* The level of opacity-transparency can vary from one extreme to the other even in the same pigment. Slight chemical variations, inert additives, crystal or particle shape and size are commonly used by pigment manufactures and paint makers to tailor the pigment to a specific application. Variations in pigment composition from natural sources, impurities and purification can also effect opacity. The binders used and amount of grinding effect transparency of the paint, a pigment in watercolor may be opaque where the same pigment in oil paints may be transparent. I have used mostly the artist paint or pigment manufacturers rating, published refractive index numbers or other pigment/paint manufacturer info of the most common pigment forms used by artists to determine transparency. Your results may vary.

** Light fastness of pigment colors can vary widely even within the same pigment. Manufacturing process, purity, particle size, binder, additives and fillers all have an effect on light fastness and pigment stability. I have used the ASTM light fastness test results when available, and when unavailable, I have used the manufacturer data sheets and/or individual tests for the ratings. Use the information provided only as a general indication of light fastness in art museum conditions, you should always make your own tests on the final paint formulation.

*** The actual toxic hazards of artist materials in real world practice can be debated. Many pigments and artist's paints are toxic if you ate them, but with a little common sense there is really very little hazard especially with pre-made artist paints. Do not smoke, eat or drink in or near the vicinity of pigments, paints and solvents. Do not put your hands or brushes in your mouth or near your face. Even after they've been cleaned artist brushes may still have traces of paint left in them, so never use your month to point the brush.
Dry pigment powders pose the greatest hazard because they can more easily be inhaled or ingested. Dry powdered pigments can also cling to surfaces, hands or clothing and can be spread and blown about contaminating other areas.
However some simple basic safety precautions can eliminate or reduce hazards to minimal levels. Do not smoke, eat or drink in or near the vicinity of powdered pigments. Do not put your hands in your mouth or near your face. Wash your hands often or use protective gloves. Work in an area safely away from food, pets and children. Dispose of waste in a environmentally friendly way that makes it hard for children or pets to get in to. It is wise to wear rubber gloves and a dust mask whenever working with powdered pigments even those thought to be generally safe.

hue (hue):

When the word "hue" is in parenthesis (hue), it designates an artist color hue that is an approximation of the historical artist's pigment that is not actually part of the paint or pigment manufacturer's marketing name. Not including the word hue in the historical paint or historical pigment name may mislead some to believe it is the genuine historical pigment. When not in parenthesis, it is actually used as part of the artists paint or pigment manufacturer's color name as per the ASTM guidelines.
Artist paint suppliers sometimes use other words to designate a pigment hue or mixed color, for instance, some of them are as follows: Extra, Substitute, Modern, New, Nova, and also the historical paint name followed or prefixed by part of the real pigment name (i.e. Cerulean Blue Phthalo). I believe that some of these pigment hue name designations to be a little less than honest.
A hue substitution for a historical artist's color or natural pigment does not mean it's lower quality paint. Many hues use modern lightfast pigments and generally are much less toxic than the historically traditional pigments. I just think art supply manufacturers should be more up front about it.

Side Notes Column:

The side notes are intended as additional pigment information that may be useful to the artist or worth further study. Many of these notes may be opinion (not necessarily my own), rumor, word of mouth or personal experience and meant as starting point for further research. When possible, next to the comment I have included a link to a reference source in parenthesis (Ref),
The notes were collected from many sources including pigment and art supply manufacturer's literature, art and pigment reference books, artist magazines, art supplier or pigment company's web sites and artist forums. One should always be prepared to do further research into any definitive statements on art materials because many of the "facts" may be debatable even amongst experts. There are many age old myths about artist's paints, art techniques, historical artist materials and natural pigments passed down through the decades with little, if any, scientific proof.
The information here is free and provided "as is", I make no warranty as to the accuracy of the statements. Pigments and making paint are a hobby of mine, I am not, nor do I purport to be an expert authority on the subject of art materials, and this document should be read with that in mind. However if you find any inaccuracies or mistakes please e-mail me and I will research the information and correct or add to it if I feel it's needed.

General notes and loose ends:

Some pigment information may be incomplete. A blank cell means that I have not found valid information on that pigment property or it is not applicable (N/A). A question mark next to any information means that the information may be questionable and needs further study. Pigments that have little potential value to artists have been omitted, but may be added at a later date if the pigment has been discovered to be useful to artists. Many pigments have been withdrawn from the color index but are still included here as one may find old storage of pigments and artist paints. I have also indicated the marketing name brand of artist paints and pigments that are no longer available too, as old paint tubes and pigments may be still be found.

All pigment information was collected from a variety of artist's reference books, art related web sites, paint or pigment manufactures literature and art related forums. Although I have tried to be as accurate as possible a full note for note listing of sources (see below for a reference list) is beyond the scope of this document.