Non-invasive identification of white pigments on 20th-century oil paintings by using fiber optic reflectance spectroscopy

Fiber optic reflectance spectroscopy in the 270-1700 nm range was used to identify white pigments typically used in 20th-century paintings and as restoration materials, such as lead white, zinc white, titanium white in the two crystalline forms anatase and rutile, lithopone, and kaolin. Use of the non-invasive, in situ technique was undertaken in accordance with the principles of minimum intervention, which guide the restoration and conservation of artworks. With this technique, a suitable spectroscopic database of the pigments was first created, using various instrumental set-ups. Subsequently, fiber optic reflectance spectroscopy was applied to the study of two paintings from the Galleria di arte moderna, Palazzo Pitti, Florence: Mercato by Elisabeth Chaplin, dating probably from the 1920s, and Renaioli, painted in 1950 by Bruno Rosai. The purpose was to better understand the evolution of the use of such white pigments during the past century, and also to provide useful information concerning questions of chronology.