting alternative cases.

As promised, this new version of my Spotlight indexing and search utility SpotTest extends its reach beyond the user’s Home folder, and can now test and search any regular volume that’s connected to your Mac and mounted in /Volumes.

By default, its searches remain restricted to the user’s Home folder, where SpotTest’s folder of crafted test files is installed. That applies whether you opt to use the search using its NSMetadataQuery tool, or the much faster option of the mdfind tool instead. If you want to search another mounted volume, click on the button for the app to check which volumes are available, then select one from its new Scope menu items. Volumes listed there exclude Time Machine backups and any hidden volumes whose names start with a dot, which will in any case be excluded from Spotlight indexing as they’re hidden.

This new version also fixes a weird bug that you’re unlikely to encounter in the previous version, but in rare circumstances could be infuriating. When searching using the NSMetadataQuery tool, if you had two windows open both with results from that tool, both would be updated with the same search results, and the time taken in them could rise to the absurd. This occurred because both windows were being updated with the data returned from the most recent search, as the NSMetadataQuery is shared in the app’s MainActor. After some fraught debugging, windows in this version ignore any search result updates initiated by other windows. I hope!

Volumes set in the Scope menu only affect search scope. Test folders are created in and removed from the user’s Home folder, and mdimporters are checked there as well. If you want to investigate indexing and search performance on other volumes, then you should manually create your own test folders as necessary. One quick and simple approach is to create a standard test folder in the Home folder, and copy that onto the volume(s) you want to test. A little later this week I’ll illustrate this in an article explaining how to get the best out of SpotTest and how it can help diagnose Spotlight problems.

I have taken the opportunity to improve SpotTest’s reporting of errors, such as trying to remove a test folder that doesn’t exist. I have also thoroughly revised the Help book, and added a page about search scopes.

SpotTest version 1.1 for macOS 14.6 and later, including Tahoe, is now available from here: spottest11
from Downloads above, and from its Product Page.

Enjoy!

Once the ripe grain had been cut, the crop had to be gathered into sheaves, then those were assembled into stooks for transport by cart to await threshing, mechanical separation of the precious grain from straw. The latter was an important building material, and was used as thatch for the roof of most country buildings across Europe.

Anna Ancher, wife of Danish painter Michael Ancher, caught this procession of Harvesters on their way to their work in 1905, near her home in Skagen on the north tip of Jylland (Jutland). The leader carries his scythe high as they pass through a field of ripe wheat.

Léon Augustin Lhermitte’s famous Harvesters’ Pay from 1882 shows four harvesters bearing their heavy-duty scythes, at the end of the day. They are awaiting payment by the farmer’s factor, who holds a bag of coins for the purpose. In the right foreground are two tied sheaves of cut wheat, with a lightweight sickle resting on them.

Adrian Stokes had further to travel for this golden view of Harvest Time in Transylvania (c 1909), one of many paintings that he and his wife made of their protracted visits to Eastern Europe.

By tradition on Norwegian farms, cut cereal wasn’t left to dry in low stooks, as in most of Europe and America, but built onto poles. In a series of paintings and prints, Nikolai Astrup developed these Corn Stooks (1920) into ghostly armies standing on parade in the fields, the rugged hills behind enhancing their strangeness.

John Linnell’s Harvest Home, Sunset: The Last Load (1853) shows the final wagonload of cut grain leaving the fields at dusk, as the harvest is completed.

Félix Vallotton’s The Sheaves from 1915 is one of his moving and symbolic images of the Great War. It’s late summer in 1914, harvest time, and the ripe corn is being cut and stacked in sheaves. But where are all those farmworkers, whose rakes rest against the sheaves, and whose lunch-basket sits on the ground ready to be eaten? Where is the wagon collecting the harvest, and why is the white gate in the distance closed?

In PS Krøyer’s Threshing in the Abruzzi from 1890, teams of oxen are trampling the crop to thresh it.

Jean-Léon Gérôme’s The Grain Threshers, Egypt (1859) also shows this as one of the more traditional employments for animals, here drawing a threshing sledge.

By the end of the nineteenth century, animals were being used as a source of power, as shown in Albert Rigolot’s painting of The Threshing Machine, Loiret from 1893. One of the early uses for steam engines was to power similar machines before they were made mobile under their own power, as traction engines.

As we near the end of Tahoe’s incubation period, and Apple’s engineers code its last fixes and tweaks ready for its launch in just a few weeks, I’d like to reflect on what macOS 26 has to offer beyond its marketing headlines.

While there are several worthwhile new features such as the Phone app, Magnifier, and live translation, there’s nothing to compare with the fundamental changes in recent versions of macOS that brought the SSV, Shortcuts, System Settings and Apple Intelligence. Instead Tahoe is overwhelmingly about its human interface.

Every new design of the Mac’s operating systems that I can recall has elicited outcry from many. Understandably, the majority almost invariably want constancy, the same Finder and app icons that we’ve become so familiar with. It’s only human. It’s also a sure route to what others will condemn as stale, as it hasn’t been refreshed for so many years.

Personally, I don’t like to see a design on my Mac. If I notice it, then it’s a distraction. I’d much prefer to have an interface as clean as the whistles of the late Classic Mac OS period: lean, purposeful and lacking in visual trickery or frippery. But I accept that, without all the adornments and animations, many today would wonder why their Mac needed a GPU. I confess that I was never a fan of the original Aqua interface either. Given that its declared goal was to “incorporate colour, depth, translucence, and complex textures into a visually appealing interface”, I wonder whether much the same could be said of Tahoe.

Perhaps the most striking feature of this redesign is its lack of contrast between elements and tools in window controls and their contents, whether its appearance is set to light or dark mode, or one of its new in-between variants. You can see this clearly in most screenshots of Tahoe, such as those posted by Apple, and as far as I can see it hasn’t improved during beta-testing. This is also universal, and isn’t confined to apps using the more novel SwiftUI, although I have to keep pinching my thigh to remind myself that SwiftUI is now six years old, only two years younger than APFS. The contrast in stability and maturity between the two couldn’t be greater.

You can of course ‘improve’ contrast by enabling Reduce Transparency in Accessibility settings, but in doing so you lose most if not all of Tahoe’s Liquid Glass effects, as they depend on the transparency you’ve just turned off.

Transparency is a good example of design being given priority over readability or content. Because the appearance of the upper layer containing controls or content depends on what is underneath, it’s down to chance whether the greyed text you’re struggling to read happens to be over a background that further reduces its contrast. In the worst case, you could find yourself having to move a window so you can read part of it clearly, not a sign of a good human interface.

My other major concern with Tahoe’s new look is that it seems not to recognise the differences between Macs, iPads and iPhones, in terms of displays, input controls, and apps. Rather than sameness, I’d much rather have consistency that recognises the difference between manipulating Xcode’s compound windows containing dense structured text on a 27-inch display, and checking a family photo filling the 6.1-inch display of an iPhone.

One of my favourite controls in macOS is the Combo Box, a versatile and elegant hybrid of the popup/dropdown/pulldown menu/button and a text entry box. I can’t recall seeing one used in iOS, as it would be clumsy and inappropriate. It’s well supported for macOS in AppKit but hasn’t yet been implemented in SwiftUI. If controls are going to be common across all Apple’s operating systems, then macOS is about to lose one of its best.

It seemed only appropriate that, in the weeks before Apple releases OS 26 across Macs and devices, Tim Cook should go to the White House to pay its corporate tribute in a block of materialised Liquid Glass mounted on pure bling. But the image that I keep thinking of in fear, is that of Elon Musk demonstrating the resilience of his Cybertruck’s window by throwing a metal ball at it, in November 2019. I just hope Tahoe’s Liquid Glass doesn’t go the same way.

This is the time of year when, in the Northern Hemisphere, the grain harvest is in full swing, when the fields of cereal crops have ripened gold in the summer sun and are ready to be cut. This weekend I celebrate the climax of the farming year with some of the finest paintings of harvest in European art. Today I concentrate on cutting using a reaping hook or scythe, and tomorrow I look at the formation of sheaves and stocks, and threshing to separate the grain.

In the centuries before mechanical harvesting, cutting the crop was hard work and labour-intensive. It took about 4 worker-days to cut an acre of grain using a sickle or hook, while using a scythe typically took only 2 sweated worker-days per acre. Scythes appear to have been used almost exclusively by men, while sickles and hooks were used by both men and women.

Pieter Brueghel the Elder’s Harvesters from 1565 shows the whole village turned out to cut, process and transport the crop. This is a visual encyclopaedia of each of the steps involved in the grain harvest, as shown in the details below.

These men are cutting a crop of wheat close to the base of the stem using scythes, leaving short stubble. This ensures the best yield of straw as well as grain.

Behind these workers eating bread baked from flour ground from cereal grown in the same fields, cut cereal is tied first into sheaves before they are gathered into stooks.

In about 1833, when Samuel Palmer painted his wonderful Harvest Moon near Shoreham in Kent, harvesting usually went on well into the night. These are mostly women wielding sickles or reaping hooks to cut a small field of wheat. The cut stalks are then formed into stooks and piled onto an oxcart for transport to nearby farm buildings.

Palmer’s mentor John Linnell painted The Harvest Cradle twenty-five years later, in 1859. The harvesters have their backs to the viewer, but appear to be using scythes to cut this wheat crop. Bundles of cut grain are tied as sheaves, then assembled into stooks in the foreground.

He painted Wheat for the dealer Thomas Agnew in about 1860, and it became one of Linnell’s more successful works. It was shown at the Royal Academy shortly after completion, then at the Exposition Universelle in Paris in 1867.

Jean-François Millet’s Ceres (The Summer) from about 1864-65 is unusual in showing the goddess holding a sickle with a serrated edge, surrounded by sheaves of wheat. On her left she holds a shallow winnow used to separate the lighter chaff from the heavier grain, after threshing.

During the nineteenth century some attached cradles to the blade, to make sheaving easier. This is shown in Laurits Andersen Ring’s painting of Harvest. The crop being cut here may well be rye rather than wheat. The artist got his brother to model for this “monument to the Danish peasant” during the summer of 1885, while working on his farm near Fakse, on Sjælland (Zealand), Denmark.

Volodymyr Orlovsky’s Harvest in Ukraine from 1880 shows wheat being cut on the steppe, with the worker in the foreground carrying a scythe, but those cutting in the middle distance bent over as if using hooks instead.

The young woman in Mykola Pymonenko’s portrait of a Reaper from 1889 has been cutting what could be rye or wheat using a heavier bagging hook, although she isn’t using the hooked stick normally required for the technique, so could be using it as a regular reaping hook. The woman behind her demonstrates that these harvesters are cutting low to keep a good length of straw on the harvested crop.

