Investigating the Technology and Conservation and Restoration of the Mosaic Tile Decorative Mosaic Tiles of Musalla Historical Building in Mashhad

The Mosalla of Paein Khiaban of Mashhad is one of the largest and most beautiful historic mosallas in Iran, built at the order of King Suleiman I during the Safavid era. according to inscription on the tile of the central porch, the date of construction and completion of the building is 1087 A.H. The architectural structure of the building consists of a high central porch in the middle and two domed porticoes on the sides. Both the internal and external surfaces of the building are decorated with various architectural elements, such as stucco work, tile work, painting and muqarnas. Among the various decorative employed in this structure, the mosaic tiles of the mihrab are unparalleled in terms of beauty and sophistication. Laboratory analysis of the chemical composition of the glaze of the altar tiles using SEM-EDX method demonstrated strong agreement with findings from other researchers, indicating a continuity of the tile-making tradition and glaze production with similar technology throughout the Safavid era across various r regions of Iran. A petrological study of the mineral composition of the body of the tiles also revealed the use of a similar and appropriate mineralogical composition, paired with good firing in their production, which contributed to the strength and durability of the tiles. The pathology of the building and its decorations indicated that a combination of different physical, chemical and human factors caused the destruction and erosion of the structure and its decorations, including the mosaic tiles. Among these, human activities and irregular urban development surrounding the building, along withimproper and careless restorations, played the main role in the destruction and erosion of the tiles. Considering the importance and sophistication of the mosaic tiles of the altar, following laboratory studies, the tiles of this part of the building were conserved and restored. For this purpose, after the primary conservation measures through cleaning and consolidation, the missing parts were restored according to the principles and theoretical foundations of restoration in the method of complementary restoration through color-matching.