Referring to the table of pigments, we see that a number are toxic, if not poisonous. Unless you're going to make your own, pigment comes supplied in powder form, in small bags or jars. When handling these dusty pigments, it is important to take precautions to protect your health. You do not want to inhale the dust, especially pigments like Orpiment, Realgar and Vermillion – you'll end up poisoning yourself.
1. Place a small amount of pigment on a clean slab of glass or marble. Ensure that the slab is on a stable surface.
2. Add a little water. If using toxic pigments, you may want to add the pigment to the water, to reduce the dust risk as soon as possible.
3. Using a glass muller (I have resorted before now to a large, flat, smooth, hard stone), grind the pigment in a circular motion. Apply a small degree of pressure.
4. If the pigment spreads out too much, use a palette knife to scrape it back into the middle of the slab.
5. Add more water if the pigment gets too dry, a few drops at a time.
6. Different pigments require grinding for different lengths of time. Pigments that derive from stone or earth generally need a lot of grinding.
7. Listen to the pigment as you grind it. At first it will be quite noisy. As the particles are ground down and become finer, they get quieter. When the pigment grinds quietly, it is probably ready. There are some pigments that you could grind until doomsday and they would still benefit from a little more! Good old Orpiment is one of these.
I hate grinding pigment. I must confess that I frequently grind it in the shell as I'm preparing the paint. This doesn't work all that well for indigo or earth pigments.
The binding medium used in manuscript painting, particularly in Europe, was egg. The white of the egg is used most often. Egg yolk is greasier and doesn't stick all that well to vellum or parchment. Having said that, there are recipes for using egg yolk and the proprietary egg tempera paints available use the yolk. Egg yolk gets tougher and harder as it dries. On a flexible surface, it is liable to crack. The general rule is to have a small offcut of vellum or paper and experiment to see what works and what doesn't.
To make egg tempera, you first need eggs. I'm not aware of whether there is any one egg that is superior to all others. Old recipes tend not to say. I would think that they used what was plentiful – probably chicken. There is a marked difference between organic, free range, barn and factory eggs. If you are using the egg yolk, this difference may be very important. Free range, organic eggs have a much richer, deeper yellow yolk. There is also some difference in the colour of the white; organic, again, being slightly more yellow. It's worth thinking about, especially if you're after a lovely, bright white.
Take a thoroughly clean bowl. Break your egg carefully over the bowl, being sure to separate the yolk from the white.
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