Here are this weekend’s Mac riddles to entertain you through family time, shopping and recreation.

1: It’s about evolution, and open source for 25 years.

2: If the kernel isn’t Unix, this is it.

3: Mud puddles in Pittsburgh misheard as the basis for 2.

To help you cross-check your solutions, or confuse you further, there’s a common factor between them.

I’ll post my solutions first thing on Monday morning.

Please don’t post your solutions as comments here: it spoils it for others.

When Mac OS X 10.0 was released in March 2001, privileges, permissions and security adopted a conventional model based on BSD and Unix. Those sufficed for 15 years until the release of OS X 10.11 El Capitan in September 2015, when System Integrity Protection, SIP, was introduced. This article outlines its history over the last decade.

2015 Introduction

The first public account of SIP was presented by Pierre-Olivier Martel at WWDC 2015 in June, and documented in Apple’s System Integrity Protection Guide that September, which hasn’t been revised since. These changes were justified as adding a further layer of security protection to prevent attackers from gaining full control by escalating privileges to root.

Three types of protection were promised:

• file system protections, so that system files could only be modified by processes signed by Apple;
• prevention of runtime attachment, code injection, or modification of system binaries, with modifications only permitted by Apple’s installers and updaters;
• kernel extensions (kexts) had to be signed using special certificates granted by Apple.

Each Mac’s SIP configuration was stored in NVRAM, and controlled by the csrutil command used in Recovery mode.

When released, the csrutil command provided some degree of separate control over six groups of features: file system protections, debugging protection, DTrace protection, kext signing requirement, NVRAM and ‘Apple internal’ protection. One immediate beneficial side-effect was that SIP prevented permissions being changed for system files, and that made the practice of repairing permissions on them unnecessary, allowing removal of support for that procedure from Disk Utility.

2015 Conflicts

Press reviews of the SIP feature were divided, with some claiming it was a sign that OS X was being closed down and moved to the iOS security model, while others considered that few users would notice much difference.

Problems resulting from SIP were reported soon after El Capitan’s release. For example, some older Mac models intentionally prevented their use with Apple USB SuperDrives. One workaround to address that had been to modify one of the files now protected by SIP, which consequently required the user to disable SIP to make that change.

As kernel extensions hadn’t previously been required to be signed at all, other early casualties were all older unsigned kexts, making some apps unusable unless a new version was provided with a correctly signed kext.

2016 Error

Late in 2016, it became clear that Apple had shipped a substantial batch of new MacBook Pro systems with SIP disabled. At that time, System Information was unable to report SIP status, and the only way to enable protection was to start that Mac up in Recovery mode and use the csrutil command in the Terminal app there. That applied to macOS Sierra 10.12 to 10.12.1.

To make this easier, Apple changed csrutil so that it could enable SIP when invoked in normal running mode, provided it was run with elevated privileges obtained using sudo. Despite that, some of those affected MacBook Pro models didn’t have SIP enabled correctly for several months.

2017-18 Problems

Over the following years, SIP continued to cause irritations that infuriated some users.

Bundled apps in the main Applications folder were protected by SIP, and that prevented the user from modifying them. As the handling of kexts changed, it was discovered that SIP made it awkward to remove old kexts the user had installed. That was because the folder /Library/StagedExtensions was put under the protection of SIP by attaching a com.apple.rootless extended attribute to it.

One reading of that extended attribute is that only Apple’s KernelExtensionManagement service can give permission for changes to be made within that folder, and the folders within it.

2020 Extended attributes

Apple later used SIP to lock down individual extended attributes (xattrs) attached to regular unprotected files. The first example of this was the undocumented com.apple.macl xattr that macOS started to attach widely to all user documents. Presence of that xattr was implicated in some problems in which those documents became locked down and unable to save changes, despite permissions and other visible attributes showing that the user had full ownership of the file. The only workaround for this has been to copy the file to another volume, where the xattr no longer has the protection of SIP, and can be stripped.

When Apple later introduced another undocumented xattr com.apple.provenance, that too was sometimes but not always protected by SIP, although that hasn’t been implicated in problems visible to the user.

2022 Launch constraints

Launch constraints were introduced in macOS 13 Ventura and iOS 16 in 2022. Every executable binary in the system now has a set of rules determining the requirements for that binary to be launched. These include self constraints that the binary itself must meet, parent constraints that must be met by its parent process, and responsible constraints that must be met by the process requesting the launch. Together these form that code’s launch constraints. To make those constraints simpler, they come in different categories, ranging from 0, in which there are no constraints at all, to combinations that prevent launch by processes that aren’t themselves part of the system and require the code itself to be on the System volume.

Although Apple has documented these for developers, they can cause unexpected behaviour for users, who haven’t been given any explanation. Testing has demonstrated that launch constraints are dependent on SIP, so must be assumed to have been added to its list of protections.

2024 Malware scans

Many users have reported slowing app launch times in recent versions of macOS. In February 2024, Jeff Johnson investigated these, and concluded that the cause was the macOS security system repeatedly performed malware scans against a growing set of Yara rules. These stopped when SIP was disabled, implying that this is yet another protection that has been added to those controlled by SIP.

2024 Current protections

Current user documentation for SIP explains only its file system protection, csrutil‘s man page refers to its usage information, but from that and XNU it’s possible to separate out its controls to include the following, at least:

• Filesystem Protections, disabled by CSR_ALLOW_UNRESTRICTED_FS, abbreviated to fs
• Debugging Restrictions, disabled by CSR_ALLOW_KERNEL_DEBUGGER and CSR_ALLOW_TASK_FOR_PID, abbreviated to debug
• DTrace Restrictions, disabled by CSR_ALLOW_UNRESTRICTED_DTRACE, abbreviated to dtrace
• Kext Signing, disabled by CSR_ALLOW_UNAPPROVED_KEXTS, abbreviated in csrutil to kext
• NVRAM Protections, disabled by CSR_ALLOW_UNRESTRICTED_NVRAM, abbreviated to nvram
• Apple Internal, disabled in XNU by CSR_ALLOW_APPLE_INTERNAL, and only disabled when SIP is fully disabled
• BaseSystem Verification, abbreviated to basesystem
• Boot-arg Restrictions, disabled with nvram
• Kernel Integrity Protections, disabled with kext
• Authenticated Root Requirement, disabled by CSR_ALLOW_UNAUTHENTICATED_ROOT, managed separately using csrutil authenticated-root disable and enable
• Additional configuration flags available in XNU that don’t appear to be directly supported by csrutil include: CSR_ALLOW_TASK_FOR_PID, CSR_ALLOW_DEVICE_CONFIGURATION, CSR_ALLOW_ANY_RECOVERY_OS and CSR_ALLOW_EXECUTABLE_POLICY_OVERRIDE. Those should be disabled when SIP is fully disabled.

2015-2025 Vulnerabilities

Over the last decade, many vulnerabilities have been discovered in SIP that have allowed parts of its protections to be bypassed. Among the most recent is CVE-2024-44243 discovered by Jonathan Bar Or (@yo_yo_yo_jbo) of Microsoft Threat Intelligence and Mickey Jin (@patch1t), and fixed in the update to macOS 15.2 Sequoia. However, this wasn’t fixed in Sonoma until the following round of updates (14.7.3), and appears to remain unpatched in Ventura 13.7.8.

Microsoft’s report explains how bypassing just one of SIP’s many protections can give access to bypasses of more or all of SIP’s other protections. Note also how Apple’s description of the vulnerability in its security release notes refers to StorageKit but doesn’t reveal that this affected SIP.

Over the last decade, SIP has grown like Topsy from three protections that seemed worthwhile and simple, into a protean collection of many parts that remain largely undocumented and pervade much of modern macOS security.

References

Wikipedia’s account, still largely based on SIP in 2015
This blog on csrutil controls

Lovis Corinth wasn’t the only artist to have his own suit of armour. Rembrandt apparently bought at least one, while Jean-Léon Gérôme seems to have kept a suit hanging in his studio.

The End of the Pose (1886) is the first of Gérôme’s series of unusual compound paintings, which are at once self-portraits of him as a sculptor, studies in the relationship between a model and their sculpted double, and further forays into issues of what is seen, visual revelation, and truth.

Here, while Gérôme cleans up, his model is seen covering up her sculpted double with sheets, as she remains naked. Hanging against the wall behind is a complete suit of armour, and there is a single red rose on the wooden platform on which the model and statue stand.

Armour has occasionally been purely symbolic, most famously in the collaborative painting of Touch by Jan Brueghel the Elder and Peter Paul Rubens in their series The Five Senses from 1618.

Touch extends beyond its title to encompass other tactile sensory modalities. Heat is associated with a brazier, fine touch with brushes nearby. Much of the panel is devoted to a collection of armour, weapons, and their manufacture by gunsmiths and armourers. The many suits on display, seen in the detail below, appear to be equipment that isolates rather than stimulates the sense of touch.

During the nineteenth century, many painters looked back at the age of knights and chivalry, which inspired German Romantics, Pre-Raphaelites, and some of the last academic artists of the century.

The crusades presented Carl Friedrich Lessing with an ideal combination of mediaeval history, romance, and chivalry. In The Return of the Crusader from 1835, he shows a lone knight in full armour dozing as his horse plods its way up a path from the coast. Although his armour is still shiny, a tattered battle pennant hangs limply from his lance. This is based on a Romantic poem by the writer Karl Leberecht Immermann (1796-1840).

Edmund Blair Leighton’s Conquest from 1884 shows a stereotype knight in shining armour walking through an arch with its portcullis raised, a fair maiden walking behind him, as this victor enters the castle he has just conquered. The knight appears to be an idealised self-portrait.

Leighton’s The Accolade (1901) apparently shows Henry VI the Good – of Poland, not the British Henry VI – being dubbed a knight. Every link in his chain mail has been crafted individually.

Manuel García Hispaleto’s Don Quixote’s Speech of Arms and Letters (1884) shows the hero, his squire Sancho Panza behind, delivering one of his many orations after dinner, in a full suit of armour, as you would.

Eugène Delacroix visited tales of chivalry in his Combat Between Two Horsemen in Armour, painted at some time between 1825-30.

Plate armour continued to be worn by soldiers well into the twentieth century, and appears in some paintings of contemporary history.

Paul-Émile Boutigny’s undated Scene from the Franco-Prussian War shows soldiers from both sides of this short war in 1870-71. The soldier on the left is French, and holds a French Chassepot musketon with a long yataghan bayonet, while his colleague on the right appears to be Prussian, with his pickelhaube spiked helmet and a heavy cavalry cuirass that’s essentially modernised armour. (I’m grateful to Boris for his expert interpretation of this motif.)

