New evidence for the intentional use of calomel as a white pigment

In this work, we report the results of the in situ application of micro-Raman spectroscopy to the analysis of two historic painted objects: a 15th-century illuminated manuscript and a late 16th-century portrait miniature. Both objects were unexpectedly found to contain calomel (Hg2Cl2), intentionally used as a white pigment. Calomel was a widespread and popular medicine until it fell out of use at the end of the 19th century due to its toxicity, and a material called 'mercury white' is referred to in 16th-century technical literature on painting. However, although calomel has been recognised in the past as a degradation product of cinnabar in both wall and easel paintings, its deliberate use as a pigment on cultural heritage objects has only been documented recently in white areas painted on 17th-century South American objects. The present study describes the first ever verified use of calomel as a white pigment on European works of art, both of which predate its documented use in South America.