The sinopia is the preparatory drawing for a fresco, sketched by the artist on the first layer of plaster, creating the outlines of the drawing with a red pigment, the earth of Sinop, which gives it its name.
The original preparatory drawings for the frescoes of the monumental Camposanto are preserved inside the Museum of Sinopias in Piazza del Duomo in Pisa. The frescoes, by Buffalmacco, Andrea Bonaiuti, Spinello Aretino, Taddeo Gaddi, Benozzo Gozzoli, Piero di Puccio and other artists from the Middle Ages and early Renaissance, were damaged or destroyed during a fire caused by the bombing in 1944. On that occasion, they were removed, in order to be restored, and the perfectly preserved preparatory drawings were found underneath. To carry out the restoration work, a pavilion of the Hospital of Santa Chiara, which was designed by Giovanni di Simone, architect of the first Camposanto construction site, was used. The space overlooks the south side of Piazza del Duomo. The Museum stands there today.