subject: How to choose lightfast pigments that last over time ? [print this page] How to choose lightfast pigments that last over time ?
One of the most important factors to consider when choosing pastels is the lightfastness of the pigments. Lightfastness refers to how quickly the color of a pigment fades over time. All pigments fade, but they fade at different rates. A color is considered lightfast if it fades slowly. A color that fades quickly has a fugitive pigment. Sunlight is the enemy of all colors, so some fading is inevitable in sunlight regardless of how lightfast your pigment is.
Artists talk about lightfastness in terms of stability. A color is generally considered to have good stability if it can survive unchanged for 75 years under museum lighting conditions. Excellent stability indicates that the color is unchanged for 100 years or more under museum lighting conditions. Art materials manufacturers generally use pigments that are rated good or excellent, but when you venture into off-brand pastels, kids' art materials, or nontraditional materials, lightfastness can be questionable. You want to select pastels that have good-to-excellent lightfastness to preserve your work for many years to come.
You've probably noticed faded posters or magazine photographs. All that is left is a blue ghost of the former gloriously colorful image. Left in the sun, the printed colors magenta, yellow, and black fade fairly quickly until all that remains of the image is the blue printed image. The blue, or cyan, is the most lightfast ink used in the printing process, so it lasts the longest. That blue, incidentally, is the phthalocyanine blue pigment.
You can easily test to determine whether any material is lightfast. Simply make a sample, cover part of it with anything impervious to sunlight, and leave it in the sun for a few days. If you notice that the uncovered portion is paler than before and has even changed hue, you're looking at a fugitive material.
