Minium; FT-Raman non-destructive analysis applied to an historical controversy
The term minium was applied to both cinnabar (HgS) and red lead (Pb3O4) pigments in antiquity; in Roman times, minium was reserved for mercury(II) sulfide but was applied increasingly to lead tetraoxide by the Renaissance. Confusion in the interpretation of ancient recipes for pigment mixtures is inevitable and is compounded by the practice of adulteration of mercury(II) sulfide with lead tetraoxide for economic or artistic reasons. In this study, the Raman spectra of mixtures of cinnabar and red lead were recorded and used to determine the composition of several pigment mixtures from mediaeval artwork. The potential of the method for the non-invasive quantitative analysis of pigment mixtures involving red lead and cinnabar is thereby demonstrated.