Purity and Labeling

(Excerpts from ART HARDWARE: The Definitive Guide to Artists’ Materials, by Steven Saitzyk © 1987 revised 1998)

If this were a car lease, this section would be the fine print.  Material that you really rather not read, but you should.  The term “pure” has been as over employed in reference to paint as it has in reference to food.  It is difficult to derive any practical information from the use of the term.  For example, in the making of the finest artist‑grade oil paint, only C.P., or chemically pure, cadmium sulfo‑selenide (PR 108, C.I.  77196) is used to make a genuine cadmium red color.  Depending on the grade of paint, roughly half the contents of the paint tube consists of oil, with a small percentage of additives.  Consequently, it is difficult to understand what the resulting chemical purity is or means after a pigment has been blended with stabilizers and driers, and in lesser grades of paint where fillers are added as well.

There have been attempts in the recent past to establish some form of stand­ardization in the United States.  These efforts have resulted in Commercial Stand­ard CS98‑62, published by the United States Department of Commerce (a copy can be had by writing to the Superintendent of Documents, Washington D.C., 20025).  It is a voluntary standard allowing those who conform to it to say so in their labeling.  The standard seems to have been written with a manufacturer’s bias, rather than a consumer’s bias, as well as a bias toward middle quality, and would seem to eliminate those manufacturers who produce the worst paint and those manufacturers that produce some of the best paint (primarily in the area of resin‑oil) from using the approved label.  Few manufacturers have ever fully complied with this standard.

Another important outgrowth of the standardization efforts is the use of color names and color indexing for artists’ paints.  Color name and color indexing is a fairly specific method of identify­ing a pigment and establishing purity.  (For information about this seven‑volume index (now on CD-ROM for $700), write to the American Association of Textile Chemists and Colorists, P. 0. Box 12215, Research Triangle Park, NC 27709-2215 or go to www.aatcc.org.  A reference copy can often be found in a university chemistry library or a public library that has a science reference section.)  This information is particularly important to restorers, deco­rators, and paint manufacturers.  Where it could be help to the average artist is if all manufactures supplied both color index names and the color index number for each color the offered on the tubes themselves.  It can be most useful in determining at least the quality of many of the pigments used.  For example, the finest paints, artist grade, are supposed to be made from chemically pure pigments.  The finest cadmium red paint is made only from the purest cadmium sulfo‑selenide, C.I. Name: PR 108, C.I. Number: 77196, and not from cadmium‑barium sulfo‑selenide mixtures such as, PR 108, C.I. 77202, which contains 15 percent barium sulfate, or PR 108:1, C.I. 77202, which contains more than 15 percent barium sulfate.  Such cadmium ­barium mixtures fit into the professional grade because they tend to be weaker in intensity and the paint is more transparent, which is undesirable in a cadmium color.  The movement toward better labeling, so far has met with limited results.  The few manufacturers report color index names, such as PR 108 for cadmium red, on their tubes do not include the color index number, which would indicate the specific pigment.  PR 108 can not only vary considerably in quality, but in color.  PR 108 ranges from light red to deep purple.  All one can tell with only a color index name is whether not there is or is not any cadmium pigment used at all.  This is less than satisfactory.  It is however not impossible to obtain the color index numbers from companies like Winsor & Newton who off the information in a small booklet, “Notes on the composition & permanence of Artsts’ Colours,” which is available on request.

Ideally all tubes of oil paint should display not only the C.I. names and number, but the common color name, the percentage of pigment to oil, the specific drying oil, and waxes or fillers used.  The labeling that we currently have derives from a set of voluntary standards established by the American Society for Testing and Materials (ASTM).  An improvement on the Commer­cial Standard CS98‑62, as well as on labeling.  Voluntary standards concerning health hazards and the labeling of hazardous materials are set down in ASTM D 4236-94, Standard Practice for Art Materials for Chronic Health Hazards.  ASTM D 4302-96a, Standard Specifications for Artists’ Oil and Acrylic Emulsion Paints, deals with improved labeling, while ASTM D 4303-96a, Test Methods for Relative Lightfastness of Pigments Used in Artists’ Paints, attempts to standardize light­fastness test procedures.  A copy of each of these documents is available from ASTM Sales Services Dept., 100 Barr Harbor Drive, West Conshohocken, PA 19428, Phone: (610) 832-9500 Fax: (610) 832-9555 or their web site: www.astm.org for $18 for downloading or fax-on-demand.  Manufacturers that conform to these standards are permitted to say that their product “Conforms to ASTM D 4302-96a.”  Since such labeling is generally to be not found on products, there is little one can do to compare ingredients.  It is important to note that in addition to these guideline being voluntary that the labeling “ASTM xxxx” can be confusing since the ASTM only recommends guidelines for proper testing and labeling, but does no testing of its own.  The supplying of accurate and meaningful labeling, as well as supplemental product information, is still almost entirely up to the good will of the manufacturers of artists’ mate­rials.  The only labeling that has been gaining in momentum and use is with regard to health issues: ASTM D 4236-94.  Its relevance is discussed separately in the chapter on hazards.

Complete labeling, backed up with easily accessible and understandable, in‑depth technical infor­mation, is sorely needed and supplying it would be a great service to the artist.  At the same time it is important not to be too harsh on the manufacturers, because in addition to there being a vast array of products, they are available in many sizes, some so small such as half-pan water-color cakes, and pastels, that detailed labeling on the product is impossible.  Some of the major manufacturers like Winsor & Newton and Lefranc & Bourgeois publish technical guides for artist on some of their products lines, which is very helpful, but more detailed information could still be added.  For the most part, these booklets are available upon direct request to the manufacturer by an individual artist.  They are expensive to print and distribute, but with the increased availability of the Internet the same information could be made available at very little cost per person.

(Excerpts from ART HARDWARE: The Definitive Guide to Artists’ Materials, by Steven Saitzyk © 1987 revised 1998)