Since pastels are made of 90-95% raw pigment, it is important to use the correct, good quality pigment to get the best pastels. Some pigments just do not make very good pastels. Some pigments make excellent pastels, but the colors are so hazardous they should not be used either. Below is a beginning list of pigments and their properties as in regards to making street painting pastels. If there is anyone with further experience than what this list suggests in using pigments or making pastels, it would be most appreciated if they would conact me with that info so it can be added to what I have here right now.
Pigments come in different weights, according to what actual chemicals make up that particular pigment. An example of this would be to fill two 8 oz glasses with pigment - one with Cadmium Red and one with Carbon Black. The Cadmium Red glass would weight significantly more than the Lamp Black glass. As a generality, pigments that weigh more tend to be easier to make pastels out of. Pretty much any pigment can be turned into a workable pastel, given the time and resources to figure it out, so don't feel like this list is exclusively all you can use.
Some pigments that tend to make very nice quality pastels are as follows:
Titanium White
Buff Titanium White
Pretty much any of the Cadmiums (*see below)
Burnt Sienna
Raw Sienna
Yellow Ochre
Mars Violet
Mars Black
Mars Yellow
Ferrous Oxide Reds (Red Iron Oxide, Venetian Red)
Cobalt Blue (*see below)
The following pigment colors are workable and generally require a higher wax content to be used:
Prussian Blue (makes a very dark blue)
Pthalocyanine Blue
The following colors are workable with the addition of precipitated chalk added in:
Ultramarine Blue
Pthalocyanine Green
The following colors have eccentric mixing properties and rarely make good pastels, so should be avoided:
Alizarin Crimson
Burnt Umber
Chromium Oxide Green
****Regarding Cadmiums and Cobalts: While pastels made from these bases make very nice pastels both in consistency and vibrant color, these are two pigment bases that are recognized as toxic, especially over repeated exposure. I am told by people who sell pigments that they are both basically stable enough that there probably isn't much danger in being exposed on an occasional basis, but repeated exposure can be very hazardous. You should always wear gloves and a dust mask while using these pigments - This is actually a good safety precaution for all pastels, even the pigments considered "safe". Completely avoid using anything with lead in it - Naples pigments or Lead White, etc. Viridian is also warned against for pastel use.
