This composition has been painted very thickly in gouache, on blue wove paper. The paper makes a modest optical contribution to the pale sky and to the lightest part of the river, in the foreground. In the tiny spaces left between brush-strokes in the foreground, it contributes detail, acting like blue gouache. Elsewhere, the gouache conceals much of the paper colour, but in places it has been scratched out with a pin or other small, sharp tool, for example to create the lighter leaves of the large tree in the centre.
X-radiography of the paper confirmed that much of the gouache contains lead white, which is highly absorbent to X-rays. Lead white is also very opaque in appearance. It was used for the striking white details of the costumes, the distant building, and for the windows of the tower seen against the sky, as well as for the heavier clouds on the left side. 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 medium 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.
X-radiography also indicated that the light yellow pigment used extensively for details in the foreground is chrome yellow, another lead-based material which is easy to characterise without the need to remove even a tiny sample. The chrome yellows had by this time become Turner’s first choice for all shades of yellow from pale through to deep orange tones. This pigment is very opaque in appearance, and almost conceals the blue paper where it was used in the immediate foreground, though it may be mixed with lead white to give it even more solidity. In oil paintings, Turner habitually applied the palest shade over a layer of lead white to make the most use of its clear tone, but he has not applied the same technique anywhere in this watercolour.
Joyce Townsend
March 2011