François Flameng’s undated scene of Germans from the First World War shows the odd combination of archaic plate armour with modern gas masks.

Finally, as everyone knows, a knight goes to their grave in their armour.

Briton Rivière’s Requiescat from 1888 epitomises the faithful relationship between a dog and its master. As the knight’s body is laid out clad in armour, so his dog sits pining by the side of his body.

Sometimes even the best-kept Macs start acting strangely, and no matter what you try, you can’t put your finger on the problem, and can’t make it go away. This article suggests some potentially radical solutions that should address the most intransigent of problems in Apple silicon Macs.

Hardware?

If the problem lies in a peripheral, or the Mac’s hardware, then everything else is doomed to fail. Start by disconnecting all non-essential peripherals, and if that doesn’t help, run hardware diagnostics from Recovery mode. Those don’t always catch problems, particularly in their early stages, so if you’re not convinced that your Mac is sound and healthy, book it in for your nearest Apple store or authorised service provider to run their more extensive tests.

To run hardware diagnostics in an Apple silicon Mac, start it up in Recovery by pressing its Power button until it displays that it’s loading options, then in the initial Options screen, hold Command-D until the Diagnostics Loader starts. This may require download of the disk image from Apple’s servers before testing can proceed, so a good Wi-Fi connection is important. Once loaded, there’s a hidden option for extended diagnostics that can be triggered by holding the Command-E key combination.

What to reinstall?

At this stage with an Intel Mac, you’d be considering performing a clean reinstall of macOS, maybe even trying to revert to an older version that didn’t show the problem. Although you can still try that in Recovery mode, Apple silicon Macs have a better and more thorough option, to Restore the whole of your Mac’s firmware and macOS. This is performed by putting it into DFU mode, connected to another Mac (either architecture) running a recent version of macOS, and performing the Restore from there.

Apple provides detailed instructions for you to do this yourself, provided you have the necessary second Mac and cable. If you don’t have those, you should be able to get this performed free of charge at an Apple store, or by an authorised service provider.

The cable used mustn’t be Thunderbolt, but plain USB-C. That’s because DFU mode doesn’t support Thunderbolt or its cable. Connect that to the designated DFU port on the Mac you’re going to Restore. That can be found in Apple’s note, or in Mactracker.

You used to have to run Apple Configurator on the second Mac, but this can now be handled through the Finder, where it’s usually the more reliable. Follow Apple’s instructions to Restore the current version of the firmware and macOS, or you can download an IPSW image file for most previous versions through the links on Mr. Macintosh’s site.

Before performing this, you must make a full backup of your Mac’s internal storage, as the Restore process wipes it clean, and you’ll want to restore from that backup afterwards. As this process is going to wipe your Mac, you’ll also want to check through third-party apps and subscriptions that need to be signed out or transferred. Check carefully through the Applications folder to ensure that you haven’t forgotten any that are still valid. Among those is the need to deauthorise your old Mac for Apple media, something you should do using one of its media apps such as Music or TV.

Revive or Restore?

Apple advises trying to revive your Mac first, as it’s a briefer procedure and doesn’t wipe the whole of the Mac’s internal storage. However, if you’re trying to fix a deep-seated problem, only a full Restore will do.

What does a Restore do?

Internal storage in Apple silicon Macs contains additional partitions/containers to those found in Intel Macs or on external boot disks. These store the firmware and other components used early during the boot process, as part of Secure Boot. A ‘clean’ reinstall only replaces the boot volume group, the Signed System Volume (SSV) and Data volume, while a Restore in DFU mode wipes everything including the firmware, and replaces it with fresh copies from the IPSW file.

The end result is that your Mac is running the firmware to match the version of macOS installed, just as it would have been from the factory. It then has to be personalised and reconfigured from scratch once it’s started up. Nothing from its old firmware, macOS or Data volume is left, even the NVRAM, stored in NOR Flash memory, is reset.

Summary

• Hardware diagnostics in Recovery
• Consider extended diagnostics in Apple store
• Back up and prepare Mac
• Restore in DFU mode, using chosen IPSW if desired
• Restore from backup.

Armour, either in the form of plates of metal or chain mail with its many interlocked rings, is the primary attribute and symbol of the warrior. As such, several of the classical deities are often depicted wearing armour.

Peter Paul Rubens painted The Triumph of Victory in about 1614 for the Antwerp Guild of St George, its organisation of archers. Mars in his short suit of black armour dominates, his bloody sword resting on the thigh of Victoria, the personification of victory. She reaches over to place a wreath of oak or laurel on Mars, and holds a staff in her left hand. At the right, Mars is being passed the bundle of crossbow bolts that make up the attribute of Concord. Under the feet of Mars are the bodies of Rebellion, in the foreground, who still holds his torch, and Discord, on whose cheek a snake is crawling. The bound figure resting against the left knee of Mars is Barbarism.

Jacob Jordaens’ finished version of an original sketch by Rubens now known as The Golden Apple of Discord (1633) shows the wedding feast of the deities where Eris (Discord) makes her gift of the golden apple to set up the Judgement of Paris, leading to the Trojan War. At the left, Athena/Minerva, wearing her plumed helmet and a suit of ornate plate armour, reaches forward for that apple.

Just to confuse, the Roman goddess of war, Bellona (Greek Enyo), is also shown in or with armour by convention.

Peter Paul Rubens’ undated Portrait of Marie de’ Medici as Bellona shows her in the midst of cannon, arms and armour, with an exuberantly decorated helmet, a sceptre and a statue of a winged woman.

Armour inevitably plays a role in some of the events reported during the war against Troy. After his close friend Patroclus had been killed while wearing the armour of Achilles, he demanded a fresh suit made by Vulcan/Hephaestus before he would return to engage in battle.

Anthony van Dyck’s Thetis Receiving the Weapons of Achilles from Hephaestus from about 1630-32 shows the scene when Thetis is collecting her son’s new armour from Hephaestus, at the left.

Benjamin West’s Thetis Bringing the Armour to Achilles from 1804 shows the Greek warrior being presented with the armour and helmet by his mother Thetis.

When Achilles is killed in battle, in accordance with warrior tradition, his armour was handed on to the next in line, who could have been either Ajax or Odysseus.

Leonaert Bramer’s small painting on copper of The Quarrel between Ajax and Odysseus was made between about 1625-30. The pair stand in their armour, next to tents pitched at the foot of Troy’s mighty walls. At their feet is the armour of Achilles, and all around them are Greek warriors, some in exotic dress to suggest more distant origins.

Armour also leaked through into Christian religious paintings.

Lucas Cranach the Younger sets The Conversion of Saul (1549) in mediaeval northern Europe, with Paul and his party riding knightly chargers in their armour. Paul’s horse has fallen to the ground, with Paul still in the saddle rather than prostrate on the ground. Paul holds his hands up and looks to the heavens, where the figure of Christ is seen in a break in the clouds at the top left corner.

It was the young French martyr Joan of Arc, though, who is most often depicted wearing armour.

JAD Ingres painted Joan of Arc at the Coronation of Charles VII, in Reims Cathedral (1854). She stands close to the crown, resplendent in full armour and holding a standard, the two-pointed oriflamme embroidered for her by the women of Orléans, in her right hand.

The second scene in Jules Eugène Lenepveu’s Joan of Arc Murals (1886-90) shows Joan leading the French forces against the English, who were laying siege to the French city of Orléans. There had been controversy in Joan’s trial as to whether she had used weapons against the English; Lenepveu hedges here, showing her holding a sword in her right hand, but brandishing the Dauphin’s standard to rally the French, in the role that she described of herself. She’s wearing a suit of plate armour, which she was provided with in preparation for this operation. As this would have been designed to fit a man, this was part of the case against her for ‘cross-dressing’ in men’s clothes.

Lovis Corinth is one of several major painters who acquired themselves a suit of armour. This featured in two symbolic paintings made before and after the First World War.

When war broke out on 28 July 1914, Lovis Corinth and most of the other artists in Berlin shared an enthusiastic patriotism that initially gave them a buoyant optimism. He expressed this openly in his In Defence of Weapons from 1915.

Armour Parts in the Studio is Corinth’s summary of Germany’s defeat in 1918. The suit of armour is now empty, broken apart, and cast on the floor of his studio.

There are so many controls in macOS that sometimes you can’t see the wood for the trees. This can leave uncertainty over essentials, such as whether your Apple silicon Mac really is properly secure, or maybe there’s something sinister going on with it? This is a question I’m asked not infrequently, usually when someone has been spreading disinformation or FUD (fear, uncertainty, doubt). So how can you check that your Mac is properly locked down and boots securely?

Quick checks

There are two quick checks that cover the essentials. First, open System Information and select the Controller section in Hardware.

This provides a brief summary of your Mac’s boot security, which should read as shown above. If you still need to use a kernel extension or similar, your Mac might show Reduced Security with Allow All Kernel Extensions enabled, but you should do everything you can to avoid that.

Secure Boot is controlled using Startup Security Utility in Recovery mode, and if you care to start up in that mode, you can confirm or correct its settings there.

Back in normal user mode, open Privacy & Security settings and ensure you have FileVault enabled there.

SilentKnight also checks that XProtect/Gatekeeper checks are enabled, and that security data are up to date, giving you complete confidence.

Details

Although those should be sufficient for most, some want to go further and verify that their Mac’s boot process and security systems are also working correctly. To do that, shut your Mac down, wait ten seconds or so, and start up normally with the startup chime sounding at a known time. Enter your password, wait a few seconds for the Finder to get set up and running, and open LogUI. Set its time to that of the startup chime, and get the first 10 seconds or 10,000 log entries. You may need to adjust the seconds to capture the full boot sequence. When you have, look through the log and identify the following waypoints.

In each of these log entries, I have emboldened a word or two that you can copy from here and paste into LogUI’s Search box, then press Return. That will display the log entry, and sometimes others you might find relevant. Times are given here in seconds, with the startup chime occurring at about 37 seconds. Version numbers shown are those for macOS 15.6.

The start of boot is recorded as
37.562774 === system boot: [UUID]
and a little while after that, the kernel declares its version details
42.759300 Darwin Kernel Version 24.6.0: Mon Jul 14 11:30:40 PDT 2025; root:xnu-11417.140.69~1/RELEASE_ARM64_T6041
for macOS 15.6.

