As part of a collaboration with Egypt's Ministry of State for Antiquities on projects in the Valley of the Queens and the tomb of Tutankhamen, GCI and Egyptian conservators and scientists have undertaken research on ancient Egyptian plasters. Research began in 2010 to develop treatments to conserve tomb wall paintings at these sites on the West Bank at Luxor. Many tombs that are part of the Theban Necropolis, a World Heritage Site, are in poor condition and require stabilization treatments to secure vulnerable painted plaster.
Modern plasters used to repair Egyptian wall paintings and monuments typically have contained cement and lime. However, these materials do more harm than good at sites such as the Valley of the Queens by contributing to wall paintings deterioration because of their hardness and low water vapor permeability. Compatibility between original materials and new repair is an important conservation principle.
To develop compatible repair materials the team first focused on understanding the composition of the original plasters. Although the general belief is that Egyptian plasters are either gypsum- or earth-based, scientific analysis by GCI and Egyptian personnel tested this belief by studying a wide range of historic plaster samples and locally sourced raw materials. The results were surprising: the plasters were primarily composed of calcium carbonate with clays, sand, and small amounts of anhydrite. The plaster components closely matched a local soil, known in Arabic as hiba, an erosional deposit of the Theban Mountain that surrounds both the Valley of the Queens and the Valley of the Kings. Because of its clay content, hiba can be used as a plaster on its own or with minor modification. This commonly and locally available material was the predominant plaster used in the Valleys of the Queens and Kings and likely was used throughout West Bank sites.
Current research on Egyptian plasters has involved analysis of a wider range of hiba deposits from the area to assess compositional variation. The goal is to relate hiba deposits to the original plasters and to consider their modification by ancient Egyptians. While most historic plasters seem to be composed primarily of hiba, in some cases additional binders may have been added for extra adhesion and workability.
Based on this research, new repair plasters have been formulated, and final research will examine their compatibility and appropriateness compared to original plasters. Depending on test results, the plaster formulations may be modified to better match the properties of the original plasters. Stabilization with the final plaster mixture will be carried out during field campaigns. The GCI also plans workshops for Egyptian and foreign conservators working in the Luxor area in the analysis and characterization of historic plasters and the use of hiba based repair plasters.