Conservation departments
X-ray of the painting
While a simple visual examination of the back of the painting reveals quite a lot of information, to get the full picture you need to use x-radiography to look beneath the surface.
The x-radiograph, or x-ray, above shows all the features of the panel and its construction, from the cross batons and large nails heads to the individual cracks in the paint. The outline of the painted figure is also just visible.
The fibres that show up in the x-ray follow a completely different pattern to those seen on the back, indicating that they are on the surface not the back of the panel. A magnified detail of the x-ray is shown below.
We also know from Spanish artists’ treatises that glueing fibres to the panel, front and back, before starting the painting was common practice in the 15th and 16th centuries.
Details showing sacking tacked to the side of panel on the left
and a magnified view of the fibres on the right
A type of coarse sacking is tacked along both vertical sides of the panel and continues under the paint layer. From the x-ray we can see it does not extend under the whole painting but is in strips along each vertical edge.
From examination of the painted surface it is clear that there is little or no original paint along either side and the canvas is part of an extensive repair, probably necessitated because the edges of the original painting were damaged.