How colorfast are the pigments used in polymer clay? What products and colors used on polymer clay are the most colorfast? How well is fading prevented by Golden Polymer Matte Varnish with UVLS (Ultra Violet Light Stabilizers)? I hope this test answers these questions. If you’re selling pieces and can’t control how they’re stored or used, it’s important to know.
I baked ten strips of white Cernit and applied the following twelve products in five colors: yellow, red, blue, brown and black.
- Kato Polyclay
- Fimo Professional (except for Chocolate Fimo Soft)
- Cernit Number One
- Pardo Art Clay
- Genesis Heat-Set Oils
- Golden Acrylics
- Folk Art Acrylics
- Ranger Adirondack Alcohol Inks
- Jacquard Piñata Alcohol Inks
- Winsor & Newton Professional Watercolors
The polymer clays and pastels were baked for 30 minutes at 275˚. That seemed like a good average temperature, though it’s hotter than recommended for Fimo, Cernit and Pardo and cooler than Kato needs. I don’t believe curing temperature will affect the colorfastness of the pigments used in polymer clay.
The paints and inks were applied to baked clay. The clay was sanded before applying the watercolor so it wouldn’t bead off. The watercolor was also sealed with Sculpey Liquid Clay so it wouldn’t scratch off. The Sculpey Liquid Clay, Genesis Heat-Set Oils and acrylic paints were briefly heat-set with a heat gun.
The alcohol inks were applied last. They were not heat-set because heat can alter their color. The pastels were sprayed with Helmar Crystal Kote matte fixative because they were smearing. The Helmar spray gives some UV protection. (Thanks to Ginger Davis Allman for finding this alternative to PYM II.)
Then I cut the strips in half lengthwise and put the top halves in a dark cupboard. On the bottom halves, I applied Golden Polymer Matte Varnish with UVLS over the left quarter of each color, so each swatch is divided as follows:
Then I placed the bottom halves in a south-facing window. I live at 8500 feet and it’s usually sunny, so they’ll get plenty of ultraviolet rays. Hopefully this test will give an accelerated example of what can happen.
QUALITY OF COLORS
Products are always changing, but in general, pigments are known to be less fugitive than dyes. For more about this important difference, read this article at The Blue Bottle Tree. Also consider that student grade products are less expensive because the manufacturer may have saved money by using colors that aren’t as lightfast.
In this test I used very basic colors. I tried to use similar colors for each medium, but availability varies. Where I had a choice, (with Golden Acrylics and Winsor & Newton Watercolors), I used colors labeled the most lightfast.
When the manufacturer doesn’t offer such labeling, pigments that have withstood the test of time, such as alizarin crimson, cadmium red and yellow, yellow ochre, cerulean blue, ultramarine blue, cobalt blue, cobalt violet, viridian, chromium oxide, raw or burnt sienna/umber or ivory black should be more reliable than a color named “sky blue,” for example.
For in-depth information about pigments, paints and art materials, The Artist’s Handbook of Materials and Techniques by Ralph Mayer is a good reference book. It’s been reprinted since 1940 and is considered the “artist’s bible.”
WHAT I THINK WILL HAPPEN
I’m guessing the dye products (alcohol inks) and the cheaper Folk Art brand acrylics will fade first. The pigment products (pastels, oils, acrylics, watercolors and polymer clays) will be slower to fade. Overall, the reds will fade first because they’re notoriously fugitive. The black and brown pigments will fade very little. The black and brown dyes may not fare as well.
It will be enlightening to see what really happens and how long it takes. I’ll post comparison photos at regular intervals.
One day later, January 29th AM: The Golden Polymer Matte Varnish with UVLS is visibly lighter on some of the darker swatches and the alcohol inks than when I first applied it. According to the Golden website, “There is no way of applying a satin/matte finish to a dark color without lightening it.” The matting agents make it lighter. OK. I didn’t know that. If I cover it with a gloss finish UVLS, it would be less obvious.
Four days later, February 1st: Two of the alcohol ink swatches have gotten darker: the yellow Piñata and the blue Ranger, which I’ve marked with red circles. The blue is more noticeable than the yellow. This is probably an effect of solar heat as the alcohol inks were not heat set. I measured the temperature of the surface of the clay with an infrared thermometer at noon on a sunny day and it was 95˚F to 98˚F–not terribly warm compared to an oven. The UVLS coating made no difference in preventing this darkening.