Centro Cultural Palacio la Moneda (Santiago, Chile): Turner Watercolours
Technique and condition
In this composition, the paper was given a grey wash, and opaque white gouache mixed with many colours was applied everywhere, to give an appearance almost like oil paint. This conceals the colour of the paper, which is quite likely to be white. The arch has been moved farther to the left, and coloured.
A number of warm-toned and yellow/brown earth colours were used, and the terracotta and buff shades may include Indian yellow, a pigment which Turner used in watercolour occasionally in earlier years, but more rarely by this time. It is recognisable by its golden glow when the sheet is examined in ultraviolet light. The bright blue of the sky could only be achieved with an intense blue pigment such as Prussian blue. The other possibility of cobalt blue can be discounted, because it would have been recognisable in ultraviolet light had it been present.
An X-radiograph was made of the whole sheet, to investigate the gouache. This indicated that for the buildings, cows and people it was made from lead white, not chalk as used by most watercolour artists at this time. Lead white is the very opaque pigment that Turner and all his contemporaries used in oil paint, and he frequently used the full range of pigments that he employed in oil paint, ground in gum water for application to paper. Lead white is so dense that it absorbs X-rays completely, so an X-radiograph of either a painting or a watercolour can reveal the patterns of its use, and can also reveal areas where the artist altered the composition without scraping off the earlier paint completely. That is the reason that a change in the position of the arch is known here, and also the reason that it can be stated confidently that Turner frequently used lead white in gouache, and thereby established a trend which later watercolour artists would follow. The dense gouache is particularly effective when contrasted with the bright blue sky here, and Turner used it regularly for white highlights and sometimes for extensive and key parts of the composition, to achieve a visually similar effect on blue paper for both studies and finished watercolours.