This chapter provides a description of colour changes in the Amsterdam Sunflowers due to chemical alteration of pigments, with a focus on geranium lakes and chrome yellows.
The brilliant and forceful colours of these and other late nineteenth-century synthetic materials offered artists such as Vincent van Gogh new means of artistic expression that exploited a range of contrasting hues and tints. However, geranium lakes have a strong tendency to fade and chrome yellows to darken under the influence of light. Van Gogh, like other artists of his day, was aware of this drawback, yet he continued to favour the use of both pigments up until his death in July 1890 due to the unparalleled effects they gave. In April 1888, Vincent wrote to his brother Theo:
You were right to tell Tasset that the geranium lake should be included after all, he sent it, I’ve just checked – all the colours that Impressionism has made fashionable are unstable, all the more reason boldly to use them too raw, time will only soften them too much. So the whole order I made up, in other words the 3 chromes (the orange, the yellow, the lemon), the Prussian blue, the emerald, the madder lakes, the Veronese green, the orange lead, all of that is hardly found in the Dutch palette, Maris, Mauve and Israëls. But it's found in that of Delacroix, who had a passion for the two colours most disapproved of, and for the best of reasons, lemon and Prussian blue. All the same, I think he did superb things with them, blues and lemon yellows.
Van Gogh's use of unstable colours opens a series of questions regarding the extent to which colour change affects the way his paintings look today, as discussed here in relation to the Amsterdam Sunflowers. Furthermore, given the frequency with which geranium lakes and chrome yellows occur in Van Gogh's paintings of the period 1888–90 and the predominance of chrome yellows in Sunflowers, it becomes important to understand the factors that can drive these processes of deterioration in order to develop appropriate strategies for conserving the artist's works.