Consolidating clay coffins
Coffins made of fired clay were used all through ancient Egyptian history. These coffin lids are particularly interesting because the clay comes from Dakhla Oasis. Because it is quite a coarse material, and because the temperature at which they were fired was rather low, they are now very fragile.
The conservator responsible for consolidating them is Deborah Walton. The first task is to strengthen the basic fabric of the coffins, which she does by applying a very weak concentration of an acrylic resin in a solvent.
The broken pieces of this coffin were probably put back together in the early 20th century, using shellac (a natural resin, produced by an insect). It is very thick and was probably applied hot, because it now has a deep brown colour. Some of these old joins have failed, and Deborah has to clean the shellac off the edges. She does this by first softening it with industrial methylated spirit and then lifting it away from the surface using a scalpel and cotton wool swabs.
She now needs to work on the back, but the face is too fragile for us simply to turn it over. The solution is to use a smaller version of the medical vacuum cushion, which we used in moving the Roman mummy. The bag is placed over the top of the face and gently moulded to fit exactly around the head. Deborah pumps out the air to make the shape hold securely and puts a board on top. The whole group can now be turned over, with the cushion giving complete support for the fron whilst the back is cleaned and consolidated.
After the pieces have been stuck together, the back is made stronger by filling in the gaps with a past made up of an acylic resin, with glass microballoons and cellulose powder to make it more bulky. Before the gaps are filled, a layer of Japanese tissue is put on the edges so that the paste sticks well, but can still be removed later if necessary.