Permanency
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(Excerpts from ART HARDWARE: The Definitive Guide to Artists’ Materials, by Steven Saitzyk © 1987) Oil paint has been used for several hundred years, and its range of permanency is well established. Although oil paint is subject to some yellowing and cracking over the centuries, it is still a highly durable medium. Acrylic polymer paint, on the other hand, has been in use only for several decades. Its range of permanency is not established, but is instead implied through accelerated aging tests. Although aging tests have often proven to be quite accurate, they can never take into account all the variables. For example, acrylic and vinyl polymers seem to be more vulnerable to weakening from exposure to ultraviolet light (clear acrylic sheeting used in displays and picture framing does yellow in time from the ultraviolet light in sunlight and fluorescent light) and sulfur air pollutants than previously thought. This is not to say that such paints are unsafe, but rather that all the data are not yet in and there is still some uncertainty as to the actual longterm stability. As an example of this uncertainty, Binny and Smith rate its most permanent colors in Liquitex, artists' acrylic emulsion paints, as having slight or no color changes after the equivalent of one hundred years of indoor museum exposure. Many of these same colors in oil paint often carry a rating that is equivalent to two hundred or more years before any visible changes occur. Oil paint with ratings of seventy five to one hundred years are often classed only as durable. Again, the point here is not that acrylics will not last as long as oil paint, but rather that no one can yet say, even with accelerated aging tests.
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