Research at the Hamilton Kerr Institute
Jan van Os
Reconstruction of a Dutch flower painting
The reconstruction of van Os' Still Life
executed by Dr Spike Bucklow and illustrating the artists' techniques
The painting is signed J. Van Os fecit on the stone ledge beneath the bunch of grapes. Jan van Os (1744-1808) became the Director of the Academy at The Hague and is known to have exhibited twelve paintings - mostly flower pieces - at the Society of Artists in London between 1773 and 1791. The painting was given to the Fitzwilliam Museum as part of the Broughton Collection in 1973.
The painting was copied as part of the final year of the Institute's three-year post-graduate course in the Conservation of Easel Paintings. The intention was to reconstruct the artists' methods rather than the finished appearance of the painting and evidence of all stages of production was therefore left visible.
The original is painted on a single piece of mahogany (787mm by 587mm) with the grain running vertically. The panel is 10mm thick with a 30mm bevel to 5mm at the edge.
When the painting was reconstructed in the 1990s it proved impossible to find a piece of mahogany of the same quality. The copy was therefore made - to the same dimensions as the original - from two mahogany boards, joined with animal glue. Joining boards with animal glue was an established practice.
The panel was smoothed and prepared with size (dilute animal glue) and three layers of chalk in animal glue. When dry, the brushstrokes were removed by sanding to give a ground layer with a thickness of less than 0.5mm. Equal volumes of lead white and chalk were then ground in cold-pressed linseed oil and two layers (thinned with oil and turpentine) were applied across the whole of the ground.
The original underdrawing was necessary because not all the flowers and fruit were available at the same time. Jan van Os planned the composition in pencil and painted each element as it became available. Some fruit and flowers would have been painted from life, and others would have been copied from studies. The drawing is very detailed and was followed quite faithfully in the paint layers. No signs of mechanical transfer - pouncing, stencilling, etc. - were evident and there were no geometric construction lines.
The paint layers
a detail from the original;
showing underdrawing visible through the paint, around the edge of some of the grapes
Following the pencil underdrawing, broad areas of the painting were blocked-out in pale oil paint. These flat areas of colour provided an approximate context for those elements that were to be painted first. Each type of fruit or flower was painted in a technique that suited its visual characteristics, indicating that the painting was an assured product of an experienced painter.
Some passages, like the roses, were painted in a single layer, and needed very little preparatory work or finishing. However, in most passages, like the white grapes, the initial pale blocked-out layer contributed to the final effect. This first layer was more or less covered with a modulated layer of varying thickness and of approximately the same hue. This layer was then glazed with darker paint (for shadows) or scumbled with lighter paint (for bloom) and finished with discrete white highlights (for reflections). Jan van Os' formulaic approach also accommodated the lighting of individual elements. For example, the black grapes in shadow were painted directly over a light violet block of colour, but illuminated black grapes had an underlayer of bright opaque red that was allowed to shine through subsequent layers of transparent red, blue and black.
The pigments were typical of late eighteenth-century painting. Chalk and lead white have already been mentioned as colourless or white pigments. These were used separately (chalk in the ground, lead white in the highlights), mixed together (in the imprimatura layer) and were also each mixed with other pigments to create the generally high-key palette. Mixtures containing chalk tended to be used for transparent layers, and mixtures containing lead white were for light-tone opaque layers.
Natural pigments included yellow, red and green earths. More highly refined natural pigments included animal products like the insect-based cochineal and kermes, plant products like yellow lakes and indigo, and mineral products like ultramarine blue. Synthetic pigments included colourless alum (which carried the lake dyestuffs) vermilion, red lead, lead-tin yellow and Prussian blue. Only the last of these was a relatively recent addition to the artists' palette.
The paint was composed of poppy oil. This dries much slower than linseed oil, but tends to discolour less with age. The high tonality of Jan van Os' flower paintings would have been particularly susceptible to yellowing medium and he was evidently prepared to work slowly in order to gain the advantage of poppy oil's long-term stability.
Not all of the painting had the same medium. We have seen that the ground had a glue medium, and that the imprimatura was made with linseed oil. The white and red striped tulip had a mixed medium - it was an emulsion made from oil plus and aqueous medium. Jan van Os created the thixotropic emulsion so that he could build an impasto paint surface specifically for the white petals. The petals seem to have every rib laboriously painted but close inspection shows that these petal-ribs are shadows cast by textured paint, and what appears to have been hours of effort was probably executed in just a handful of deft strokes with a stiff brush and a mayonnaise-like paint.
Such masterful use of surface texture is difficult to see when paintings are viewed in the diffuse light of a museum or gallery, but it would have been very obvious when the painting was displayed in a relatively dark room with a small window. The image below shows how the appearance of the painting changes with angular light. If you have a Java enabled browser you will see an animation of the tulip detail, lit from varying directions. You can left click and drag the mouse over the image in order to move the lightsource around.