Further down you’ll come across more information about key security components, including the Trusted Execution Monitor
43.060422 [Log]: Code Signing Monitor Image4 Module Version 7.0.0: Fri Jul 11 16:51:29 PDT 2025; root:AppleImage4_txm-320.100.22~1090
43.060447 [Log]: build variant: txm.macosx.release.TrustedExecutionMonitor_Guarded-135.100.37

Then the iBoot firmware version
43.061758 iBoot version: iBoot-11881.140.96
43.061760 iBoot Stage 2 version: iBoot-11881.140.96

CoreCrypto support is vital, and another Image4 extension
43.137635 FIPSPOST_KEXT [133796636] fipspost_post:154: [FIPSPOST][Module-ID] Apple corecrypto Module v18.3 [Apple silicon, Kernel, Software, SL1]
43.242334 Darwin Image4 Extension Version 7.0.0: Mon Jul 14 11:23:46 PDT 2025; root:AppleImage4-320.100.22~2585/AppleImage4/RELEASE_ARM64E

You should see entries reporting the loading of security policy components
43.242343 Security policy loaded: AppleImage4 hooks (AppleImage4)
43.242961 Security policy loaded: Apple Mobile File Integrity (AMFI)
43.243092 Security policy loaded: Seatbelt sandbox policy (Sandbox)

The Secure Enclave Processor or SEP is another key component that has to be started up
43.264594 "AppleSEPKeyStore":326:0: starting (BUILT: Jul 14 2025 23:34:10) ("normal" variant 🌽 , 1827.120.2)
43.264639 "AppleSEPKeyStore":471:0: _sep_enabled = 1

Apple System Policy should follow a bit later
43.760156 Security policy loaded: Apple System Policy (ASP)
43.760188 AppleSystemPolicy has been successfully started

The root of the file system is then identified in two entries whose origins go right back to the start of Mac OS X
43.940643 BSD root: disk3s1
43.940644 , major 1, minor 13

And APFS mounts the root file system, using the SSV snapshot
43.941048 apfs_vfsop_mountroot:2984: apfs: mountroot called!
44.034685 apfs_vfsop_mount:2763: disk3s1 Rooting from snapshot with xid 1724240.

One of the most important entries comes shortly after that, where successful validation of the SSV’s root hash is reported
44.038830 authenticate_root_hash:642: disk3s1 successfully validated on-disk root hash

It’s now time to start user space processes, and for that launchd must be loaded so it can launch everything else
44.103761 load_init_program: attempting to load /sbin/launchd

How Secure Boot works

Apple silicon Macs have a small ROM to support DFU mode in case a full Restore is required, and to check and load the first stage of the ‘firmware’, the Low-Level Bootloader or LLB. Only if that matches its signature will the ROM firmware hand over to it and proceed with the boot process. The LLB in turn performs the same checks on the second stage ‘firmware’, iBoot proper. That goes on to check the kernel, before loading that and handing over for kernel boot to take over.

iBoot ‘firmware’ doesn’t write anything in the log, but once the kernel takes over its log entries provide a detailed account of its progress. The great majority of its log entries are unintelligible to anyone outside Apple, but the waypoints I have given above identify some of the most important steps it takes. When it’s ready, the kernel validates the root hash for the SSV snapshot, as noted above, enabling the boot process to proceed to load and run other parts of macOS. The remaining hash checking of the SSV, to confirm that it’s exactly as Apple intends, proceeds in a ‘lazy’ fashion, as access is needed to its contents.

This chain of validation before loading the next stage ensures that nothing in the boot process can be tampered with or changed, and the boot is secure throughout. Apple provides further details in its Platform Security Guide.

Apple has just released urgent security updates to bring macOS Sequoia to 15.6.1, Sonoma to 14.7.8, and Ventura to 13.7.8.

Security release notes for these are already available, for 15.6.1, 14.7.8 and 13.7.8 Each refers to the same single vulnerability in ImageIO, which is apparently being exploited “in an extremely sophisticated attack against specific targeted individuals” using a crafted image file.

The download for 15.6.1 is about 1.56 GB for an Apple silicon Mac, and should be well under 1 GB for Intel. Time to update!

Although there are a few still life paintings from classical Roman times, the first known in modern painting was made by Hans Memling in about 1485, and Caravaggio painting one in about 1599. There were precious few until after 1610, and it wasn’t until the Dutch Golden Age that they appeared in any quantity. Once they started, they quickly became popular, and may have accounted for as much as 10% of all paintings sold in Leiden, for instance. Their success was the result of religious intolerance.

Unlike the Italian Renaissance, the Flemish Renaissance revelled in the faithful depiction of surface textures and adventures in optics. Centres such as Antwerp trained painters in the skills needed, but Flanders and Brabant formed the Catholic Spanish Netherlands, where religious paintings were expected. Artists who followed the Reformed tradition rather than Catholicism or who wanted to paint secular works found themselves oppressed, and many migrated to the north, to paint in the Dutch Republic.

One of the most successful of the pioneer still life painters of the early seventeenth century was also a woman, Clara Peeters, and one of the finest still life painters of any age. We don’t even know when she was born, but she seems to have trained in Antwerp, then pursued her career successfully in the Dutch Republic. She’s thought to have been internationally successful by 1611, when at least four of her paintings were sold to Spain. Her last reliably-dated works are from 1621, although there are a few attributed to her from later.

Venetian Glass, Roemer and a Candlestick (1607) is one of Peeters’ earliest known works, which shows an extraordinary skill in rendering the varied surfaces and their optical properties. It is also one of the first still lifes in which the artist has included their own image reflected in the motif, here the base of the candlestick holder.

As in many still lifes, its contents have interesting symbolic meaning. The confectionery shown is sweet and ephemeral, the ring a sign of earthly riches and temporal relationships, the fly an indicator of earthly decay, and the burning candle combines remembrance with the strict limits on lifespan in this world. This is not just a still life, but an expression of vanitas, the futility and limits of our earthly existence, a theme for a separate article in this series.

Her paintings from 1611 that ended up in the Spanish Royal Collection, and are now in the Prado, move on from that impressive start.

This Table is laid out for a meal, with its range of food and surfaces with different optical properties. Settings for meals, particularly that of breakfast, were later to become a sub-genre in their own right.

Over the coming centuries, still life paintings featuring game were to become popular throughout Europe. Peeters’ Still Life with Game Piece and Poultry is their ancestor. Shells are another vanitas association.

Her Still Life of Fish and a Candlestick is one of the earliest and most accomplished paintings of the fruits de mer, which were to find favour with William Merritt Chase nearly three centuries later.

In the last of these from the Spanish collection, Clara Peeters makes another cameo appearance in its reflections, providing tantalising glimpses of herself.

The following year, her still life with Flowers and Gold Cups of Honour (1612) reveals multiple miniature self-portraits reflected in the gold cup at the right.

In her still life with Cheeses, Almonds and Pretzels from about 1615, her surface and optical rendering is breathtaking, and all thoughts of vanitas have gone. This is a celebration of the thoroughly earthly and sensuous pleasures of food. These are sustained in several of her other later paintings.

She hadn’t entirely forgotten the spiritual dimension, though. Another of her most interesting paintings returns to the concept of vanitas and the ephemeral.

Peeters established herself an international reputation, sold her paintings into major art collections, and pioneered what was to come in the rest of the century, yet is omitted from many accounts of painting in the Dutch Golden Age.

By this time, still life paintings were enjoying growing popularity in the buoyant market of the Dutch Golden Age. Ambrosius Bosschaert (1573–1621) painted this Flower Still Life in oil on copper in 1614, during the early years. He had been born in Antwerp, but because of the threat of religious persecution moved to Middelburg in the Dutch Republic, where he founded a school of floral painting.

At first its eclectic mixture of different flowers and flying insects appears haphazard. These merit a deeper reading, though: the flowers include carnation, rose, tulip, forget-me-nots, lilies of the valley, cyclamen, violet and hyacinth. These could never, at that time, have bloomed at the same time. The butterflies, bee and dragonfly are as ephemeral as the flowers around them. This too has more than a touch of vanitas.

By 1620, still life paintings were much in demand in northern Europe, and had ceased being occasional curiosities. Bosschaert’s career and family business was founded on the still life, which had come of age at last.

Collations of food grew ever more inventive, with Pieter Claesz combining a table of bread and delights in his Still Life with Musical Instruments from 1623. His underlying themes here are the rich browns of the food, wood and tortoise, and their curved forms. Claesz had been born near Antwerp, trained in that city and became a master there in 1620, when he too migrated to the Dutch Republic, where he established his studio in Haarlem.

Other artists developed the still life in the direction of food, as shown in Willem Kalf’s Still Life with Ewer, Vessels and Pomegranate from about 1645. He brings together an impressive variety of surface optical effects too, in this bravura display of technique.

Still life paintings pressed on into culinary exhibitions, usually centred on the breakfast table (ontbijtjes), which in Spain developed into bodegone, populated by caterers and their customers at roadside stalls.

Another fine example is Pieter Claesz’s Still Life with Salt Tub from about 1644, with its combination of bread, fish, sea salt, and an ornate glass goblet with its optical effects.

I’ve already shown some still life paintings including living creatures. Those developed into another sub-genre of dead game, which in turn linked to hunting and the depiction of wildlife.

Jan Weenix specialised in this sub-genre. His Still Life of a Dead Hare, Partridges, and Other Birds in a Niche from about 1675 is one of a large number of finely detailed and realistic paintings which he made. Weenix was born in Amsterdam, where he lived and worked for much of his life, but was a Catholic who worshipped in ‘hidden’ churches that were tolerated in the Dutch Republic.

These piles of animal corpses spilled out into a strangely dark countryside, in paintings such as his Still Life of Game including a Hare, Black Grouse and Partridge, a Spaniel looking on with a Pigeon in Flight from about 1680. These became popular at the time, and Weenix was commissioned to decorate the houses of the rich with large murals on canvas, and to paint series for European royal courts. The more ostentatious paintings were known as pronkstilleven.

Others used the still life as a link to what later became natural history painting.

For their familiarity, bright colours, and natural beauty, butterflies were popular in the Dutch Golden Age, particularly in smaller paintings such as still lifes destined for the collector’s cabinet. Nicolaes de Vree’s undated Forest Floor Still Life with Flowering Plants and Butterflies from the latter half of the seventeenth century is a fine example of a painting that goes beyond the normal still life and depicts a more natural scene.

Still life painting during the Dutch Golden Age flourished and brought commercial success to many artists. It also laid the foundations for several sub-genres which were to be developed later. Far from being the lowest of the genres, for around a century in the Dutch Republic they were among the most innovative and exciting.

Security utilities that detect known malicious software do so using sets of detection rules. Since their introduction by Victor Alvarez of VirusTotal 12 years ago, the most common method of expressing these rules is in a text file with the extension .yara. Apparently YARA stands for either YARA: Another Recursive Acronym, or Yet Another Ridiculous Acronym.

