Conservation of Allegory on the Equality of all Mankind in Death, a drawing by Jacob de Gheyn the Younger
In the past, this drawing was lined with a sheet of paper because it had many tears and missing areas. When the lining was removed, the central image of a cherub was revealed as a separate drawing, cleverly inserted. Perhaps the artist had changed his mind about what to draw.
The paper, tested and found to be acidic, was treated with an alkaline solution to protect it against further deterioration - this treatment is called deacidification. Tears and creases were repaired on the back with thin, strong tissue, held with wheat starch paste. Small holes and cracks were filled with paper fibres, toned with watercolours to blend in with the drawing.
The paper had a small disfiguring lump of rusting iron in the centre. These are quite common in paper, and usually come from the machines that mix up the paper pulp before a sheet of paper is made. As this piece of iron was near the surface of the paper, it could be removed with the help of a microscope, and the hole filled with paper fibres.
A mount was made using a sandwich of two thin sheets of Perspex with the drawing held at the corners with thin strips of silk. This was then inset into a traditional board mount so both sides could be seen.