On display in the Sinopias Museum in Pisa is a collection of fresco sketches. Housed in a wing of the old hospital, the sinopias, so-called because they were made with red earth pigment from Sinope in Turkey, are the preparatory drawings for frescoes done directly onto a wall. These sketches were then covered with a layer of rough and fine sand so that the sinopias were permanently hidden. The sinopias on show were made by popular artists such as Piero di Puccio, Buffalmacco, Gozzoli, Taddeo, Traini, Gaddi and Spinello Aretino.
