Timurid, Ottoman, Safavid and Qajar Ceramics: Raman and composition classification of the different types of glaze and pigments

Abstract

Raw materials significantly determine the final composition and properties of a fired ceramic. Raman analysis which characterizes micro- and nanostructures of (coloured) glazes, opacified or not, was applied to shards mostly collected before the 1960s, currently at the Louvre Museum, originated in Anatolia, the Caucasus, Iran and Central Asia, which are, for most of them, characterized by the use of black lines to separate coloured areas, and dated to the period between the 12th and 19th centuries. Measurements were carried out in the laboratory with a blue laser excitation and/or on the conservation site with a mobile device (green laser). Three types of glazes were identified by their nanostructure of the silicate network: (i) a lead-rich glaze analogous to that of Byzantine, Zirid to Hafsid and al-Andalus productions, (ii) a lead-alkali glaze typical of the Ottoman productions of Iznik-Kutahya, and (iii) a mixed (poor lead/lead-free)-alkali glaze typical of Safavid productions. The colour determines the precise composition of the glaze. The identification is not only based on the signature of the stretching mode of the SiO4 tetrahedron (position of the wavenumber of the component(s)) but also on the position and shape of the continuous luminescence of the Raman background, characteristic of the raw materials used. Lead-tin yellow, Fe-rich, Mn-rich and Cr-rich black pigments and opacifiers made of cassiterite and wollastonite were also identified. The results (type of glaze and deduced processing temperature) were discussed in the light of the ternary phase diagrams visualizing elemental composition determined in previous works and the microstructure examination on the polished section (defining single or multistep firing cycles). Continuity was highlighted on the one hand between the tiles of Bursa, Edirne and Istanbul (Ottoman Iznik-like production) and on the other hand between those of Samarkand area (Timurid) and Iran. The procedure was then applied in the study of three objects (two dishes and a bowl) which are very representative of the productions of the Turkish-Persian cultural areas: a polychrome mina'i cup with decoration representing a rider, an Ottoman Iznik fritware with polychrome floral decoration, and a blue-and-white Safavid ceramic with a decoration representing a shrub.