painting continues to be used in Greece and Russia where it is the traditional medium for Orthodox icons. Technique Tempera is traditionally created by hand-grinding dry powdered pigments into a binding agent or medium, such as egg yolk, milk (in the form of casein) and a variety of plant gums. Egg tempera The most common form of classical tempera painting is "egg tempera". For this form most often only the contents of the egg yolk is used. The white of the egg and the membrane of the yolk are discarded (the membrane of the yolk is dangled over a receptacle and punctured to drain off the liquid inside). Egg yolk is rarely used by itself with pigment; it dries almost immediately and can crack when it is dry. Some agent is always added, in variable proportions. One recipe calls for vinegar, but only in small amounts. A few drops of vinegar will preserve the solution for a week. (1:3, 3 parts water, 1 part yolk; other recipes suggest white wine (1 part yolk, 2 parts wine). Some schools of egg tempera use various mixtures of egg yolk and water. Powdered pigment, or pigment that has been ground in distilled water, is placed onto a palette or bowl and mixed with a roughly equal volume of the binder. Some pigments require slightly more binder, some require less. When used to paint icons on church walls, liquid myrrh is sometimes added to the mixture to give the paint a pleasing odor, particularly as worshippers may find the egg tempera somewhat pungent for quite some time after completion. The paint mixture has to be constantly adjusted to maintain a balance between a "greasy" and "watery" consistency by adjusting the amount of water and yolk. 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. Once prepared, the paint cannot be stored. Egg tempera is water-resistant, but not waterproof. Different preparations use the egg white or the whole egg for a different effect. Other additives such as oil and wax emulsions can modify the medium. Egg tempera is not a flexible paint and requires stiff boards; painting on canvas will cause cracks to form and chips of paint to fall off. Egg tempera paint should be cured for at least 3 months, up to 6 months. The surface is