what are the differences between colorfast and non colorfast pigments?
I'm sure with enough research you will be able to find these answers and explanations in your text book. Or google them, maybe it will have pics to help describe if your more of a hands on learner. Good Luck.
Pigments, are generally solids and are usually insoluble in the medium in which the pigment is being used. Pigments, are typically used instead of dyes in applications where color migration or bleeding is undesirable. One possible approach to create a colorfast pigment for use in something like toothpaste would be in a layered anion exchange material which is contacted with the dye under conditions in which a water-insoluble pigment is obtained. The water soluble dye and the layered anion exchange material would normally be contacted together in a liquid medium in which the dye has been dissolved. The layered anion exchange material is preferably a layered aluminate of some kind. Generally, pigments are graded by international standards for color fastness. Eight is the most color fast, and anything over six will do quite well out-of-doors. As ancient Frescoes, sand paintings, petroglyphs and other pure-pigment art demonstrate, certain pigments can remain in direct sunlight for thousands of years without any indication of fading. These pigments are earth, metal, and chemical colors that are neither dyes nor tints. Dyes and tints, such as alizarin crimson, berry juice, etc. will bleach quickly due to ultraviolet exposure that occurs in direct or indirect sunlight. Today most paints are derived from much different sources than they were as recently as fifty years ago. Real cadmium, cobalt, copper oxide, to name a few, are no longer used. They are now formulated to appear similar to the traditional pigments. They may be extended out with white, resulting in an appearance that can differ with traditional counterparts. For the most part these new colors are very colorfast and without the addition of medium or varnish they will not fade when left in direct sunlight.
