Egg tempera is a fast drying medium that is fluid by nature and must be applied thinly in semi-opaque and transparent layers. The binding qualities of the egg does not allow for impasto painting.
Because of tempera's fluid, fast drying property, it is best suited for a more linear style rather than the thick, brushy and painterly technique of oil painting.
Egg tempera has a clean, matte finish and a higher color key than oil. The subtle color variations so characteristic of egg tempera painting are unlike the deep saturated colors typical in oil paints. Therefore, the palette used in tempera only includes the colors which work best in tempera.
The yellow of the egg has very little effect on a tempered color. Any initial discoloring will actually bleach out to a clear tone in time as opposed to oil's tendency to yellow with time.
Underpainting is important. Egg tempera paint is applied thinly and each subsequent layer is affected by the former. While all colors may be thinned to a glaze-like consistency, certain colors, by nature, are more transparent.
One proven method of painting is to alternate layers of warm and cool colors along with opaque and transparent layers.
The layers may be applied quickly and safely over one another because egg tempera sets up fast enough to allow almost immediate overpainting.
Egg tempera does not blend easily like oil because it dries so quickly. This can advantageous because tempera does not become 'muddy' when lighter colors are applied over darker ones.
One can easily renew a color by working light over dark. In fact, a tempera painting becomes richer when more layers are applied, unlike oil's tendency to grow darker with each layer.
Graduated tones are achieved by applying a progressively lighter, more opaque color to the base color, thereby gradually reducing the transparent nature of the paint while lightening the color with the introduction of white.
Whites and highlights may be added at any time, followed by glazes to create rich and resonant tones.
The richest colors are generally added towards the end of the painting process over the body color or an established underpainting.
Pure color may be used for details or rich glazes. Glazing is an appropriate tool to modify colors and unify areas.
Customarily, paint is applied through linear hatching, loose washes/floating with transparent glazes or solid color in-fills.
To in-fill a large area with solid color, make a half paste color mixture. (A paint mixed with enough white to make the color semi-opaque)
A semi-opaque color will help overcome some of tempera's tendencies to show brush strokes and to blend unevenly.
Once a solid color has been laid down, several previously mentioned techniques may be applied to modify the color.
Tempera painters use cross hatching brush strokes to enhance the feeling of volume by following the contours of the forms, instead of applying strokes as if the form were flat.
While tempera may be varnished, historically, varnishes do not dry evenly. They tend to crack and modify the color harmony of the painting.
Instead of varnishing, the surface may be polished to an even sheen with a piece of soft cloth after the painting has dried a few days. This does not have the same effect as the protective qualities of varnish.
Although tempera dries to the touch in a few seconds, the paint does not fully cure for up to nearly a year. To protect the fragile surface from scratching or water damage, frame the piece under glass for the first year. Ensure that the glass does not come into contact the painting.