Gaji, a Gypsum-Earth Plaster in the Wall Painting Technology of the Church of St. Demetrios of Thessaloniki, David Gareji, Kakheti, Georgia

Gaji is the Georgian name both for a gypsum-and-clay-containing soft rock found in eastern Georgia, and for the plaster traditionally derived from it. Gypsum-earth plasters have a long history of use across Caucasia, central Asia, and the Middle East. Gaji has been used in the preparation of mortars, plasters and decorative finishes, and as a support for Georgian religious and secular wall paintings together spanning the 9th – 20th centuries. Little research has been conducted into its properties, however, and within the context of wall painting conservation neither its influence on condition nor its implications for treatment have been adequately explored. Using the Church of St. Demetrios of Thessaloniki, rediscovered in 2015, at the monastic complex of David Gareji as an example, this paper explores the use of gaji plaster technology and the conservation challenges it presents.