Yara rules are used extensively in macOS by both the original XProtect and its sibling XProtect Remediator. Those of XProtect are found in the XProtect.yara file in XProtect.bundle, in /Library/Apple/System/Library/CoreServices and its additional location in /private/var/protected/xprotect in Sequoia and later. Further Yara rules are also encrypted and embedded in XProtect Remediator’s scanning modules, as detailed by Koh M. Nakagawa in the FFRI Security GitHub.

As used by Apple, each rule can consist of up to three sections:

• meta, containing the rule’s metadata including a description and in more recent cases a UUID for the rule.
• strings, specifying some of the content of the file, typically in the form of hexadecimal strings such as { A0 6B }.
• condition, a logical expression that, when satisfied, meets the requirements of that rule, so identifying it as malicious.

I’ll exemplify these using Yara rules used in XProtect version 5310.

Private rules

At the start of the Yara file are any private rules. These are a bit like macros, in that they define properties that are then used in multiple rules later. Laid out in compact form, an example reads:

private rule Shebang
{ meta:
description = "private rule to match shell scripts by shebang (!#)"
condition:
uint16(0) == 0x2123
}

This starts with description metadata for this private rule, then states the condition for satisfying this rule, that the first 16-bit unsigned integer in the file contains the hex 0x2123, the UTF-8 characters 0x21 or ! and 0x23 or #. In the reverse order of #! they’re known as the shebang, and the opening characters of many shell scripts, but in this rule they are given the other way around because of the byte order used in the 16-bit integer.

This defines what’s required of a Shebang, and can be included in the conditions of other Yara rules. Instead of having to redefine the same feature in every rule, they can simply include that Shebang rule in their condition.

Regular rules

After 3-5 private rules, the XProtect Yara file goes on to enumerate 372 normal rules, including this one:

rule XProtect_MACOS_SOMA_JLEN
{meta:
description = "MACOS.SOMA.JLEN"
uuid = "4215C9D4-57D5-4D30-82E1-96477493E8D5"
strings:
$a0 = { 4c 8d 3d ?? 74 0b 00 4c 8d 25 ?? ?? 0b 00 4c 8d 2d ?? ?? 0b 00 48 8d 5d c0 }
$a1 = { 73 62 06 91 d4 03 00 f0 94 42 21 91 }
condition:
Macho and ( ( $a0 ) or ( $a1 ) ) and filesize < 5MB
}

This rule has its internal code name as its description, and has been assigned the UUID shown. It then defines two binary strings, a0 and a1, the former containing ‘wild’ values expressed using the question mark ?. The condition for satisfying the rule is that the file must:

• be a Mach-O binary, and
• contain either a0 or a1, and
• its size must be less than 5 MB.

Further details about Yara rules are given here.

Implementation

There are standard implementations that can check files against custom sets of Yara rules. Rules are normally compiled into binary form from their text originals before use. Full details are given on VirusTotal.

Apple’s use of Yara files is mysterious, as for some years all the descriptions used arbitrary code names as obfuscation. When the source of all the rules is given in plain text, it’s hard to see what purpose that served, and it meant that users were told that MACOS.0e32a32 had been detected in an XProtect scan, for instance. Thankfully, Apple has more recently replaced most of those with more meaningful names.

I’m grateful to Duncan for asking me to explain this, and hope I have been successful. I’m also grateful to isometry and an anonymous commenter for straightening out the confusion over the Shebang.

Apple has just released an update to XProtect for all supported versions of macOS, bringing it to version 5311. As usual, Apple doesn’t release information about what security issues this update might add or change.

This version adds eight new detection rules, for MACOS.BANSHEE.MA, MACOS.BANSHEE.MA2, MACOS.SOMA.GEGO, MACOS.POSEIDON.B, MACOS.TIMELYTURTLE.FUNA, MACOS.TIMELYTURTLE, MACOS.TIMELYTURTLE.INDRBYSE and MACOS.TIMELYTURTLE.INDR. Banshee, Poseidon and TimelyTurtle are new names in XProtect’s Yara rules.

You can check whether this update has been installed by opening System Information via About This Mac, and selecting the Installations item under Software.

A full listing of security data file versions is given by SilentKnight and SystHist for El Capitan to Tahoe available from their product page. If your Mac hasn’t yet installed this update, you can force it using SilentKnight or at the command line.

If you want to install this as a named update in SilentKnight, its label is XProtectPlistConfigData_10_15-5311

Sequoia and Tahoe systems only

This update has already been released for Sequoia via iCloud. If you want to check it manually, use the Terminal command
sudo xprotect check
then enter your admin password. If that returns version 5311 but your Mac still reports an older version is installed, you may be able to force the update using
sudo xprotect update

Unlike watercolour, oil paint ‘dries’ by an irreversible process of chemical polymerisation. Once ‘dried’ it resists solvents and can be painted over without any risk of its pigments mixing between layers. Unlike modern acrylic paints, oil paint usually takes at least a week or two before its surface is dry, so allows the painter to control mixing of an existing layer with fresh paint. Skilful control of paint viscosity and drying rate thus gives fine control over the softness of edges and their blurring or sharpness.

This is illustrated well in Lucas Cranach the Elder’s portrait of Salome with the Head of Saint John the Baptist from about 1530. Crisp edges appear where you expect, for example between skin and clothing. In some places, he also outlined edges with thin lines of dark shadow for emphasis. Where skin tone changes more subtly, and in Salome’s eyebrows, there are soft transitions achieved by painting wet on wet and blurring the edge, a technique often known as sfumato, as seen in the detail below.

Cranach and the staff of his workshop would have worked on that painting over a period of many weeks to achieve those effects. In contrast, sketching with oil paints in front of the motif is far simpler, and on a more modest scale. Because of constantly changing light and shadow, most proficient landscape artists aim to complete their oil sketches in under two hours, and an hour is ideal.

Robert Henri’s Landscape Sketch at Escorial (1906) was painted on a wooden pochade panel, almost certainly in a single short session outside the city of Madrid, in the hills near the Escorial. Although he used the viscosity of different paints to make its skyline sharp, you can see where his coarse brushstrokes have been applied and colours mixed and laid in streaks.

The young Canadian artist Tom Thomson excelled in rapid sketching in oils, with several witnessed accounts of him dashing off a painting in little more than fifteen minutes. As a result he was able to capture many transient effects, such as the passing thunderstorm in Thunderhead from 1912-13. He has found it harder to keep a crisp skyline, and clearest separation of paint is in the white masts of the boats at the edge of the water. Those were painted last, in single strokes with as little diluent as possible.

Before the nineteenth century, quick oil sketches were almost never shown to the public, but used by masters including Valenciennes and Constable purely as preparative studies. When fashions changed, it became acceptable if not desirable for paintings to look sketchy and rushed, although appearances can sometimes be deceptive.

Some masters of fast painting used these skills in multiple sessions, to increase the amount of detail they could incorporate into a landscape. When Pissarro suffered from eye problems late in his career, he painted from rooms with views over the streets of Paris, and produced some of his finest cityscapes.

Boulevard Montmartre, Spring Morning (1897) is composed primarily of buildings and streets, a plethora of figures, and countless carriages to move those people around, the ingredients for so many of his late paintings.

In the foreground, Pissarro may have formed each quite roughly, but he has painted in sufficient detail. Three white horses range in tone and colour, with highlights on the front of each head. You can see which people are wearing hats, and spot ladies in their fashionable clothing.

Deeper into the distance, detail is lost, and the carriages and crowds merge into one another. Still they have a rhythm, highlights and shadows, and form. He must have spent day after day at his hotel window populating these busy streets.

Other Impressionist paintings appear at first sight to have been painted quickly in front of the motif, but were more likely worked on over a period of months in the studio. Once the public had come to expect an Impressionist painting to look as if it had been painted quickly, they expected the same look even though some paintings may have required several months painting.

Monet’s Flowering Plum Trees (1879), for example, has a complex structure in its paint layer, as seen from the surface in the detail below. Some marks have been added wet-in-wet, but many wet-on-dry, demonstrating it must have been worked on over a period of weeks or months.

The myth about Monet’s Grainstacks series is that they depict transient effects of season, weather, and light, as they were painted en plein air over the course of the winter. Looking at all twenty-five, I have long had my doubts, and suspect that Monet spent a lot of the time prior to their exhibition making further changes to them. This in no way lessens Monet’s sublime achievement, nor their art in any way. It’s just that they aren’t quite the paintings described by the myth that has grown around them.

Looking at Grainstacks, End of Summer, considered to be one of the earliest in the series and numbered 1266, the trees behind the two grainstacks are still in full summer leaf, with no indication of the advent of autumn. Yet Monet’s signature gives the year as 1891. Looking at its paint surface in detail (below), some has been applied wet-in-wet and blended with underlying and adjacent paint, but many other brushstrokes have clearly been applied over dry underlayers.

The blue-grey shadow of this grainstack was applied with relatively dilute paint wet-on-dry over thicker off-white paint with marked surface texture. However, that off-white paint has itself been applied wet-on-dry over a pale green layer. This couldn’t have been achieved in the same day, even when the ambient temperatures were warmer during the early autumn, but probably reflects at least three sessions with drying time in between them.

Grainstack, Sun in the Mist, numbered 1286, is thought to be one of the later paintings in the series, apparently showing the sole remaining grainstack in the Spring of 1891. It too has multiple layers applied wet-on-dry, with many hatched brushstrokes in shades of orange and pink apparently applied over a well-dried surface. These are again shown well in the detail (below) of the grainstack itself.

At the right side of the foot of the grainstack, the lowest layer of paint consists of dull blue and green that appear to have been applied at about the same time and have blended in places. When that layer had dried, infrequent and relatively thick streaks of white were added wet-on-dry. When that had dried, brown-orange was applied to form the uppermost layer. That uppermost layer has also been used to remodel the form of the grainstack using thickly-applied flesh, pale yellow and orange paint.

The evidence points to Monet starting each of this series with a sketch using more dilute paint in front of the motif in the circumstances described in the title. He then brought each canvas into his studio, where he continued to work on it, making further adjustments, adding partial layers of paint, and tweaking each work in comparison to the others in the series. This would have taken place over a period of several weeks: in the case of the canvases that he had started at the end of the summer of 1890, such as W1266 above, that period could have amounted to six months.

That may well have been longer than the time taken by Cranach to paint Salome.

