Paintings typically have layered structures consisting of a support, preparation, one or more paint layers, and in many instances, a coat of varnish. The support may be a fabric stretched around a wooden framework called a stretcher or strainer, or itmay consist of a panel made of wood or some other material. The support is usually prepared with a white or tinted ground layer. Next the artist may make an initial sketch or underdrawing on the ground or in some cases transfer the design from well-developed preparatory drawings onto the ground to use as a guide while painting. The paint layer or layers are composed of pigments suspended in a binding medium such as drying oil, egg tempera, plant gum, animal glue, or one of a number of synthetics such as an acrylic polymer. A final coating with a varnish layer, traditionally done with Old Master and 19th-century paintings, is frequently eliminated in modern and contemporary works.
This photomicrograph reveals layering of paint on The Old Guitarist.