Illumination of a mediaeval mystery: the FT-Raman spectroscopic analysis of red pigment from a mediaeval corbel in the church St Clement of Rome, Fiskerton

Microspecimens of vestigial pigment and substrate from a mediaeval limestone corbel (11th Century) have been analysed using Raman microscopy. The deep red pigment is a mixture of red ochre and pyrolusite. The white substrate gives clear indication of a mixture of calcite and gypsum; surprisingly, Raman bands for red ochre are present (but without the added pyrolusite) as are those assignable to a limewash putty as used by Roman decorators for preparing stone surfaces for painting. A weak signal for basic lead white in the substrate is also found. It is suggested that the substrate on which the red pigment has been applied is transitional between Romanesque and Renaissance periods during which the development of gypsum plaster as a base for wet fresco application was made. (C) 2003 Elsevier B.V. All rights reserved.