Joseph Mallord William Turner

This study was executed on white wove paper. Sketchy and light pencil under-drawing is evident. The composition is made from brightly-coloured washes which heavily overlap, while light areas in the composition were left blank or have only been very lightly coloured. Some have hard edges because they were applied to dry paper, and others are very diffuse in appearance because the paper was wet. Some of the latter were applied late in the sketching process, in a reversal of Turner’s common practice of soaking the paper first, although their sequence may reflect only the rapidity of the painting process. Some paint has been worked with the artist's fingers, a technique he used regularly in both watercolour and oil medium. The surface is very glossy in places, which suggests the presence of additional gum water, locally applied.

Examination at moderate magnification, up to x40, made it clear that many of the washes were premixed. The identifications of Prussian blue were in fact confirmed by removing a tiny sample the size of a pin-point, and placing it in the sample chamber of a scanning electron microscope, under an X-ray beam. This beam interacts with the elements that make up each pigment, and the resulting spectrum makes it possible to work out which elements are present. If it is already known that the wash contains only one pigment, it is then possible to work out exactly which was used. Visual identifications of these materials – as was done here for vermilion – can then be made on other watercolours, when it is already known from examination at moderate magnification that the wash consists of a pure pigment and not a mixture. In a complex and finished watercolour with multiple overlying washes, it would be foolish to attempt such visual identification.

At this date, Turner experimented with a number of studies using blue, red and yellow. Here he used Prussian blue, which has a clearer, brighter tone than the traditional indigo, vermilion, red lake, and possibly even chrome yellow. This had been patented in 1814 and used by Turner in oil in the same year in Dido and Aeneas (Tate N00494). Its use here would be very early in watercolour, but it was not justifiable to sample from such thin colour washes, to investigate it further. In later decades, Turner would use this pigment extensively, often in colour studies made in blue, red and yellow.