Pure Egg Tempera - Pigments

Binder - One fresh raw hen's egg.
Diluent - Preferably distilled water, but ordinary tap water does well for most painters.
Pigments - Artist-grade dry pigments. All pigments permanent in oils will be permanent in egg yolk tempera, but the lead pigments (flake white, Naples yellow, chrome yellow and green), as well as cobalt arsenate and emerald green, are usually eliminated today, since they are poisonous and would be handled in tempera as dry pigments. Precautions should be taken in handling all pigments designated as toxic in the section on pigment toxicity. - Pigments for Egg Tempera

EQUIPMENT:

Palette - glass or porcelain
Palette Knife or Spatula
Glass Jars, 2- or 4-ounce capacity with screw tops.
Egg Separator - sold in kitchen supply departments and hardware stores.

PREPARING THE COLORS:
l. Grind each pigment with pure water to a stiff paste. Use either a palette knife or a glass muller and slab to rub up the pigments to a smooth consistency. Some colors that are light and fluffy, such as alizarin and Hansa yellow, tend to repel water rather than to absorb it at the beginning of the grinding or mixing process. Add a little alcohol to these difficult pigments to wet them down before grinding them in water. They will then combine easily with water to make the usual paste. The volatile alcohol does not remain in the mixture after the pigment-water paste is made. Put the pigment-water paste into a glass jar. Cover the jar and tap it on the table a few times to eliminate air bubbles. The pigment-water paste may be stored indefinitely if a little water is poured over it from time to time to prevent it from drying out and the jar is covered tightly. Screw-top covers made of hard plastic rather than metal are to be preferred since they do not rust.

2. Break the egg and separate the white from the yolk by passing the yolk between the shells. An egg separator, such as is used in the cooking, will do the job well, or the egg may be broken into an ordinary strainer...

3. To dry the surface of the yolk in order to remove all traces of the white, pass the yolk from hand to hand, wiping the empty hand on an apron. Soon the yolk will be left dry and free of egg white. Alternatively a paper towel can be used to dry the surface of the yolk. Carefully put the yolk on a clean paper towel and gently roll it around on the towel until the surface is free of traces of the egg white.... Do not dry it so much that it sticks to the paper and breaks.

4. Pick up the yolk firmly between thumb and forefinger and hold it over a clean jar. Puncture the yolk sack with a knife and allow the contents to run into the jar.... Throw away the yolk sack.

5. Add a little water (about 1/3 teaspoonful) to the egg yolk and stir it. This is the binding medium for pure egg yolk tempera.

6. Take a small amount of pigment-water paste from the jar and put it on the palette. Add an equal volume of egg yolk binder and combine them thoroughly by means of a palette knife... This is the egg tempera paint ready to use. It may be diluted with water to a thinner brushing consistency.

Some pigments may require slightly more binder, others less. The paint may be tested in the following way to determine whether the proportion of pigment to egg is correct: Brush out a sample of the paint on the glass palette and allow it to dry overnight. Scrape it from the glass with a razor blade. It should come off the glass in a continuous shaving. If it powders off in small crumbs, the paint was made up with too little egg yolk binder.

The egg will spoil in a short time, usually two or three days in a warm room. Refrigeration or the use of preservatives, such as vinegar, carbolic acid, cloves, or camphor, will retard the spoilage but may affect either the binding strength of the egg or the color of some of the pigments, such as ultramarine blue.

It is the tendency of the egg binding medium to spoil that prevents the artist from grinding large amounts of egg tempera color in advance and storing it in tubes or jars. However, small batches of pigment may be ground directly in egg, without being first made into a pigment-water paste, if the color is to be used up in a short time.

[Kay, Reed. The Painters Guide to Studio Methods and Materials. Englewood Cliffs, NJ: Prentice-Hall, Inc., 1983. pp. 142-146.]