For many of us, Live Text and Visual Look Up are real boons, making it simple to copy text from images, to perform Optical Character Recognition (OCR) on images of text, and to identify objects of interest. They are also used by the mediaanalysisd service to extract text and object identifications for indexing by Spotlight, making those image contents searchable. Although the latter can be disabled generally or for specific folders in Spotlight settings, there appears to be only one control over Live Text, and none for Visual Look Up. This article examines what that single control does, using log extracts obtained from a Mac mini M4 Pro running macOS Sequoia 15.6. It follows my recent article on how these features work.

Setting

Live Text, which is enabled by default, can be disabled in Language & Region settings. When that is turned off, opening an image containing text in Preview no longer makes any text selectable. However, Visual Look Up still works as normal.

Textual images

When an image containing recognisable text but no other objects is opened in Preview, the VisionKit subsystem is still activated soon after the image is loaded. VisionKit initially reports that the “device” supports analysis, but immediately clarifies that to
Device does not support image analysis, but does support Visual Search, limiting to just Visual Search.
It then starts a VKImageAnalyzerProcessRequestEvent with a MAD parse request. That leads to a Visual Search Gating Task being run, and the Apple Neural Engine (ANE) and all CPU P cores are prepared for that.

Less than 0.1 second later, the end of the VKImageAnalyzerProcessRequestEvent is reported, and VisionKit returns an analysis that no image segments merits further analysis. Preview’s ⓘ Info button remains in its normal state, and clicking on that doesn’t alter the image displayed.

Images with other objects

An image containing potentially recognisable objects doesn’t stop there. If VisionKit returns an analysis indicating Visual Search could extract objects from the image, the ⓘ Info button adds stars and waits for the user to open the Info window.

VisionKit reports in the log
Setting Active Interaction Types: [private], [private]
then that it
DidShowVisualSearchHints with invocationType: VisualSearchHintsActivated, id: 1

When one of those Visual Search Hints is clicked, the Lookup View is prepared, followed by a notice from LookupViewService that it’s Changing state from LVSDisplayStateConfigured to LVSDisplayStateSearching. That leads to VisionKit making a Visual Search request from mediaanalysisd.

After the Apple Neural Engine (ANE) is run to progress that, successful search results in PegasusKit making its internet connection to identify the object, exactly as it does when Live Text is enabled and text has been recovered from the image:
Querying https: // api-glb-aeuw1b.smoot.apple.com/apple.parsec.visualsearch.v2.VisualSearch/VisualSearch with request (requestId: [UUID]) : (headers: ["Content-Type": "application/grpc+proto", "grpc-encoding": "gzip", "grpc-accept-encoding": "gzip", "grpc-message-type": "apple.parsec.visualsearch.v2.VisualSearchRequest", "X-Apple-RequestId": "[UUID]", "User-Agent": "PegasusKit/1 (Mac16,11; macOS 15.6 24G84) visualintelligence/1", "grpc-timeout": "10S"]) [private]

The ANE is finally cleaned up and shut down as the search results are displayed in the Lookup View.

Conclusions

• When Live Text is disabled in Language & Region settings, images are still analysed when they are opened, to determine if they’re likely to contain objects that can be recognised in Visual Search for Visual Look Up.
• If there are no such objects detected, VisionKit proceeds no further.
• If there are suitable objects, mediaanalysisd and VisionKit proceed to identify them using Visual Search Hints, as normal.
• If the user clicks on a Visual Search Hint, PegasusKit connects to Apple’s servers to identify that object and provide information for display in the Lookup View.
• Although there is less extensive use of the ANE and CPU cores than when Live Text is enabled, neural networks are still run locally to perform a more limited image analysis.

I’m very grateful to Benjamin for pointing out this control over Live Text.

In the First Circle of Hell, Dante and his guide Virgil saw the souls caught in Limbo. From there they descend to the Second Circle, where they find those guilty of the sin of lust. They pass the figure of Minos, who extracts a confession from every sinner as they begin their descent, and directs them onward to the appropriate circle for their sins.

Here the light is dim, and there is an eternal storm blowing those in this circle, ensuring they never obtain any comfort or relief from its incessant blast. The first of those described by Virgil to Dante is Semiramis, who married her father and made such incestuous relationships legal. (This is now known to be a false legend recorded by Orosius, popular in Dante’s time.)

Then they see Cleopatra, Achilles, Paris and Tristan. Dante tells the story of Francesca in most detail, and possibly for the first time in literature. She appears, blown in the wind, with her lover Paolo, but it’s Francesca who speaks to Dante.

Francesca da Rimini was the aunt of Dante’s host when he lived his later years in Ravenna. In about 1275, she married Gianciotto of the ruling family in Rimini, for political reasons. There’s strong suspicion that she had been tricked into this: her husband turned out to be disfigured and uncouth, but pre-nuptial negotiations were conducted by his handsome and eloquent brother Paolo, suggesting she was duped.

Soon after the marriage, Paolo and Francesca became lovers, apparently inspired by the story of Lancelot and Guinevere. Gianciotto suspected the couple, and one day caught them together in his wife’s bedroom.

Paolo had become stuck when trying to escape through a trapdoor. Francesca was unaware of that, and let her husband in, who then attacked his brother with his sword. But Francesca stepped in between them to save her lover and was killed; Gianciotto then killed his brother, and after his own death had descended further into Hell for that double murder.

Dante’s story has inspired a succession of masterly paintings.

It was William Blake’s Whirlwind of Lovers that transformed these depictions.

This story is told in Dante Gabriel Rossetti’s watercolour triptych: at the left, the lovers are reading the legend of Lancelot and Guinevere. In the centre are Dante and Virgil, and at the right Paolo and Francesca are being blown in the storms of the Second Circle of Hell.

Dante faints at the tragic story that Francesca has told him, and collapses as if dead.

The artists

William Blake (1757–1827) was a British visionary painter and illustrator whose last and incomplete work was an illustrated edition of the Divine Comedy for the painter John Linnell. Most of his works shown in this series were created for that, although he did draw and paint scenes during his earlier career. I have a major series on his work here.

Umberto Boccioni (1882–1916) was an Italian painter and sculptor whose tragically short career was a major influence over the development of Futurism. Drafted into the Italian Army during the First World War, he was thrown from his horse and trampled to death when he was only thirty-three.

Alexandre Cabanel (1823–1889) was a major French painter of history in an academic style, and a precocious artist. He won the Prix de Rome in 1845, and was appointed a professor at the École des Beaux-Arts in Paris in 1864, teaching many successful pupils including Jules Bastien-Lepage. This article summarises his career and work.

Gustave Doré (1832–1883) was the leading French illustrator of the nineteenth century, whose paintings are still relatively unknown. Early in his career, he produced a complete set of seventy illustrations for translations of the Inferno, first published in 1857 and still being used. These were followed in 1867 by more illustrations for Purgatorio and Paradiso, and this painting was highly praised when shown at the Paris Salon in 1863. This article looks at his paintings.

Giuseppe Frascheri (1809–1886) was an Italian painter in fresco and oils who has been almost completely forgotten.

Jean Auguste Dominique Ingres (1780–1867) was a major French painter in Neoclassical style, best known for his history and other narrative paintings. He was a pupil of Jacques-Louis David, and continued much in his tradition, and in opposition to the more Romantic painting of Eugène Delacroix. His work extended from portraits to Orientalism.

Gaetano Previati (1852–1920) was an Italian painter who worked mainly in Divisionist style, but is now known for his Symbolism. He was most famous in the period 1880-1920, during which he was involved in the Venice Biennale and exhibitions in Italy and Paris.

Dante Gabriel Rossetti (1828–1882) was of Italian descent but born in London. In 1848, he co-founded the Pre-Raphaelite Brotherhood, and was a major figure in British painting until his early death in 1882. A published poet and author himself, many of his paintings were in response to literature, particularly the poems of John Keats. He had a succession of relationships with his models and muses, including Elizabeth Siddal, Fanny Cornforth, and William Morris’s wife Jane. The triptych shown here is the earliest of at least three paintings of his showing Paolo and Francesca, another similar triptych being from 1862.

Ary Scheffer (1795–1858) was a major narrative painter of the first half of the nineteenth century, born in the Netherlands but trained and working in Paris. Among his favourite literary themes were Goethe’s Faust, and the story of Paolo and Francesca. This article looks at his narrative work.

George Frederic Watts (1817–1904) was a major British painter and sculptor in the middle and late nineteenth century who was associated with several artistic circles and movements including the Pre-Raphaelites, but who worked independently in more Symbolist style. This article looks at his career and paintings.

References

Wikipedia
Danteworlds

Robin Kirkpatrick (trans) (2012) Dante, The Divine Comedy, Inferno, Purgatorio, Paradiso, Penguin Classics. ISBN 978 0 141 19749 4.
Richard Lansing (ed) (2000) The Dante Encyclopedia, Routledge. ISBN 978 0 415 87611 7.
Guy P Raffa (2009) The Complete Danteworlds, A Reader’s Guide to the Divine Comedy, Chicago UP. ISBN 978 0 2267 0270 4.
Prue Shaw (2014) Reading Dante, From Here to Eternity, Liveright. ISBN 978 1 63149 006 4.

I hope that you enjoyed Saturday’s Mac Riddles, episode 321. Here are my solutions to them.

1: Where to sell an image of the Knolls in a two-year exclusive.

2: Rembrandt, Claude Monet, JMW Turner and Corel.

3: One of the first two, it could be beige acrylic and written by Bill.

The common factor

I look forward to your putting alternative cases.

There are some topics that invariably generate comments from those who have either abandoned a major feature in macOS, or are struggling with it. Some of the most persistent are problems with Spotlight, particularly with its local search of files on your Mac. To help grapple with those, four years ago I added some Spotlight tests to Mints that can be used to work out where those problems are occurring. I’m delighted now to offer an extension to those in a whole new app, perhaps predictably named SpotTest.

Spotlight is so substantial, almost silent in the log, and impenetrable that the best approach to diagnosing its problems is to test it out in a controlled way. Mints has been doing that by creating a folder of files containing an unusual word, then searching for that. Although that’s still useful for a quick test, we need something more focused and flexible, and that’s what SpotTest aims to deliver.

Following deep dives into how Spotlight indexes and searches metadata and contents of files, and how it can search text extracted from images and the results of image analysis, I’ve realised that different test files are required, together with alternative means of search. For example, the standard approach used in compiled apps, with NSMetadataQuery, is incapable of finding content tags obtained using Visual Look Up, which only appear when using the mdfind command. SpotTest takes these into account.

There are now 15 carefully crafted test files, of which one cannot currently be found, no matter what method of search you try.

A perfect 13/15 result from NSMetadataQuery is only possible after waiting a day or more for background mediaanalysisd processing to recognise and extract the text in file I, a PNG image. The other 12 here should all be found when running this test a few seconds after the test files have been created. They rely on a range of mdimporter modules bundled in macOS, apart from file L, an XML property list.

