pigment mixed with water-soluble glutinous materials such as size and egg yolk
1) Painting made with a pigment ground in gum, usually gum arabic, and applied with brush and water to a surface, usually paper. The pigment is ordinarily transparent but can be made opaque by mixing with a whiting to produce gouache. Transparent watercolour allows for freshness and luminosity. Whereas oil paintings achieve their effects by a building up of colour, watercolours rely on what is left out, with empty, unpainted spaces being an integral part of the work.
2) A color ground with water and gum or other glutinous medium; a color the vehicle of which is water; -- so called in distinction from oil color.Tempera
tempera (tĕm`pərə), painting method in which finely ground pigment is mixed with a solidifying base such as albumen, fig sap, or thin glue. When used in mural painting it is also known as fresco secco (dry fresco fresco (frĕs`kō) [Ital.,=fresh], in its pure form the art of painting upon damp, fresh, lime plaster.
..... Click the link for more information. ) to distinguish it from the buon fresco (true fresco) applied to damp walls. The name distemper is given to the method when a glue base is involved. When used on wood panels, as it most frequently was for altarpieces and other easel pictures, it was applied on a gesso underpainting that was smooth, very white and brilliant. Tempera's particular advantage is that clear, pure colors are produced, which are not so subject to oxidation as are oils. However, tempera does not lend itself to the expression of nuances of color and atmosphere. Well known from antiquity, tempera was the exclusive panel medium in the Middle Ages and the early Renaissance, and in Italy it was not supplanted by oil until c.1500. In the north oil superseded tempera about a century earlier. Tempera was also much used in combination with oils. In modern times there has been a revival of tempera painting. Böcklin and Hodler in the 19th cent. experimented with it, and some 20th-century American artists, notably Ben Shahn and Andrew Wyeth, have renewed an interest in the old medium. Pigment mixed with egg yolk applied to a sized panel is the common preparation. In industrial art, notably for posters, a simplified distemper is often used. An excellent account of the early Renaissance use of tempera is found in Cennino Cennini's Treatise on Painting (c.1437, tr. 1933).