One of the topics of interest within our research project is to examine how Van Gogh modified his approach in the course of making serial paintings that depict the same theme. An example is his series of paintings of The Sower set against a landscape dominated by the bright sphere of a sinking sun. In later versions, the sun came to hover like a halo above the sower’s head, taking on a symbolic significance. It is fascinating to observe how he chose different painterly solutions to render this significant feature in the series of works examined.
To draw the near-circular shapes of the suns Van Gogh could turn to a ready solution, simply tracing around a round object of the appropriate size. He did this either with black drawing material, or with a sharp pointed instrument that scratched through existing paint layers. In the latter case, the painter could have used a compass, but no evidence for this was found in the form of a central point or indentation present in the ground or paint layers.
Painting the sun with yellow provided a naturally light and bright colour, yet Van Gogh varied his method to maximize its luminous effect. Regarding his first attempt of The Sower (Kröller Müller Museum), he wrote to his artist friend Emile Bernard explaining how he had achieved subtle differences in the yellow of the sky and the sun by carefully selecting the shades of chrome yellow used and mixing them with various quantities of white.
Recent portable X-ray fluorescence analysis of the painting conducted by colleagues at RCE, detected significantly higher levels of zinc present in the sun compared to the rest of the sky. This agrees with the artist’s description of using the lightest, lemon shade of chrome yellow 1 (that is zinc, rather than lead chromate yellow) mixed with a little white (probably zinc white) for the sun, compared to mixtures of chrome yellow 1 and 2 in the sky.
…or layer upon layer
Besides mixing the two colours of yellow and white, Van Gogh could overlay them. He did this in his Summer evening near Arles, a landscape that similarly depicts wheat fields against a setting sun and was painted in the month of June 1888. In this case, he first painted a disc of white, apparently bright zinc white, as a luminous base for the yellow applied on top. Slight mingling of the two colours can be seen around the sun’s periphery, where the white underlayer peeps through in places.
An unusual effect was observed in the sun of the large Sower, now in Zürich. Examination of the paint surface with the stereo-microscope revealed tiny, translucent and brightly coloured lumps- apparently dried chips of paint- both pressed and mixed into the yellow paint of the sun. At close viewing these orange, white, green, light blue, red and very dark specks of colour have a jewel-like effect. Might they be deliberate additions by the painter to provide something of a sparkle?
Though this particular technique is unparalleled in works by Van Gogh that we have examined so far, we know that the artist might occasionally add own ingredients to his tube paints on the palette in order to manipulate their properties. An example is his 1887 study of Two dried sunflowers (F 377), where technical investigation has revealed that he added large quantities of white barites powder to his colours as a cheap bulking agent, at the same time enhancing the brushing qualities of his paints. In the case of the Bührle Sower though, we cannot rule out the possibility that the paint inclusions were accidental, perhaps from mixing his yellow colour on a dirty, dried out palette. But then again, Van Gogh was a master in exploiting the coincidental for advantageous effect. So whether these glitters were accidental…?
Thanks to both Jan Jedlicka, Paintings Conservator at the Kunstmuseum in Winterthur and Luuk Struick van der Loeff, Chief Conservator at the Kröller-Müller Museum, for kindly facilitating examining of the paintings in their collections.