Expect that to start appearing within the next several weeks, although of course, it takes time to show up on the labels in the stores as they rotate stock through. Environmental Impact. (Lightfast enough for what is never explained.) But based on the Handprint results, which were across the board for all brands he tested, we think you should feel confident in using colors having Phthalo Blue as being quite durable. Thus, samples of artist's pigments may be tested by exposure to direct sunlight, even though paintings are normally displayed under much weaker indoor lighting. III. Excellent lightfastness. This distinction is essential to understand if you want to get the right pigments in the watercolor paints you buy. Added white paint is an acceptable ingredient in oil paints, but is generally something to avoid in watercolors. In the last issue of Just Paint we discussed why some QoR Watercolors had a Lightfastness rating of NA, or Not Applicable, while most carried the familiar ASTM Lightfastness ratings of I and II. 1.3 Lightfastness categories are established to which colorants are assigned based on the color difference between specimens before and after exposure. For example, each colour type is applied to a standard ground using typical applica-tion techniques for that particular colour (for HORADAM® watercolours, this would consist of defined scumbles on artists’ water-colour paper). The ASTM projections seem to me charitable and optimistic. The current solution is the blue wool textile fading card or blue wool scale (at right). Painters have no effective control over these upstream environmental impacts. All modern industrial powdered pigments are shipped in "pure" form, all paint manufacturers premix the paint ingredients before milling; all genuine gum arabic is harvested by hand, etc. (top) unexposed; (bottom) exposed to sunlight for 800+ hours. Soon knowledgeable collectors such as Ruskin and the museum curator J.C. Robinson were publicly voicing concerns about the permenancy of many commonly used art materials. The typical museum policy permits the display watercolors considered "lightfast" for no more than three months in a period of three years at illumination levels from 150 to as little as 50 lux; "fugitive" historical watercolors may not be displayed at all. This sets up something of a quandary, which the ASTM Subcommittee will need to wrestle with. These define industry minimum standards for commercial paints the best quality paints should easily exceed them. A tedious process, but we discover that their two cobalt violet paints are actually convenience mixtures of three (cobalt violet dark) or four (cobalt violet light) pigments, none of them genuine cobalt violet (PV14 or PV49); that sap green lake extra is formulated with black pigment (PBk7) plus four (!) The spell is broken, and you're a free spirit again. To perform the lightfastness test, a blue wool scale is exposed alongside the paint samples. In all cases, again, these names tell you nothing about what is actually in the paint. Once the ASTM approval process is complete, we will then do a final update to reflect the official ASTM Lightfastness ratings. Part of the problem is that most of the ASTM ratings trace their origins back to testing done in 1977 and often using pigments from a single supplier. This is important for the simple fact that even those paints with extremely lightfast pigments may change colour if the wrong binders or additives were used. Every paint manufacturer I know of does not respect the letter of this standard, especially for historical color names carmine, madder, sepia, indigo, van dyke brown, gamboge, emerald green, and any color name with sienna, umber or earth in it. If you do use raw pigment for any reason, you should wear a face mask or filtering respirator mask while you handle the pigment and while you clean up after work.
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