Painting
Preparation: most artists prepare a canvas or other surface. A thin and uniform cover or "wash" of white or other color is laid on the whole surface. This may help the later layers to get the same fix all over the surface. Also, the unseen wash may help the reflection of light from the surface, thus improving the effect for the viewer. For really uneven or colored surfaces, such as wood or rough canvas, a more substantial covering is needed. That is called gesso, traditionally a mixture of chalk and gelatin, but nowadays available as a thick white acrylic. Painting on some surfaces requires a special technique. Painting on plaster uses the fresco method.