Wednesday, May 20, 2009


Researchers found that at least three major previous conservation treatments were inside the chapel. In 1913, Ernest MacKay replaced a number of plaster fragments and fittled the ceiling with three light iron girders.

In 1914-1915 shows the plaster fragments set into the black muna (bottom pic from Griffith Institute, Ashmolean Museum, Oxford). The top photo from 1966 shows the white repair plaster over the muna substrate to stabilize the fragments. In the 1980s/90s, polyvinyl acetate (a synthetic binder) was mixed with sand and clay to form a mortar in the existing white plaster areas. B72 (Paraloid) was also introduced to stabilize the paintings.

Over the years, the plaster and pinkish PVA had cracked becoming unstable and visually distracting. The previous fills also resulted in the creation of 'haloes' or yellow tidemarks around the losses. Samples of sand and sandstone powders were analyzed to see if they would produce adverse chemical changes in the lime plaster or with the original black muna plaster. After testing and examination with polarized light microscopy they were found safe to use. The colours of different sands were tested and a mixture of lime putty, local sandstone powder, light building sand and a local pinkish sandstone were decided on. The top photo shows the previous repairs being removed.

The loose materials of the fill have to be removed and the surface wetted with a brush to aid adhesion and to slow the drying rate. The sand and limestone putty mixture had to be applied quickly, taking care to avoid contact with the original edges.

The repairs were then cut back under light to ensure an even surface and that the mortar followed the plane of the wall. Then mortar was pushed into the edges of the original plaster to ensure good contact and mimic the original plaster surface.

It could be that in another 40 or 50 years or even less, these repairs will be removed to make way for a better conservation project. It's certain not to last the 3 thousand years the paintings have. All this stuff is probably copyright but sueing me will do you no good but since thousands read this blog, I won't charge you for the publicity.

No comments: