In 1899, Christiana Herringham translated "The Craftsman's Handbook," a manual for artists written by an Italian named Cennino Cennini in 1450. When Cennini wrote his manuscript, tempera painting had been perfected by centuries of trial and error but by the 19th century much of that knowledge had been lost. Herringham's translation brought the ancient technique back to life and generated a revival of interest in tempera painting which has continued since.

Contemporary tempera painters have developed variations on Cennini's methods, but the technique remains essentially the same. The first step is to prepare a traditional gesso by mixing crushed marble or precipitated chalk with rabbitskin glue. This is heated and applied in six to eight coats to a masonite panel (the Italians used either poplar or linden wood panels). After drying, the surface is smoothed by a wooden block dipped in water. The panel is then lightly sanded and left to cure for a few days before painting.

The paint is prepared by mixing powdered pigments with egg yolk and distilled water. Chicken's eggs are generally used, though Russian icon painters prefer goose eggs because they have a higher oil content. The paint is then applied in very thin layers to the panel. Cennini's technique calls for executing the entire first layer in a monochromatic tone (black or brown and white), then glazing in the colors. In principle, this is still done by contemporary tempera painters, though they may do the underpainting in different colors. Eventually, many layers of transparent paint are applied, working up into the highlights and down into the shadows. It is this "layering" which gives tempera its unique quality. If done carefully, the tempera painter can create optical effects that can't be obtained by any other medium. No finishing is required. Over the course of several years, the surface will harden and become more durable than any oil-based varnish.

Egg tempera is difficult to master. It is unlikely to ever become a "mainstream" medium, but it has a devoted core of practitioners, as well as collectors, around the world.

To find out much more about tempera in all its forms the site to visit is   www.eggtempera.com