Purple Fluorite: A Little Known Artists' Pigment and its Use in Late Gothic and Early Renaissance Painting in Northern Europe

Abstract

A purple calcium fluoride, CaF2 (fluorite), a natural inorganic pigment, has been identified on a small number of painted artworks from c. 1450 to 1520. It was used on panel paintings, polychrome wooden sculptures, wall paintings and architectural polychromy from Southern Germany, Tyrol (Austria), Switzerland, Silesia (Poland) and Hungary. Fluorite was identified as an artists' pigment in 1968, but this case was first published in 1986. An intensely blackish-purple type of fluorite called antozonite (German: Stinkspat) was probably used for this pigment. Paint layer reconstructions of some of the paintings where fluorite was identified clearly illustrated its function and characteristics together with various pigments and binding media. Due to its poor tinting and hiding power, it was often used to enhance a colour effect in a pigment mixture. It was also used in combination with lead white to obtain a purple colour. Fluorite can only be identified with certain analytical methods, the most important being microchemical analysis, polarized light microscopy (PLM), and X-ray diffractometry (XRD). Further analysis with total reflection X-ray fluorescence analysis (TRXFA) can be applied to identify trace elements and possibly the sources of this pigment.