Egg Tempera Painting

Egg Tempera Definition and History: Egg tempera is a type of paint made by adding pigments to a mixture of egg yolk and water. In some instances, oils or waxes are added to the paint; in such cases, the egg acts as an emulsifier, making the mixture watersoluble. Historically, other materials such as plant gum (including gum arabic, the traditional binder for watercolors), casein (a protein found in milk), and even honey were sometimes added. Egg tempera is considered to be the second-oldest form of painting (not including Paleolithic cave paintings, which are thought to have been executed using mixtures of naturally-occurring pigments and saliva or animal fat) after encaustic, a paint made by mixing pigments with hot wax. Both techniques were used extensively by the ancient Greeks and Egyptians; however, egg tempera is most strongly associated with Medieval and Renaissance art from southern Europe, especially Italy (artists in northern Europe tended to favor distempers and were among the first to develop oil paints). Egg tempera is also common in Christian religious painting: the tradition of using tempera in painted icons began in the Byzantine Empire, which lasted from the year 395 until 1453, and is continued in Orthodox Christian church paintings. Egg tempera experienced something of a revival in the latter part of the 19th Century, which continues through to today. Some artists active in the 20th Century who have employed egg tempera include Thomas Hart Benton, Reginald Marsh, Ben Shahn, Paul Cadmus, and Andrew Wyeth.

Working With Egg Tempera:

The Ground: Egg tempera must be applied to an absorbent ground. Traditionally, this would be a gesso made by mixing marble dust or powdered chalk (which have the same chemical composition) with a binder, typically rabbit skin glue. The resulting gesso is quite brittle and inflexible, so it is typically applied only to rigid supports, such as wood panel; untempered Masonite is sometimes used today. Because the paint itself is also largely inflexible, once dry, and susceptible to cracking, egg tempera is rarely used on fabric supports, such as canvas (medieval and Renaissance banners were usually painted with distempers, which are pigments mixed with animal glue, and works on paper were executed in a paint made with egg whites, called glare). Rabbit skin glue is purchased in granulated form; the granules must mixed with water and is then heated in a double boiler so that the glue remains warm without boiling. The glue must be kept warm to be usable, as it congeals when cool (unused glue can be refrigerated and then reheated, but it becomes less sticky with each reheating). After applying one layer of glue to the panel, in order to seal it, marble dust is mixed with the glue to form a gesso “the consistency of heavy cream.” After a number of gesso layers have been applied (often more than ten, with each layer drying before the next is applied), the panel is sanded. The final finishing step is to scrape the surface with a straight razor to remove any small bumps or scratches. Transferring the Design and Gilding: Traditionally, a full-size preparatory drawing, called a cartoon, would then be made. The design would be

transferred by piercing holes along the major outlines of the drawing, laying it on the prepared panel, and dusting the drawing with a black pigment powder, such as carbon black or mars black. The drawing would then be removed, and the line of dots left on the surface of the panel would be connected. In gilded religious paintings, the outline of the figure's head would be cut into the surface of the panel with a knife. Areas to be gilded would be covered with either a bole (a type of red clay mixed with water and glue) or a mordant (a tacky, oil-based adhesive). Sheets of gold leaf would be laid over the bole (which is first re-wetted) or mordant and, once the adhesive had fully dried, burnished. In Medieval times, the leaf would be burnished with a dog's tooth; now, however, polished agate stones (or, you know, spoons) are favored. Sometimes, designs would be stamped into the gilded areas to create pattern and texture. In a process called scraffito, some gilded areas would be painted over, and then designs would be scratched into the paint film in order to reveal the gold beneath. This technique was used particularly to create patterns in fabric. The Paint and Pigments: To make the paint itself, one first separates out the yolk of an egg, then carefully transfers the yolk from one hand to the other until none of the white remains. The membrane of the yolk is then pierced and the liquid drained and collected. This is then mixed half-and-half with water. Pigments have historically been derived from naturally occurring minerals, such as iron oxides; stones, such as lapis lazuli (ultramarine) and malachite; metals, such as lead (which was the main source of white pigment until the 20th Century); plant dyes, known collectively as “lakes,” which are typically “fugitive” or prone to fading; and animal sources—purple dyes were once made from the mucus of a particular species of sea snail, and traditional Indian yellow pigment was scraped from the bladders of cows that had been force-fed toxic mango leaves. Since the 18th Century, chemists have produced artificial pigments both in order to create new colors and to replace some natural pigments, which can be expensive, highly toxic, or prone to fading. Both natural and artificial pigments can be purchased at most art supply stores. The pigment is first mixed with water to form a paste using either a palette knife or a large rounded piece of glass called a muller. Because the powder is so light (and because many pigments are toxic), a dust mask should be worn during this step to ensure that none is inhaled. A small amount of this paste is then combined with the egg mixture to form the paint. Be aware that not all pigments are soluble in water; these can be mixed with a small amount of linseed or stand oil before being added to the egg mixture). Egg tempera is traditionally applied using a small, long-bristled brush known as a script brush. Pure egg tempera dries very quickly, and, as such, two colors cannot be blended on the surface of the painting as they can be when working with oil or acrylic paints. Transitions in tone and color in are made by cross-hatching fine lines of different hues and shades. Varnishes and Aging: Egg tempera paintings sometimes have a chalky, “pastel” appearance. Applying a layer varnish, in addition to helping prevent scratches to the painting, will deepen the color to an extent. Because both wood panels and gluebased gesso expand and contract with changes in temperature and humidity, egg tempera paintings tend to crack over the course of many years (this effect, called craqueleur, is considered by many to be desirable). The paintings are otherwise quite stable, whereas oil paints can yellow, darken, or become more translucent over time.

