This weekend we’re visiting what used to be a small village on the bank of the River Oise, where several of the French Impressionists developed their skills in painting landscapes en plein air. In yesterday’s first article we had reached 1876, the year of the second Impressionist Exhibition in Paris.

In complete contrast to his few landscapes influenced by Paul Cézanne, in 1876 Pissarro also painted some views of the commercial barges trading on the River Oise, including this of Barges at Pontoise, the only canvas in which the boats dominate his composition. This painting remained unsold at the time of the artist’s death, and wasn’t even exhibited until 1936.

The Oise near Pontoise in Grey Weather is another of Pissarro’s views of the River Oise from 1876.

The Rainbow, Pontoise, which Pissarro painted in 1877, was shown at the Third Impressionist Exhibition that year. It’s a panoramic view of the fields around the neighbouring area of Épluches viewed from Pontoise, with a modest and realistic rainbow.

Around 1877, when Pissarro was probably in company with Paul Cézanne at Pontoise, the pair of them painted the same motif hidden or revealed by the same trees. Pissarro’s version of Côte des Bœufs, Pontoise, above, is the more famous, and captures texture in everything, from the smoother surface of the track to the smaller branches, and presents an essay on the form and structure of trunks and branches.

Cézanne’s La Côte Saint-Denis à Pontoise shows little or no anatomical basis to the construction of his trees, whose branches are only loosely related to foliage. He simplifies throughout, with little or no texture, and more basic shadows, on the trunks, and the foliage is depicted as amorphous areas of leaf colour.

Béliard’s Moulin de Chauffour, Effect of Snow (1878) is another winter scene from the area near Pontoise, and is significantly less painterly than Pissarro or Cézanne.

By 1880, when Pissarro painted this Landscape at Le Valhermeil, Auvers-sur-Oise, his work was losing its conventional Impressionist facture, as he adopted smaller, staccato brushstrokes and his style became more ‘pointillist’.

Pissarro also started to transfer his attention from the land to its inhabitants, here the rural poor of these Cottages at Le Valhermeil, Auvers-sur-Oise (1880).

Pissarro’s Peasant Woman Digging, the Jardin de Maubuisson, Pontoise (1881) shows two women working in the vegetable garden of this large house in the village. This painting was first shown at the seventh Impressionist Exhibition the following year.

The Harvest, Pontoise, from 1881, is one of several of Pissarro’s paintings focussing more closely on agricultural activities, and now becoming overtly ‘pointillist’. Because of the brushwork involved, he couldn’t have painted this in front of the motif, and it turns out to be a second copy of an earlier and apparently identical painting.

This increasingly human content, in paintings such as his Peasant Woman and Child Returning from the Fields, Auvers-sur-Oise from 1881, drew comparisons with Millet, from whom Pissarro sought to distance himself in terms of modernity. This painting was bought by Durand-Ruel later that year, and shown at the seventh Impressionist Exhibition.

Pissarro later concentrated his attention on Éragny, then cityscapes of Paris. Cézanne returned to his family home in Aix-en-Provence, and Béliard became the mayor of Étampes further south. Today Pontoise is part of the ‘new town’ of Cergy-Pontoise, and its population has grown to well over 30,000, within an urban area of nearly a quarter of a million.

This weekend we travel to what used to be a small village of around six thousand on the bank of the River Oise, to the north-west of Paris. Pontoise was the centre of early Impressionist landscape painting in front of the motif, and appears in hundreds of works painted there from the late 1860s. It’s where Camille Pissarro lived and developed his skills, Paul Cézanne learned to paint en plein air, and others including Vincent van Gogh and Charles Daubigny painted.

The country around Pontoise has also been painted extensively. In these two articles, I include some from Auvers-sur-Oise, a little upstream, but exclude those from Ennery to the south, Éragny down river, where Pissarro settled later, and Osny to the north-west, all names you’ll see in the titles of significant Impressionist paintings.

We start in 1867, in the early days of the development of Impressionism, with Camille Pissarro’s Côte de Jalais, Pontoise. This realist view shows the hill of Les Jalais at l’Hermitage, where Pissarro lived at the time, viewed from the Chemin des Mathurins in Pontoise.

The year after he painted these Apple Trees at Pontoise, the House of Père Gallien (1868), the Pissarro family moved to Louveciennes, also to the north-west of Paris, where they intended to settle down in a large rented house. It was here that Pissarro first got to know Alfred Sisley well, when they painted in company, and alongside Monet and Renoir, all four of them starving and fighting off despair from their lack of sales.

The forgotten Impressionist Édouard Béliard may well have painted Boulevard de Fossés in Pontoise alongside Pissarro, Cézanne and Guillaumin in 1872.

Béliard’s Pontoise, View of the Lock (1872-5) was probably among his paintings shown at the first Impressionist Exhibition in 1874. Its composition is reminiscent of Sisley’s The Canal Saint-Martin, Paris from 1872, and its style is similar to those of Pissarro and Sisley at that time.

Paul Cézanne started learning to paint en plein air alongside Pissarro’s easel in 1873, when he painted this view of the House of Père Lacroix, Auvers-sur-Oise. As with all beginners, he took a long time getting the painting to look right, so different sections of the roof were painted several hours apart, as reflected in the orientation of the shadows here.

This view from Cézanne’s first campaign along the River Oise shows the northern bank near the hamlet of Valhermeil, slightly up-river from Pontoise.

Of all the paintings shown at the first Impressionist Exhibition in Paris in 1874, Cézanne’s The Hanged Man’s House, Auvers-sur-Oise (1874) was among the most successful, as he sold it to the collector Count Doria for three hundred francs.

Béliard’s Pothuis Quay in Pontoise, Effect of Snow from 1875 may have been exhibited at the second Impressionist Exhibition in 1876, and is similar in subject and style to the winter scenes painted around Louveciennes by Pissarro and Sisley from 1870 onwards.

In February 1875, with snow still falling, the Pissarros returned to their house in Pontoise, for Camille to paint there again. Effect of Snow at L’Hermitage, Pontoise (1875) strikes a fine balance between an impression captured in haste, and sufficient detail to make it more than just a passing moment.

That year a few of Pissarro’s paintings appear to have been influenced by Cézanne. Perhaps the best example is The Small Bridge, Pontoise, which could easily be mistaken for one of Cézanne’s views in the woods of northern France.

View of the Côte des Gratte-Coqs, Pontoise from the same year is also less distinctively one of Pissarro’s works.

In 1876, Pissarro painted this large view of one of the gardens in Pontoise: The Garden of Les Mathurins at Pontoise, belonging to the Deraismes Sisters. In fact, the sisters were only renting this large and impressive property, just down the road from where the Pissarros lived, in the Hermitage district of Pontoise. It had formerly been a convent until the French Revolution.

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.