Saint Paul, c. 1460, Vincenzo Foppa, Italian (Brescia), Italian (Brescia), c. 1427/30 - 1515/16, 21 5/8 x 12 1/8 in. (54.93 x 30.8 cm) (image)21 7/8 x 12 1/2 x 5/8 in. (55.56 x 31.75 x 1.59 cm) (panel), Tempera on panel, Italy, 15th century, Saint Paul and Saint Sirus are panel paintings likely from the same large altarpiece. Panel painting was a lengthy process that required many steps. The panel is a plank of wood that was prepared with many layers of gesso, a glue-size-chalk substance that forms the white base layer of the paintings. Gesso is also used to create the raised areas, or pastiglia, seen in each painting: the top of staff and edges of the headpiece in Saint Sirus and areas on the hilt of the sword in Saint Paul. Red bole, a size-clay mixture, was added to areas that were to be gilded with gold leaf. The final step was painting the figures in numerous layers of egg tempera, a paint made of ground pigments, water, and egg yolk.