Technological Study of Gilded Mina i Ware Based on Microscopic Investigation and Historical Documents

In medieval Islamic Iran, mina was known as a general term for enameling metal, glass and ceramic. Consequently, in modern times Mina’i is one of the most important types of Islamic ceramic production and identified by stone paste body and multicolored polychrome over-glazes which represent figural, geometric and floral designs as well as calligraphic perform. Additionally, Mina’i wares are in some cases enlightened as gilded surface. The style can be found in numerous forms that include bowls, ewers, cups, beakers, jugs, inkstands and tiles. They are often referred to as “Haft-Rang” (seven-color) ceramics due to their polychromic character. The colors were red, brown, cobalt blue, green, black, white and gold. It was believed, until quite recently, that one of these seven colors, namely cobalt blue, was painted not over, but in the glaze, and all the others were painted over. These often finely painted wares are believed to have originated in Seljuq Iran during the late twelfth to the early thirteenth century, but there are no contemporary accounts of their production. Little is known about the manufacturing process of Minai ware, because no contemporary literature has yet been found. The earliest literature that mentions Minai ware is Abu’l Qasim Kashani’s Treatise on ceramics, which was written in 1301 or earlier, and the technique for Minai multicolored enamels (called ‘seven-colored’ in the literature) had already been lost Potters in Iran (Persia) began to produce a special type of pottery, that was decorated with multicolored enamels over an opaque white or turquoise base glaze as well as painted applications of blue, turquoise, black, red, pink, purple, white, brown, and green glaze in or over base glaze. Mina’i wares are in some cases enlightened with gold flake surface and applied relief. When Abu¯’l Qasim wrote his treatise on ceramics in 1301, the technology of Minai wares had been lost but gilding technology on the other types of ceramic such as lajajvardina and tiles was continued. The main production site for Minai ware is believed to be Kashan in Iran, which was the main ceramic production center at that time, and several pigment sources are also found there. Besides Kashan, Sava, Rayy and Natanz are also believed to have been production sites, although the vessels still cannot be related to these sites individually. Recent excavations in Alamut Castle caused to discovery of many complete Mina’i wares and sherds. In this research, 7 Mina’i sherds that excavated from Rayy and Alamut castle were analyzed with optical microscopy and chemical composition analysis, were measured using scanning electron microscopy and micro PIXE to characterize and identify the process and composition of gilded Mina’i wares. This paper focuses on defining the elemental composition of gold findings in order to identify gilding process and the gold/ceramic adhesion mechanism. Scanning electron microscopy (SEM) observations showed that pure gold leaves were directly fired on a substrate glaze. In addition, a red ochre and black pacified glazed line surrounded over and under the gilded areas. Although the presence of gold layer under heated the red ochre pacified drawing lines shows thermal process on the gold leaf but over red or black accent drawing glaze, in some parts, demonstrated that the gold leaf was applied after drawing the red lines and maybe after firing, there was no evidence to show these lines had been fired either in the same time with other over glaze decorations or later. The results support that gilding decoration was using both mechanical as well as thermal process for adhesion mechanisms between gold leaf and its substrate. All the results of this research confirm Abulaqasim’s writings concerning gilding process.