Eggs are a useful source of protein, iodine and essential vitamins and are almost indispensable to the cook, But I use them to paint icons. Chicken eggs are most frequently used. Duck eggs, seagull eggs and quail eggs are less frequently used, hard to find, and too greasy to work with. I can’t use a Quail egg because they are so cute. Goose eggs and ostrich eggs are considerably bigger. Unless I learn to paint egg tempera with an enormous brush I believe I could never use one of their yolks in an entire day.
The simplicity of the formula is magnificent: million year old dirt combined with pure egg yolk, mixed together to create the divine image. The egg is cracked open, separated from the white, rolled in a napkin until the membrane can be pinched and the contents drained into a glass, the iconographer uses only the raw potential for life contained in the yolk. Mix the yolk with 4 to 8 parts water and a teaspoon of vinegar as a preservative. An egg emulsion can be used 2 or 3 days if refrigerated. The emulsion of pure eggs is modified with water continually according to each pigment and the application and style of each iconographer. The dried pigments, finely ground stone, can be purchased from any fine art supply store, it is suggested you begin with only a selection of 12 to 20 pigments (see sources).
The very nature of egg tempera does not give fast results, due in large part to the drying time required and the number of layers involved in achieving a desired color or texture. A finished icon remains fragile for 2 weeks, but after the egg emulsion dries for many months the paint becomes hard and durable. Eggs are so strong, smile.