Why are the plaster sculptures dirty?

Many of Thorvaldsen’s works in the museum are made of plaster. They include the small studies for planned works exhibited in the basement and the original models for sculptures in marble exhibited on the ground floor and first floor.

Some of the plaster surfaces clearly show traces of dust particles and air pollution.

Both the small studies and the original models were originally in clay. When clay dries the shape will change and it will crack. Thorvaldsen therefore had to transform the sculptures into plaster, which is a more stable material, while the clay was still damp. During this process the clay sculptures vanished.

These plaster sculptures are thus the original studies and models for Thorvaldsen’s sculptures in marble, the first versions so to speak, of the work, whereas the marble sculptures were often carved in several copies.

Ever since Thorvaldsens’s time air pollution and smoke from the stoves in his studio in Rome and in the museum have fallen on the originally white plaster and penetrated deeply into the porous surface. On some sculptures the dirt is causing the spectator great inconvenience.

It is now possible to clean the works chemically. Often the museum will, however, only clean to a very limited extent because: the surface of the sculptures may be damaged, measuring marks etc. from Thorvaldsen’s time may disappear, the surface of the plaster sculptures may become dim and dull. Finally, the reappearance of the completely white plaster may make it more difficult for the spectator to experience the shape of the sculpture.