Joseph Mallord William Turner

This study has been painted using several premixed colours of gouache on blue paper, often combined on the paper with rapid brush-strokes. The gouache was applied thickly, and even as a single layer it cancels the optical contribution of the paper in most of the image except the middle ground, where the paper ‘reads’ as another area of light blue.

X-radiography of the sheet was used to trace patterns of use of lead-containing paint in this study. It indicates that the white pigment in the gouache is lead white, which accounts for its extremely opaque surface appearance. Turner was an early user of lead white in gouache, and by the middle of the nineteenth century other artists were also using it regularly. Lead white in scanty amounts of gum water as Turner used it, can easily discolour to a speckled or solid dark brown when it reacts with hydrogen sulphide gas, a common urban pollutant during the nineteenth century. Here, the gouache is in excellent condition. The yellow pigment does not show up in the X-radiograph, which indicates that it is not chrome yellow (whose chemical formula is lead chromate) despite its colour. Probably it is yellow ochre.

The study could have been done very rapidly, and the trees were painted over the sky after it was completed.