The Gallery’s painting Christ Driving the Traders from the Temple from after 1569.
By means of X-rays the conservators can spot damage to a painting. Such damage is not always visible to the naked eye. For example, X-rays can show if there are wormholes in a painting.
X-rays are very short electromagnetic waves capable of penetrating many different materials except materials that contain heavy metals such as lead. If, for example, the painting’s ground contains flake white (lead white) the X-rays cannot penetrate that particular layer. The ground is the first layer of pigment applied to the wood in order to create an even surface for painting on. Today such grounds will typically be applied to a canvas, but in the 16th century artists often painted on wood rather than canvases.
Flake white in the colour layer
In the 16th century it was also common practice for artists to use flake white to create white colour layers. Indeed, the Gallery’s painting contains flake white, but this is located in the colour layer rather than in the ground. This means that the conservators were unable to see through those parts of the colour layer where flake white has been applied. The X-ray image of the painting shows you where flake white has been used; it shows up as white spots in the X-ray image.
The squares visible in the X-ray image are pieces of wood that have been applied to the back of the painting at some point in the past in order to prevent the painting’s base from coming apart. The pieces of wood make sure that the back of the painting does not collapse even though the wooden panel is riddled with wormholes. The X-ray images make it possible to see the extent to which the worms have hollowed out the original wood.
In some cases it will be necessary to fully replace the wood, but here the conservators only needed to replace selected pieces of wood.
How did artists work with materials in the 16th century?
The X-ray images gave the conservators important information about the composition of the planks that make up the wooden panel. In this way the conservators could determine how artists worked with their materials in the 16th century.
Damage becomes visible in X-ray images
The X-ray image shows a horizontal white line towards the bottom of the painting. It represents hidden damage that the conservators discovered as a result of the X-ray session. In fact, the damage had already been repaired, and to the naked eye the painting looked well restored. However, when the conservators cleaned the painting they found out that the colours used to repair the damage had aged differently from the original colours. So the conservators had to remove the old repairs and repair the damage again.