On Tempera Painting

Letter

The recipe for tempera has been around since ancient times and has long since proven its durability; there are well-preserved examples of tempera from several millenia ago.

Egg tempera consists of egg yolk, water and oil. The standard ratio of 1 to 1 to 1 can be varied to suit one’s own tastes. The recipe is simple and the paint mixture is absolutely nontoxic. Certain pigments used to color the tempera, however, are extremely toxic and can pose a serious health risk.

To make the paint mixture, simply combine the egg yolks, oil and water in a container and agitate them. (An interesting characteristic of tempera is that the yellow of the egg yolk won’t influence the pigment’s color frequency when the paint has dried.) Using purified water in the paint mixture will prevent the appearance of chalky stripes on the painting’s surface.

In addition to oil and proteins, egg yolk contains the substance lecithin. Lecithin is what makes the emulsion between water and oil possible: instead of separating, lecithin allows one liquid to disperse in the other in the form of very tiny bubbles.

The pigment is then incorporated into the paint mixture. The amount of pigment used is, of course, a determining factor for the final mixture; it is important to be aware that certain pigments on the market are more finely ground than others. In addition, certain pigments react differently to tempera mixtures. With a little practice, however, it’s rather easy to achieve the desired color and consistency for your mixture.

The process can be varied depending on the results desired. Measuring the pigment in a measuring cup reserved for this purpose is advisable; in addition, a journal detailing the mixtures can help determine what works well for you – and what doesn’t.

A container with a lid can be used to mix pigments together. Do remember to wait until the pigment dust has settled before opening the lid. Inhaling pigment particles is imprudent, as certain pigments contain toxic substances that can also harm fetuses. For that reason it is unadvisable for pregnant women to work with pigments.

There are several lists detailing the toxic substances. With very few exceptions, pigments containing heavy metals have been taken off of the market for private use.

Handling pigments with care and common sense greatly reduces the potential health risks associated with tempera painting. A good method for preparing the mixture for use is to carefully transfer the pigment mixture into a large bowl and add enough liquid to make a pigment paste with a palette knife or a spoon. Add more liquid and incorporate it with a wide paintbrush. The tempera mixture is then ready to be applied using your paintbrushes of choice.

How a painting’s surface will dry depends both on the paint mixture and the ground to which it has been applied. Unlike oil-based paints, egg tempera dries rather quickly, but it is essential to remember that tempera does indeed contain oil. Oil does not dry; it oxidizes, or combines chemically with oxygen, and the process can easily take several weeks to complete. Thus, the final result may be assessed 5 to 7 weeks after the paint has been applied.

Applying tempera to an absorbent ground allows for a vivid finish. The ground absorbs the water contained in the mixture, while the oil and pigment remain on the surface. Instead of resting like a film on the pigment, the oil bears the saturated pigment from under the surface, resulting in a uniquely matte and silky smooth finish.

The ground can be made with a combination of chalk and egg whites. Egg whites are primarily made up of water, but they also contain the protein albumen, which coagulates when it comes in contact with oxygen. Every paintstroke applied to this absorbent ground will affix immediately.

Slaked lime mixed with water has traditionally been used to limewash walls. Using egg whites instead of water produces a variant of limewash especially well-suited as a ground for tempera. Keep in mind that limewashing is done on cloudy days, as direct sunlight has a negative effect on the mixture.

These days egg whites and egg yolks can be bought separately in containers of varying size, from small packs of six to one liter and more. The single liter jugs and the smaller packs containing two eggs each are very convenient for use in painting smaller surfaces and for small-scale experiments.

The pasteurized egg whites and yolks sold in this fashion are preserved with citric acid; the basic pH of chalk makes it a very suitable ground with an almost neutral pH.

I recommend using factory-primed linen for tempera paintings. Woven linen creates a fine mesh net both length- and crosswise. By stretching the canvas with the fabric grain parallel to the stretcher bars, one ensures the even distribution of tension, thus reducing the risk of the canvas being damaged under stress.

For tempera, the canvas is mounted primed-side in. This not only protects the back of the canvas from moisture – including the moisture released from the laminated stretcher bars – it also provides a prepared surface for the chalk and egg white ground.

The first treatment is the application of a saturating layer of pure egg whites. The liquid is absorbed deep into the fibers of the linen canvas, and it creates a film that becomes slightly viscous when the second layer is applied. The first layer should dry one to two days.

After one or two days a second layer consisting of slated lime and egg whites is applied. The mixture should not be too thick, or the layer will dry out and the excess chalk will begin to chip; nor should the mixture be too watery, lest it be little more than another layer of egg white. There should be enough chalk in the mixture to allow for even distribution over the entire surface to be primed. With the application of the second layer, the first layer is reopened. The chalk then rests, sandwiched between these two sticky layers. The second layer should dry for one to two days.

The third layer consists of pure chalk. I find drawing with chalk on the entire surface to be covered to be the most effective method. It also levels the second layer a bit, pulling up some of the dried egg whites. When the canvas is covered in a layer of chalk dust, the chalk dust is ground into the canvas with the palms of the hands, sending excess chalk dust onto the floor. The objective is to create the most even surface possible, like gypsum board.

When the third layer is smooth and even and the chalk relatively immovable – it should not be able to be brushed away with a paintbrush – the fourth layer can be applied. Consisting of pure egg white, it will moisten the chalk dust layer and permeate the previous layers. The egg white will dry quickly, so a fairly systematic application will produce the most uniform results. Use the utmost care to ensure that the egg white does not wipe away the previous layers, but truly adds a layer. Should there be any area on the canvas where the previous layers have been scraped too deeply, extra egg whites can be reapplied. The third and fourth layers should dry one to two days.

Depending on the results of the previous treatment, application of the third and fourth layers can be repeated. Again, the objective is to create a smooth, even and uniform surface while retaining the elasticity of the surface. If the ground is too thick or contains too much lime, it will loose its suppleness and risk cracking. Toward the end of the priming process, the surface may be sanded with fine grain sandpaper and the dust gently brushed away.

Meticulous and conscientious priming will allow your craftsmanship to radiate in the finished surface.

When the canvas is primed, work with the tempera mixture can begin. I encourage you to experiment with as many different tempera layers and mixtures as you can.

After painting, brushes, bowls and such can be cleaned with soy sauce.

You may choose to use a pure pigment initially in order to gain experience working with the tempera mixture. When you are comfortable with the priming process and have determined your mixtures of choice, you will discover that you can begin working in a structured way without much thought. Ironically, this autopilot mode is precisely what provides the freedom needed to turn the work into artwork.

Resist the temptation to inspect a drying tempera layer with the tip of a curious finger. The mark will be visible and difficult to repair. After several days, the tempera will begin to take on its silky, matte quality, becoming even more beautiful in the weeks to follow. Remember however that the tempera is 1/3 part oil, and that oil needs 5 to 7 weeks to oxidize. For the same reason, new layers of tempera should not be applied until oxidization is complete, lest the outermost layers begin to crack.

Tempera painting is not a quicker alternative to the oil painting; it is a unique form of painting in its own right. Like oil painting, each layer applied in tempera forms the base for the layer that follows, making corrections laborious at best. Patience, concentration and deriving pleasure from doing a job well and with vigilance are among the most valuable qualities a tempera painter can aspire to embody.