Colourants on the Persian architectural decorations from the 11th to the 15th century

Over 200 samples from colourants appeared in 50 monuments in Iran dated back to the 11th century up to the 15th century were identified using micro-X-ray fluorescence (μ-XRF), micro-Raman spectroscopy (μ-Raman), polarized light microscopy (PLM), and scanning electron microscopy–energy dispersive X-ray spectrometry (SEM-EDS). Whereas red ochre, red lead, vermilion, and an organic red dye were identified as red colourants, ultramarine blue, azurite, and indigo were the blue colourants occurred in the wall decorations. In addition, atacamite was the only green pigment identified on the wall paintings and stucco decorations, and carbon black was identified as black pigment. We also show that gold leaf and tin foil have been used in gilding decorations. Furthermore, we were able to discern yellow ochre together with orpiment, natrojarosite, and crocoite in a number of architectural decorations. Moreover, we show that huntite and gypsum are used as white preparation layer of the wall decorations in Iran. Periods of emergence of particular pigments have been discussed and regional preferences in the use of certain pigments are argued. An extensive discussion is provided to compare the colourant appeared on wall decoration with those appeared on illuminated manuscripts in the Persianate world.