Structural study of pigments on Stucco inscription on the porch of Seyyed Shams-din tomb (Yazd-Iran)

Gypsum is one of the traditional materials in Iran that has been used extensively in historical periods, especially in hot and dry climates, in architecture and architectural decorations. In the Islamic era the peak of the gypsum stucco decoration is in 13 and 14 centuries AD. Color was used on stucco decoration to express the artistical and aesthetical effect of this art. Tomb of Seyyed Shams-din is one of the famous monument of the 14 century in Yazd. In the porch of the building, a stucco inscription in Kufic script has been executed in the form of mother and child. The background of this inscription has been executed with abstract plant motifs such as Arabesque. Blue, red and green colors have been used in the background of the inscription. Usually, in order to improve the quality of the paint layer, the primary layer was first applied on the plaster. Due to the passing of the time, only a small part of these colors remain. The conservation of the remnants of the art of the 14 century requires an accurate technical knowledge of the work. In this regard, the study of the structure of the pigments on the stucco inscription in porch seems necessary. Therefore, the present study tries to use examination and scientific studies to accurately identify the pigments used on the stucco inscription of the porch and also the golden layer on the molded gypsum arrays on the moqarnas of the arc in front of the porch in Seyyed Shams-din tomb. The results show that the blue pigment used in the stucco inscription is an Azurite; Red is a Vermilion; Green is a malachite; filler or pigment of primary layer is Huntite, and the gold layer on the molded gypsum arrays is a Tin leaf with a resin or oil coating.