Another of SpotTest’s tools will list the mdimporters used for each of the test files.

Run the search using the mdfind command within SpotTest and, once mediaanalysisd has done its image recognition, you should get a perfect 14/15.

The only current limitation of SpotTest version 1.0 is that it can only run tests on the Data volume that your Mac started up from, using a folder at the top level of your Home folder. A future version will let you test other volumes as well. Its Help book runs to nine pages: please read them, as its test might seem deceptively simple but provide a lot of useful information about how Spotlight local search is functioning. Coupled with log extracts using LogUI it should shine light in the darkness.

SpotTest 1.0, which requires macOS 14.6 or later, is now available from here: spottest10
and from its new place in its Product Page.

I wish you successful searching.

The element chromium gains its name from the rich colours seen in many of its salts and compounds. One of them, chromium oxide, was discovered in about 1798 by Louis-Nicolas Vauquelin, who immediately recognised its future use as a pigment, because of its “fine emerald colour”. But painters were still enamoured with more toxic greens, and straight chromium oxide doesn’t look particularly brilliant, being a rather dull yellow-green. Its introduction into paintings probably didn’t start until around 1840, when landscape painting outdoors was becoming all the rage.

Some of the earliest paintings known to use chromium oxide are those of Moritz von Schwind, of which the first example that I can show is his Mermaids Watering a Stag from about 1846. He seems to have used the pigment quite extensively here in foliage, although probably in combination with other pigments.

Von Schwind’s King Krokus and the Wood Nymph from about 1855 is a clearer image, where he probably used chromium oxide in combination for most of his greens.

As these works were being painted, an improved version of chromium oxide was being developed: hydrated chromium oxide, which became known as viridian during the 1860s. This first became available at a reasonable price after Guignet started to make it in quantity in 1859, so has also been known as Guignet’s green. It’s sometimes termed émeraude or emerald, which only serves to confuse viridian with copper acetoarsenate, more widely known as emerald green.

Viridian came into use during the 1860s, and has proved far more popular than chromium oxide. Both pigments are reliably lightfast, opaque, and have good covering power, but viridian is the more intense, and doesn’t appear dull like plain chromium oxide.

Anselm Feuerbach’s painting of Paolo and Francesca from 1864 is one of the earlier works found to contain viridian among its many rich greens.

The best example showing off the colour of viridian is perhaps Édouard Manet’s The Balcony (1868-69), where he appears to have used the pigment throughout the blinds and railings, most probably mixed with lead white, and unmixed for the woman’s parasol.

Arnold Böcklin’s Triton and Nereid from 1874 is unusual in several respects. It’s reported as being painted in tempera rather than oils, but its deep lustrous greens were developed using a base of predominantly viridian, over which Böcklin applied a copper resinate glaze.

Pierre-Auguste Renoir’s La Yole (The Skiff) of 1875 uses viridian as the main colour for the reeds in the left foreground.

Analysis of Claude Monet’s series of paintings of the Gare Saint-Lazare in 1877 has revealed extensive use of viridian in mixtures, including the green shadows in the roof. In Arrival of the Normandy Train, Gare Saint-Lazare (1877), the pigment is apparent (and confirmed) throughout the green foreground of the platform, an optical effect resulting from light passing through the glass roof of the station.

Renoir used viridian together with malachite green and other pigments for the greens in his Chrysanthemums (1881-82).

If you care to spend some time examining the myriads of tiny dots in Georges Seurat’s monumental Divisionist painting of A Sunday Afternoon on the Island of La Grande Jatte (1884-86), I’m assured that you’ll find many of those forming its vegetation contain viridian.

Viridian remained popular among the post-Impressionists, from whom I have two well-known paintings as examples.

Vincent van Gogh included viridian in the pigments used in the range of greens in his A Wheatfield, with Cypresses (1889), which is more unusual for his use of ultramarine blue mixed to form green.

Paul Cézanne is known to have had a strong preference for viridian as one of the key colours in his palette. However, in his Hillside in Provence (1890-92), it is emerald green that is the more prominent, and the major part of the painting’s more brilliant greens, even into its pale turquoise sky. Some green passages, such as the patch of yellow-green grass at the edge of the path in the foreground, at the right edge of the canvas, have been built with a base of lead white and viridian, over which he has applied a yellow lake glaze.

Chromium oxide and viridian remain widely available today; although the former is not popular or widely used, viridian remains a mainstay green widely recommended for its colour and other properties. Being virtually insoluble, chromium oxide and viridian pose minimal risks of toxicity to the artist. However, there is growing concern over their environmental effects, and great care is needed when handling waste paint containing either pigment.

Reference

Richard Newman (1997) Artists’ Pigments, vol 3, ed Elisabeth West FitzHugh, Archetype. ISBN 978 1 904982 76 0.

If there’s one thing you can rely on about the UK weather, it’s rain. Unless you live in that narrow belt of East Anglia officially classed as semi-arid, you’ll be used to rain whatever the season or forecast.

The last time we had a long dry summer was 1976, when much of Northern Europe basked in sunshine from late May until the end of August. This year has proved similar, so here we are again, dry as a bone, banned from using hosepipes except to wash down horses, wondering when the inevitable floods will start. In 1976, dry weather broke but a couple of weeks after the appointment of a Minister for Drought, whose brief was promptly extended to cover the ensuing inundation.

With this shortage of water, it might seem surprising that over the next five years around a hundred new data centres are expected to be built in the UK. These are the data centres we all want to support our AI chatbots and cloud services, but nobody wants in their neighbourhood. No one has explained where all their power and water supplies will come from, although apparently ten new reservoirs are already being built in anticipation.

The best piece of advice we have been given to help our shortage of water is to delete all our old emails and photos. Apparently by reducing what we have stored in the cloud, those data centres won’t get so hot, and will consume less water. Really?

Meanwhile back on planet Earth, last week I was studying the log entries made on behalf of the Apple Neural Engine, ANE, inside my Mac mini’s M4 Pro chip, when it was running local models to support Live Text and Visual Look Up. We now take these features for granted, and maybe aren’t even aware of using them, or of what our Mac’s ANE is doing. Yet every Apple silicon Mac sold over the last five years has the dedicated hardware possessed by only a small minority of PCs. They can, of course, use other hardware including GPUs, well known for their excessive power and cooling demands. For many the only solution is to go off-device and call on some of those data centres, as you do with ChatGPT, Google’s answer engine, and even Elon Musk’s Grok if you really must.

Live Text is a particularly good example of a task that can, given the right hardware, be performed entirely on-device, and at relatively low energy cost. It’s also one that many of us would rather not farm out to someone’s data centre, but keep to the privacy of our own Mac. While it does work surprisingly well on recent Intel Macs, it’s just what the ANE was intended to make sufficiently performant that it can be commonplace. Just over three years ago, before WWDC 2022, I wrote: “But if I had to put my money anywhere, it would be on the ANE working harder in the coming months and years, to our advantage.”

With so many Macs now capable of what seemed miraculous in the recent past, we’re only going to see more apps taking advantage of those millions of ANEs. Developers are already starting to use Apple’s new Foundation Models supported by macOS 26 Tahoe, all of which run on-device rather than in those data centres. In case you’re concerned about the ethics of what this might be unleashing, Apple has already anticipated that in a stringent set of acceptable use requirements, that also apply to apps provided outside the App Store.

Obtaining reliable estimates of the performance and power consumption of the ANE is fraught, but I have measured them during Visual Look Up on an M1 Max (with an H11ANE), and found peak power used was 30-50 mW. According to mot’s comment to that article, when running an inference task intended to push that in an M1 Pro to the maximum, its ANE drew a maximum of 2 W. That’s frugal compared to running equivalent intensive tasks on Performance CPU cores or an Apple silicon GPU, which can readily use more than 1 W per P core.

Can someone suggest that, instead of deleting old emails and photos, we’d be better off running our favourite AI on-device using an Apple Neural Engine? I still don’t think it would do anything to help our current drought, but it could spare us a few of those projected data centres.

Rumours still abound as to the cause of Napoleon’s death over two centuries ago. One theory, not currently in favour, is that he was poisoned by arsenic in the wallpaper. At the time, that would have been unusual, but by the 1860s such deaths were significant enough to be reported in newspapers. Their ultimate cause was also one of the factors behind the success of Impressionist landscape painting: emerald green.

Getting a good range of green pigments was vital for landscape painting, and more generally for coloured commercial products such as wallpaper and clothing. The first of the ‘poison greens’ to be discovered was that named after Carl Wilhelm Scheele, the Swedish chemist who originally made it in 1775: copper arsenite, a highly toxic salt of arsenic. Soon after its introduction from about 1780, it became clear that it tended to darken with age, and the search began for a replacement.

Little attention has been paid to the use of Scheele’s green, and it isn’t clear how widely it was used, or even when it was first used in painting.

JMW Turner’s early oil sketch of Guildford from the Banks of the Wey, painted in about 1805, has been found to contain Scheele’s green. Given its range of greens, that could be quite extensive.

Wilhelm Sattler, a paint manufacturer in Schweinfurt, Germany, worked with Friedrich Russ to discover an even better arsenic compound for use as a colourant, and from 1814 Sattler’s company manufactured Schweinfurt or emerald green, the equally toxic copper acetoarsenite. Its alluringly brilliant green colour appears very stable, with only slight darkening resulting from reaction with hydrogen sulphide, a common atmospheric pollutant.

By about 1830-32, when Turner painted Going to School as an illustration for Rogers’s Poems, he had switched to using emerald green, obvious from its characteristic colour standing out from the small bag on the boy’s back.

Turner used emerald green again in this watercolour painting of Rouen, Looking Downstream from about 1832, here in combination with other pigments, so less brashly.

Concerns over the established toxicity of these two greens were raised by 1839, when warnings were first issued in Bavaria. Despite those, the use of emerald green became more widespread, and it was even ‘fixed’ to ball gowns using albumen or dextrin, which allowed its poisonous dust to brush free from the garment when dancing. It also became particularly popular, and insidiously toxic, in coloured wallpapers. When applied on damp walls, as were common at the time, fungal products could produce trimethyl arsine gas, which is thought to have been responsible for many of the symptoms and deaths that were reported.

Édouard Manet’s Music in the Tuileries (1862) is an unusual example of a painting containing both Scheele’s and emerald greens. Manet used them in combination in two different glazes applied to the areas of foliage. In one transparent glaze, they are mixed with yellow lake, small amounts of ivory black, and yellow ochre; the other more opaque glaze consists of the two greens, with yellow ochre and white.

