Chromatic alterations of red lead pigments in artworks: a review

Various sources of bibliographic information regarding red lead transformations in artworks are reviewed. Typical examples of red lead use in mural paintings, either as a pure colour or as an admixture with other pigments, are reported. Several cases of red lead discolourations are described here; they underline some debates regarding the alteration process. The role of environmental factors, such as lightening, humidity, pollution or microbial contamination, is emphasized. Recent investigations show that both composition and micro-structural features of red lead grains, which result from the manufacturing process, are determining factors in the pigment alteration process.