See P. Albenda, Creative Painting with Tempera (1970).
Tempera (also known as egg tempera) is a type of artist's paint and associated art techniques that were known from the classical world, where it appears to have taken over from encaustic and was the main medium used for panel painting and illuminated manuscripts in the Byzantine world and the Middle Ages in Europe, until it was replaced by oil painting in Europe. It has remained the required medium for Orthodox icons. It is paint made by binding pigment in an egg medium. However, the term tempera in modern times is also used by some manufacturers to refer to what is called in America poster paint, which is a form of gouache that has nothing to do with real egg tempera.
One might observe simply by washing breakfast dishes that egg yolk dries quickly and adheres firmly. Tempera was traditionally created by hand-grinding dry powdered pigments into egg yolk (which was the primary binding agent or medium), sometimes along with other materials such as honey, water, milk (in the form of casein) and a variety of plant gums. Many of the Fayum mummy portraits use tempera, sometimes in combination with encaustic. Oil paint was invented in the north of Europe during the Middle Ages (Theophilus mentions oil media in the 12th Century) and was the principal medium used from the 15th century in Early Netherlandish painting in northern Europe. Italy, Greece, and Russia were the major centers of tempera painting. Around the year 1500, oil paint replaced tempera in Italy. Tempera continued and continues to be used in Greece and Russia. In the nineteenth and twentieth centuries there were intermittent revivals of tempera technique in Western art, among the Pre-Raphaelites, Social Realists, and others.
Tempera paint dries rapidly. The techniques of tempera painting can be more precise when used with traditional techniques that require the application of numerous small brush strokes applied in a cross-hatching technique. The colors, which are painted over each other, resemble a pastel when unvarnished, and are deeper colors when varnished.
Tempera is normally applied in thin, semi-opaque or transparent layers. When dry, it produces a smooth matte finish. Because it cannot be applied in thick layers as oil paints can, tempera paintings rarely have the deep color saturation that oil paintings can achieve. On the other hand, tempera colors do not change over time, whereas oil paints darken, yellow, and become transparent with age.
Tempera must be applied to an absorbent ground that has a lower “oil” content than the tempera binder used (the traditional rule of thumb is “fat over lean", and never the other way around). Since the ground traditionally used is inflexible Italian gesso, it is preferable for the substrate to be rigid as well. Historically wood panels were used as the substrate, and more recently un-tempered masonite and modern composite boards have been employed. Heavy paper is also used.
Most often only the contents of the yolk are used. The white of the egg and the membrane of the yolk are discarded. After isolating the yolk and drying the membrane slightly by rolling it on a paper towel, pick up the yolk gently by the membrane, dangle it over a receptacle and puncture the membrane with [for instance] a toothpick to drain off the liquid inside.
If the paint contains too much yolk, the paint will look greasy and clumpy; too much water makes it run. So makers of paint have to finely adjust the amount of water and yolk to achieve a consistent paint. As tempera dries, the artist will add more water to preserve the consistency and to balance the thickening of the yolk on contact with air.
Different preparations use the egg white or the whole egg for different effect. Also other additives such as oil and wax emulsions can modify the medium. Adding oil for instance in no more than a 1:1 ratio with the egg yolk by volume will produce a water soluble medium with many of the color effects of oil paint, although it cannot be painted thickly.
Many of the pigments used by medieval painters, such as Vermilion (made from cinnabar, a mercury ore), are highly toxic. Most artists today use modern synthetic pigments, which are less toxic but have similar color properties to the older pigments. Even so, many (if not most) modern pigments are still dangerous to be used without care, and precautions such as keeping pigments wet in storage must be taken to avoid breathing their dust.
Other practicing tempera artists include Linda Paul, Michelle DeMarco, Robin-Lee Hall, Fred Wessel, Philip Aziz, Michael Bergt, Rob Milliken, Neville Sattentau, Koo Schadler, Phil Schirmer, Ernst Fuchs, Antonio Roybal, George Huszar, Altoon Sultan, Grégoire Michonze, Sarah Mceneaney, Peter Messer, Shaul Shats, Lalu Prasad Shaw, Jon Gernon, Alex Garcia and Sandro Chia (e.g. Studio 1986).