The last recorded use of Scheele’s green was by Edwin Landseer in 1866.

The Impressionists relied heavily on emerald green for its brilliance and intensity of colour. Frédéric Bazille’s Self-Portrait with Palette (1865) shows some emerald green paint on his palette, squeezed out and ready to paint vegetation such as sunlit grass.

Claude Monet used emerald green among other green pigments and mixtures in his famous Bathers at la Grenouillère, painted in 1869. It has also been found widely in the landscapes of Cézanne, Gauguin, Pissarro and Vincent van Gogh.

By the late nineteenth century, concern over the consequences of using emerald green in household products had risen to the point where the pigment was banned in a succession of countries.

Paul Gauguin’s Arlésiennes (Mistral) (Old Women at Arles) (1888) uses emerald green for the band of bright green grass sweeping up across the painting from the right. It is also mixed for the skin and hair of some of the figures, and in the foliage more generally.

Odilon Redon’s pastel painting of Sîta from about 1893 uses emerald green, chrome yellow and chalk in the prominent yellow-green halo surrounding the woman’s head. Working with soft pastels containing this pigment was particularly hazardous, because of the likelihood of inhaling their dust. At least today we have effective respiratory protection available.

During the twentieth century, genuine emerald green was withdrawn from use as a pigment, although it wasn’t completely discontinued until the 1960s. Since then, paints sold as being emerald green have contained alternatives that are far less toxic.

Emerald green has been found in mixtures used by Paul Cézanne in the patches of vegetation in his huge The Large Bathers (1906). Alongside lead white, vermilion and ultramarine blue, this pigment appears to have been among his most frequently used.

Childe Hassam’s watercolour of White Mountains from Poland Springs from 1917 is one of the last major paintings that appears to have relied on emerald green. Its use in the meadow in the foreground is perhaps the pigment’s last brash farewell.

Reference

Inge Fiedler and Michael Bayard (1997) Artists’ Pigments, vol 3, ed Elisabeth West Fitzhugh, Archetype. ISBN 978 1 904982 76 0.

Here are this weekend’s Mac riddles to entertain you through family time, shopping and recreation.

1: Where to sell an image of the Knolls in a two-year exclusive.

2: Rembrandt, Claude Monet, JMW Turner and Corel.

3: One of the first two, it could be beige acrylic and written by Bill.

To help you cross-check your solutions, or confuse you further, there’s a common factor between them.

I’ll post my solutions first thing on Monday morning.

Please don’t post your solutions as comments here: it spoils it for others.

Before the arrival of Mac OS X, our Macs had remained almost free from the property lists and other XML files that now seem to fill them. Those owe their origin to the grandfather of markup languages, SGML, originally known as Generalised Markup Language. That was invented by Charles Goldfarb, Ed Mosher and Ray Lorie in 1969, when they were working at IBM, as a means of structuring text semantically, and first used a different form of markup, as in
:h1.Chapter 1: Introduction
to set that text as a top-level headline. Ordered lists should look familiar to anyone who writes HTML:
:ol
:li.Item one.
:li.Item two.
:eol.
SGML was flexible as to markup formatting, but has become most widely seen using the angle brackets <> common to HTML, XML, and other markup languages.

Although it has never been popular in its own right, SGML still features in some products where markup is required to impart structure and meaning.

FrameMaker, originally developed by Frame Technology, is a high-end technical publishing system bought by Adobe in 1995. It was then offered in a premium version with extensive support for SGML, seen here in 2002, two years before Adobe dropped this Mac version.

XML

In 1996, a working group of W3C (the World Wide Web Consortium) started developing a profile of SGML that became known as Extended Markup Language, or XML. Work continued through 1997, and in February 1998 XML 1.0 was adopted as a W3C Recommendation. While there’s also a slightly different version 1.1, published in 2004, and various editions of 1.0, in its fundamentals the XML we use today is still version 1.0, with 1.1 only recommended for special purposes.

Property lists

Unlike traditional implementations of Unix, NeXTSTEP used its own property lists to contain serialised objects including settings. When Mac OS X was introduced, those were replaced by a new XML format using a public Document Type Declaration (DTD) still used today.

Although intended to be expressed in plain text, binary representations of XML developed during the early years of the new millennium, and Apple decided to adopt its own, bplist, in the early days of Mac OS X. This brought improved parsing speed, as well as being more compact, and has acted as a deterrent to those who might make casual changes to critical property lists. These were introduced in Mac OS X 10.2 Jaguar in 2002, and have been used as standard for property lists since Mac OS X 10.4. They are described well in this Wikipedia article.

A typical modern property list coded in XML might read
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<array>
<date>2017-10-10T13:13:43Z</date>
</array>
</plist>
That specifies a datestamp in an extended attribute.

Tools

Bundled tools to create and edit property lists have remained disappointingly primitive, but there has been no shortage of contenders from third parties.

This is the ElfData XML Editor, one of the first to be released in 2001, seen two years later in Mac OS X 10.2 Jaguar editing DocBook XML format.

In 2004, David Reitter created a version of GNU Emacs with an Aqua interface and named it Aquamacs. It’s seen here in 2006, in Mac OS X 10.4 Tiger, with its XML tools for editing a property list.

Another early entrant, from 2002, that has blossomed into one of the most extensive and sophisticated XML development environments is cross-platform Oxygen, from SyncRO Soft. Although written in Java its Mac versions have been sensitively implemented. It’s seen here in Mac OS X 10.4 Tiger in 2006, viewing an XML rendition of Shakespeare’s Hamlet.

This is Syntext Serna in 2007, again in Mac OS X 10.4 Tiger, seen editing an XML version of my PhD thesis that had originally been written in Adobe FrameMaker+SGML.

Other editors came and went, such as XML Editor, here in the last few days of Mac OS X 10.4 Tiger in 2007. This is a table from my thesis.

Major text editors also gained XML powers. These are Safari’s preferences in Mac OS X 10.5 Leopard, seen rendered by Rich Siegel’s BBEdit. He first distributed this text editor for System 6 back in 1992, and over 30 years later it remains one of the few high-end text editors for macOS.

My final example returns to the specialist features in Oxygen, seen here in Mac OS X 10.7 Lion in 2012, where it’s being used with a botanical flora.

Today XML and property lists remain at the heart of macOS, something I doubt that Charles Goldfarb ever dreamed of back in 1969.

References

Charles F Goldfarb (1996) The Roots of SGML – A Personal Recollection, Wayback Machine
SGML on Wikipedia
XML on Wikipedia
Property lists on Wikipedia

As we all should really be on holiday, I’m taking a long weekend to look at the stories of three green pigments, starting today with the oldest and most elusive of them, the mineral malachite.

Because green is a secondary colour, it might seem better mixed from blue and yellow, as it has been in various recipes such as Prussian green. But the painter always prefers using single pigments for the purity of their chroma, and the fact that the more pigments that get mixed, the closer the colour comes to muddy grey.

Given the shortage of lightfast bright greens, it’s surprising how little-used malachite green is in European painting, despite its rich colour. For a while it rejoiced quietly under traditional names including chrysocolla, green verditer, and even green bice, but it only ever became popular in Japan and China.

As a natural mineral, malachite is not uncommon, and a reliable source of pure pigment, which is chemically basic carbonate of copper. Malachite green was known to the ancient Egyptians, who appear to have used it as eye-paint. Found abundantly in Japanese and Chinese paintings from the seventh century onwards, it wasn’t used much in Europe until the Renaissance. After that, it almost died out in Europe until the nineteenth century, when it enjoyed a brief revival.

Two versions of the painting by Watanabe Kazan 渡辺崋山 of Sato Issai 佐藤一斎（五十歳）像 show malachite green at its finest.

This version from 1824, now in the Freer in Washington, is known to use malachite green with a slightly blue shade and deep in colour.

This smaller and earlier version from 1821, now in Tokyo, is a lighter, more yellow shade. I’m not aware of its pigment having been analysed, but I’d be surprised if it was straight malachite green.

The biggest problem with its adoption in Europe was the popularity there of oil paint. The pigment worked well where it could be ground quite coarsely and used in water-based media like fresco and egg tempera, but the finer you grind it, the paler it becomes. Oil painters like smooth buttery paints with fine pigment particles, which sadly didn’t work for malachite green.

The rich, almost emerald green robes of Spinello Aretino’s Virgin Enthroned with Angels from about 1380 contain malachite green, here in tempera medium.

Among its earliest appearances in oil paint is this spectacular centre panel of the van Eyck brothers’ Ghent Altarpiece, famous in its own right as the Adoration of the Lamb (c 1425-1432).

Continuing use of egg tempera in the Southern Renaissance helped it survive. Piero della Francesca’s famous The Baptism of Christ (after 1437), made in egg tempera on poplar wood, relies on the pigment for its greens. Microscopic examination of the paint layer here shows coarse mineral particles typical of natural malachite.

In Francesco del Cossa’s Saint Vincent Ferrer from about 1473-75, it has been identified in the dark green grass at the foot of the painting. This too was made using egg tempera.

However, microscopy of this paint layer shows that these pigment particles don’t seem to have been fractured as if they have been ground, but are globular, as occurs when the malachite green has been made by a process of precipitation. Such artificial malachite green didn’t appear in European paintings until after about 1430, just in time for Francesco del Cossa.

Although he painted in oils, Tintoretto was an enthusiastic user of malachite green. To obtain the range of greens seen in the rich and varied colours of vegetation in his Saint George and the Dragon from about 1555, he used this pigment with copper resinate glazes, a technique found in other paintings of the period.

Tintoretto’s vast oil painting of The Last Judgment (1560-62) in the Chiesa della Madonna dell’Orto, Venice, has been found to contain malachite green, I suspect in the band of green depicting the Flood just below the centre. The detail below makes this a bit clearer.

When painting the frescoes formerly in the Villa Aldobrandini between 1616-18, Domenichino and his assistants relied heavily on malachite green. It has been formally identified in this section, showing Apollo pursuing Daphne, where it’s the mainstay colour remaining, and is suspected in most of the others.

Although only classed as moderately permanent, these and other examples of very old frescoes show how well malachite green has retained its colour after four centuries or more. But with the rise of oil painting in European art, it fell from favour.

One of those who participated in its revival in the nineteenth century was Pierre-Auguste Renoir, whose painting of Chrysanthemums from 1881-82 shows how it could still be used in oil paint. But by then there was a much wider choice of more modern green pigments; the revival was short-lived, and malachite green has hardly been used since.

Reference

Rutherford J Gettens and Elisabeth West Fitzhugh (1993) Artists’ Pigments, vol 2, edited by Ashok Roy, Archetype. ISBN 978 1 904982 75 3.