Technical studies and conservation of a fragmented painted plaster excavated from the Vigol Sasanian site, Central Iran

Abstract

The study presented here applied various analytical techniques to examine a small fragmented painted gypsum plaster with heart motifs discovered at the Sasanian site of Vigol, Central Iran, to identify the materials used to produce the plaster. The plaster and its paint layer were analysed by X-ray fluorescence, X-ray diffraction, optical microscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy and micro-Raman spectroscopy methods. The results revealed that the plaster layer is made of gypsum with some impurities—mainly soil minerals—with the concentration of these impurities being less at the surface of the plaster. It was also discovered that the heart motifs were painted using minium red lead pigment. As the main damage to the plaster is fragmentation, conservation included joining the fragments and consolidating the surface of the plaster. Finally, a preservation box using transparent polycarbonate plates was designed and manufactured for the display and handling of the newly restored plaster.