Using Spectroscopic and Microscopic Methods in the Study of the Identification Characteristics of Paint Materials Produced Based on Traditional Persian Recipes: Cinnabar Red

Cinnabar was one of the most common red pigments throughout history and was obtained naturally and artificially. Considering this pigment's importance and wide application in Persian artworks, this research will attempt to study the identification characteristics of natural and artificial cinnabar by microscopic and spectroscopic methods. Therefore, the research tries to answer the question, what are the identifying characteristics of the cinnabar resulting from its making methods in old Persian recipes? Natural cinnabar was prepared from the historical bazaar of Tabriz, and artificial kind was made based on different old Persian recipes from the 12th to the 19th centuries. After applying the necessary processes on samples, including acid washing with pomegranate juice and lemon juice, the identification characteristics of the pigment in pure form and combination with gum and animal glue binders were investigated using a polarized light microscope, Raman spectroscopy, SEM-EDX, and reflective spectrophotometer. The results show that despite the difficulty of separating artificial and natural cinnabar with a light microscope, they separate by SEM images based on their morphology differences. Also, EDX analysis makes it possible to identify them according to the ratio of sulfur to mercury due to impurities in natural cinnabar. Analysis of the Raman spectrum with an emphasis on the 253 cm-1 band can be an important indicator for identifying cinnabar pigments without interfering with binding effects. However, the distinction between natural and synthetic pigments requires statistical analysis.