All paints have three types of components: PigmentsMediaDiluents

Pigments consist of

small particles of colored

compounds.

Are derived from finely

ground naturally occurring

minerals: rocks and ores.

Media serves to suspend

the pigments and bind

them to the surface of the

object painted. Examples are: beeswax,

linseed oil, walnut oil,

plaster, gum arabic and

egg yolk.

Diluents such as water,

turpentine, or mineral

spirits allow the painter

to thin the paint to the

best consistency for the

work.

The only two blue pigments available to the medieval artist were the very expensive azurite and ultramarine.

The Egyptians, Greeks, and Romans often used beeswax as the medium for pigments.

The encaustic method was in very common use until the 8th century A.D. and is still used by a few painters today.

In this technique finely ground pigment is mixed in melted wax and applied to the surface.

Waxes are polymers composed predominantly of hydrocarbons.

In fresco painting, the medium and the surface are the same. An aqueous suspension of the pigment is applied directly to a wet plaster of

calcium hydroxide and fine sand. The pigment is absorbed and is bound into the surface as the plaster dries.

Until the 15th century, egg yolk was used as the most common binder

and medium for paints.

Egg tempera is prepared by mixing egg yolks with a slurry of artist's

pigment in water.

Enough water is added to provide the proper consistency for painting.

By the 15th century, oil paints, using vegetable oils as the

medium, replaced egg tempera as the most common paint.

The oil most commonly used is linseed oil which is obtained

from the seed of the flax plant.

The oil does not dry but rather is cross-linked where there are

carbon-carbon double bonds in the oil.

In water paints, the pigments are usually very finely ground

mineral-based transition metal compounds.

The vehicle is an aqueous solution of gum Arabic, a resin

prepared from the sap of the African acacia tree.

This resin is a translucent water-soluble polymer.

The resulting paintings usually retain a translucent quality;

they appear bright in part because the whiteness of the paper

is reflected through layers of the paints.

These paints use an aqueous suspension of both the pigment and

monomers of compounds such as methyl acrylate and vinyl acetate.

The paint does not become plastic until the monomers combine.

In a process similar to the "drying" of oil paints, these monomers

are linked together by a chain reaction to form a polymer molecule

that is insoluble in both water and most organic solvents.