Pigment Degradation in Oil Paint Induced by Indoor Climate: Comparison of Visual and Computational Backscattered Electron Images.

For the first time the degradation of lead white pigment in mature oil paint has been used as an internal marker for the degree of saponification and hence chemical degradation of oil paint. Computational image analysis of the backscattered electron images quantified the degree of the intact lead white pigment versus the nonpigmented and lead-rich areas (degraded lead white) in the paint layers. This new methodology was applied to a series of paint samples taken from four painted wall hangings (dated 1778), which makes it possible to study the influence of indoor climate on chemical degradation of aged oil paintings.