Ground layer of paint
Cross-section through the paint showing the ground layer
The thick ground layer of paint consists of two very similar applications of a warm, off-white layer with a thin layer of oil or medium between. The lower layer is denser and paler, the upper layer is warmer and a little more translucent.
In the x-radiograph of the painting (not shown), vertical banding is visible and may correspond to the application of this lead-white based layer or to its smoothing down prior to painting. The prominent network of craquelure in the paint layers originates in this thick ground layer.
In the thinner passages of the painting a gritty white is visible, often more noticeable due to abrasion of the paint layers. In places the heads of these gritty agglomerates have been broken off by the mechanical action of cleaning, as shown in the detail of the reins below. These agglomerates are typical of lead white production in the 18th century.
Detail of the painting showing gritty agglomeration at reins