"For the use and good and profit of anyone who wants to enter this profession."
-- Cennino Cennini, sometime before 1437
Preparing the Pigments
One of the beauties of egg tempera is that you choose whatever colors you want. Any pigment can be used. You are not restricted to what any paint manufacturer chooses to make available. However, for this same reason you should educate yourself as to the properties of the pigments you plan to use. All pigments are fine dusts and are a breathing hazard, and many are toxic as well.
Cennnino Cennini (the author of one of the first how-to treatises in the fifteenth century) says to grind the pigments and store them under water. This is the method I use, and it has served me well.
Please note, however, that there are those who prefer to store their pigments dry and only grind them as they need them. Things can go wrong with water-stored paints: Certain pigments (most notably Ultramarine Blue) can settle into a hard, impacted layer under the water (I just use a strong knife to remove what I need). Certain pigments may grow mold, especially if impurities are present ( I had this problem with some natural Yellow Ochres left in the sun). And if the water evaporates and the pigments are allowed to dry out, they may become brick-hard and very difficult to re-grind.
That said, I feel that leaving one's pigments dry adds a lot of unnecessary work and risk of dust inhalation to each painting project. I prefer to grind all my pigments in water and keep an eye on them.
You will need:
- A frosted glass or stone slab (Porphyry is excellent. Marble is technically too soft, but I use it) and a glass muller (a sort of flat-bottomed grinding-stone with a hande) OR a mortar and pestle (adequate, but it is harder to get all of the pigment cleanly out)
- A scraper or spatula (I use a baker's slice)
- Dry powdered pigment
- Distilled water
- A small clean, sterile jar with a tight lid
- A seriously good respirator, NIOSH-approved (or at the VERY least a dust mask), protective gloves and an apron
1. Put on your respirator/dust mask! Even non-toxic pigments can cause damage if inhaled. I always wear gloves and an apron, too.
2. Work carefully -- You don't want to raise dust! My preferred method is to take the jar of dry pigment, open it, gently pour in a small volume of water (start with about the same volume as the pigment has, but you will have to judge), close the jar firmly, and shake like mad.
3. When the pigment in the jar is thoroughly wetted and there is no dry dust floating inside, open the jar and pour or scrape the wet pigment onto your slab.
4. Begin to grind, gently. If the pigment is too stiff, add more water. Ideally you want a not-too-thick paste. Too much water can make the pigment harder to grind, but if spread out thinly the extra liquid evaporates out pretty fast.
5. Grind round in small circles, and every now and then scrape the pigment back together.
6. When the pigment is smooth, scrape it up and place it in your jar.
7. Cover the pigment with more distilled water (I would err on the side of too much water, rather than too little, see below), and close the jar tightly.
It may be that certain pigments (such as Alizarin Crimson) just will not wet. I find that adding a drop or two of ethyl alcohol ("rubbing alcohol" in common drugstore dilutions of 70%) to the pigment will help the water moisten it. Some also claim a tiny bit of vodka will help.
Almost all pigments will settle over time to a layer of more-or-less toothpast-textured color with water separated above it. For some pigments, such as Ultramarine Blue, this water will be perfectly clear; others, such as most of the Mars colors, will appear murky for years. The water does not seem to excessively thin down the pigment paste.
I prefer to put a lot of water over my pigments. If a wet pigment paste should dry out it will be rock-hard and very difficult to re-wet and re-grind. The extra water is insurance against that occurring.
The next step is to mix the egg tempera paint.