Guggenheim

This work on paper was recently treated in preparation for the exhibition Solomon’s Gift: The Founding Collection of the Guggenheim. Some of the white highlights were painted by Marc Chagall with a gouache paint composed of lead white pigment (basic lead carbonate). Through long-term exposure to common atmospheric pollutants, lead white will often convert to a dark black compound (lead sulphide). This change usually occurs with watercolor or gouache media. In some instances, other color shifts are observed, such as gray, pink, and brown. This alteration, in certain areas, was deemed to be visually distracting, since the darkened areas created inappropriate forms in the composition. Paper conservator Jeffrey Warda treated these areas by carefully applying a solution that chemically converts black lead sulphide by an oxidation process to a different white compound (lead sulphate). As a result of this treatment, these disfiguring areas were restored to their original appearance.