Process: Materials: 1.

Hardwood panel

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Granulated rabbit skin glue

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Marble dust or powdered chalk (optional: titanium white or other pigment)

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Sandpaper (optional: black pigment powder and a razor blade)

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At least one egg (optional: egg separator)

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Pin or X-acto knife

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Assorted powdered pigments

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Pane of thick glass or marble cutting board

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Palette knife or glass muller

10. Plastic eyedropper 11. Plastic mixing tray with individual wells 12. Size one or smaller script brush 13. Varnish, if desired Preparing the panel:

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Select and cut wood paneling to the desired size.

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Poplar, oak, and other hardwoods are best. Untempered Masonite may also be used.

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If desired, you can stretch canvas or linen over the board, stapling in the back as you would when stretching a canvas over a frame.

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Prepare rabbit-skin glue (steps for individual brands may vary, check package instructions) 1.

Measure the appropriate amount of glue granules and cold water.

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In a jar, allow glue to soak overnight or at least four hours.

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Heat a pot of water over low heat; place the jar in the water and stir periodically until the glue dissolves (I put a ceramic coffee saucer in the bottom of to pot to make sure the glue heats evenly. Note that a warming tray can be also used in place of the double boiler setup).

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Apply one coat of glue to the panel, including the back and sides. Allow to dry.

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Measure and add marble dust or powdered chalk to the glue mixture. The generally-accepted ratio is three parts glue to two parts chalk. Titanium white or other pigments can be added at this point to create a brighter white or tinted ground.

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The gesso should be thin, such that your first few coats will be quite translucent: making the gesso too thick by adding more chalk will make the ground softer and more brittle.

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Using a soft camelhair brush, apply at least eight to ten coats of gesso to the front and sides of the panel in alternating directions, allowing one coat to set up or dry before applying the next.

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Gesso should be kept warm at all times

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Add water if the gesso becomes too thick due to evaporation.

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Allow the gesso to dry at least overnight after applying the last coat.

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Sand with progressively finder-grit sandpapers. Gesso will take on a slightly gloss, burnished appearance.

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Optional: you can lightly dust the sanded panel with a black pigment; this will reveal any bumps or scratches in the surface. You can then use a razor or utility knife to carefully smooth them down.

Preparing the tempera:

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On a piece of glass or other smooth, nonporous surface, measure out a small amount of the desired pigment. Remember to wear a dust mask or respirator at all times when handling pigment powders.

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With an eyedropper, add enough water to make a paste; using either a palette knife or glass muller, grind the pigment mixture until smooth (no lumps should remain). Store the mulled pigments in small plastic containers until ready to use.

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Separate one egg using either your hands or an egg separator.

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Cradle the yolk in one hand and gently roll it to the other. Repeat, wiping your hands on a paper town each time, until most of the egg white is removed (don't overdo it, though, or the yolk will break).

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Holding the yolk at the ends of your fingers, pierce the membrane with a pin or knife.

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Collect the liquid in a small jar and add an equal amount of water.

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The egg mixture will not last more than a day or two, even refrigerated.

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With a palette knife, place a small amount of mulled pigment into one of the wells of the mixing tray.

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Using an eyedropper, add enough egg mixture to make a thin paint, mix with palette knife

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Egg tempera should be fairly translucent, the painting will smudge if you add too much pigment.

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Remember that, because blending is not possible, you will want to mix at least three shades of whatever color you are using.

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Adding a small quantity of damar varnish to the paint mixture will make the paint film more durable, but be aware that it has a tendency to yellow.

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Linseed or stand oil will slow the drying time of the paint and make blending possible.

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If you add more oil-based medium (linseed oil or varnish) than egg, the mixture will no longer be water-soluble. Oilier layers should always go on top of less oily ones (the general rule of thumb is “fat over lean”).

Tips for painting:

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Painting can be applied either as thin lines or broad areas. Shading is achieved by making thin, crosshatching lines with a small script brush, beginning with shadow areas and slowly building up highlights.

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Because of the fine degree of detail common in egg tempera paintings, magnifying glasses can be very helpful in preventing eyestrain.

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Do not apply paint in thick layers, as these will crack or flake off.

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Traditional egg tempera paintings begin with a layer called the verdaccio, a greenish-gray underpainting. Various formulas for the color can be found, most including some combination of terre verte, yellow ochre, burnt sienna, mars black, and white.

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A varnish layer will give the painting a richer, more saturated appearance. It's recommended that your spray the painting with a good-quality charcoal or pastel fixative before applying the varnish in order to prevent blurring or smudging. Note that most varnishes darken or yellow over time.