"For the use and good and profit of anyone who wants to enter this profession."
-- Cennino Cennini, sometime before 1437
Making the Egg Medium
Medium is what is mixed with dry powdered pigments to make paint. The egg medium is what makes this paint egg tempera.
Prepared egg medium lasts up to three days in a cool environment. Some people add a drop of oil of cloves to help it last, but I have never found this necessary
You will need:
- One very fresh egg, preferably organic (it really does make a difference)
- A paper towel
- An eyedropper
- A clean container for your egg mixture
- Distilled water (tap water will probably do, but it's better not to risk mineral contamination causing probems down the line)
- A needle, toothpick, or other small, sharp object to pierce the egg yolk
- Something to stir your mixture with; the clean stick end of a paintbrush works fine.
1. Crack the egg and separate the yolk from the white. Many people tip the yolk back and forth between eggshell halves until the white is removed, but I just drop the egg into my hand and let the white slip through my fingers.
2. Roll the whole yolk onto the paper towel and, picking up the corners of the towel, roll the yolk around gently until the white is absorbed off.
3. Using your thumb and first two fingers, very gently pick up the yolk. This is possible because with the white cleaned off, the membrane of the yolk will be damp and very slightly sticky, like a frog's skin.
4. Hold the yolk over your container. With your small, sharp object pierce the bottom of the yolk. Gently squeeze the contents out into the container and discard the empty membrane.
NOTE: If at any point before this the yolk accidentally breaks, you can fling, scoop, or grab using your fingers or the container to salvage what you can. A little bit of white in the yolk is not a disaster, and other egg bits, even the membrane, can be fished out.
5. Using the eyedropper, add distilled water to the yolk, the same volume as the yolk. Your average "large" egg seems to have a yolk of about 10 milliliters (two teaspoons).
6. Stir the water-and-egg mixture well. It will be less golden than pure yolk, more milky, and more or less the texture of light cream.
Ta da! You now have your painting medium, which will be mixed with pigments to make egg tempera paint.
The next step is to prepare the pigments.