A fresco is painting, painted on wet plaster. The process we use at SACI consists of first making the plaster which is a sand, lyme, and water mixture applied to a board. Next the mixture is spread evenly on the board with a trowel. This pushes the sand to the back leaving the wetting ingredients on the surface. Mixed ground pigments (traditionally ground stone or organic mater) is saturated with water and becomes the paint. The process has to be done quickly usually within a 2 hour time before the paster hardens. This can be a bit tricky because dealing with wet paint, it might not dry the color of the materials chosen.