Support Induced Discoloration is a relatively new concept to the art world, new because acrylic dispersion paints are new. Support Induced Discoloration occurs when acrylic paints change color due to pulling up toxins or residue in the substrate. The fluids in the paint leach into the substrate, through the primer and pull up the residue, leaving behind particulate in the paint that discolors it. This is most apparent in transparent gels and mediums but also occurs to pigmented paint. Gesso or primer is not sufficient in preventing discoloration, so sealing or sizing is always recommended.
You can prevent SID from affecting your own work by properly sealing wood panels before use. For more information on Sealing (or sizing) panels, refer to our previous post:
Painting on panel sizing. OR, You can purchase one of Ampersand's already sealed and primed panels, such as Gessobord™, Encausticbord™, Claybord™, Aquabord™ or Scratchbord™. All of these panels have been sealed with Ampersand's Archiva-Seal™ technology.
In the early 1990's, Golden Artist Colors did some significant research with Buffalo State College to discover support induced discoloration and test the degrees of discoloration on different supports, with different acrylic mediums and primers. The results from these experiments led to what we know today about SID.
"SID contamination often goes undetected. In most cases, the paints applied contain a sufficient level of pigment, thus a strong enough color, to conceal the yellowing. However, in a transparent glaze and especially in thick translucent gel layers, SID becomes quite noticeable. SID can transform the appearance of an Ultramarine Blue glaze into a lower chroma, greenish color. Gesso alone will not stop SID, and different gels and mediums have varying degrees of blocking capabilities. The best product Golden Artist Colors produces to prevent SID is GAC 100. This thin medium works best when 2 or more coats are applied directly into the support. Once dry, the canvas can then be primed and subsequently painted with less potential for discoloration. Pre-primed canvases can be sealed with GAC 100 as well. Apply one or two coats onto the surface, and follow with at least one coat of gesso to regain tooth if needed." -- From the GAC website
Golden has neatly packaged the effects of SID on a masonite panel below in video format. You can see for yourself in a few minutes how drastically a piece of art can change in a matter of weeks if the work is not sealed properly.
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