How Lightfast Are Polymer Clay Colors?

Since a lot of my life revolves around my garden, it goes without saying that many of my art inspirations focus on this subject.   Many of my polymer clay pieces have a garden theme of some sort, in their designs.  On my to-do list for quite some time now , is creating items to use in the garden.

 These items need to be able to withstand exposure to all the outdoor elements, from rain, to freezing, to sun.  Knowing this, about four years ago,  I began experimenting.  I created a design cane, using the six colors of the rainbow, plus black and white.  The brand of clay I used was Kato.  I had intended to also get some Premo, to use for this experiment, but had too many other things going on.

I made a little bird sculpture out of the Kato rainbow cane, fired it, and put it outside in my birdbath, which located in the full sun.  This was in January of 2006.  Being in Western Washington, I knew there would be plenty of water exposure, plus some freezing.  I wedged the little bird between two rocks, so that the top of it was out of the standing water, but the bottom was fully immersed.

I checked on it every couple of weeks and was happy to see it holding up so well.  I had read somewhere that polymer clay items immersed in water might develop a white film.  This did not happen to the bottom of the bird, even as the weather warmed in the spring.  It did, of course, have some green slimy algae form on it, and I would periodically bring it in and scrub it with Dawn dish soap and rinse it off, then put it back.  The algae formation wasn’t any more, or less, compared to the rocks in the birdbath.

In mid-July, since we were just past the peak of our most intense sun of the year, I inspected the little bird.  Unfortunately, I noticed some color shift.  By the end of August, the color shift was very dramatic, so I concluded the experiment.

I studied the sculpture and notated that the color shift was only in the colors purple, red, magenta and orange.  This told me that the magenta Kato clay was the problem.  In fact, the magenta stripe of the rainbow was a very pale pink.  Conclusion:  In Kato brand polymer clay, the magenta color was not lightfast.

Ever since that initial experiment, I have intended to revisit this experiment and do it properly.  Lightfastness is important in art mediums.  Knowing the lightfast rating for an art material is very useful for serious artists.  If you are creating a piece intended for outdoor exposure, it should be able to hold its color for a long time, with little to no protection.   For works of art created for indoor display only, lightfastness is still important.  Art materials with higher lightfast values should be used for fine art projects, where it is hoped the finished art piece will last over a hundred years or more.

Now is an especially good time to do this experiment, in light of the recent reformulations in the major brands of polymer clay.  Because of the formula changes, we cannot assume anything we may have known before 2008 still holds true.  Although most of the brands may not have changed the pigments they use in their clay, it still may be possible that changing other things in the chemical makeup could affect color fastness.

What I will be testing for :

  1. Lightfastness, colorfastness – Will total exposure to the sun affect the color over a year’s time? How will it compare to the same item kept indoors in room with normal indoor lighting?
  2. Exposure to water – both precipitation and submersion.  Are there any affects over time?
  3. Temperatures – Will temperature extremes have any adverse affect on the polymer clay item?  Especially freezing/thawing?  (Side note-this may be hard for me to do, as our temps where I live tend to be mild.  If anyone living in an extreme climate would like to volunteer, I can send them some pieces to test.)

How I Will Do the Experiment

I will test the three major brands of clay favored by the majority of polymer clay artists in the U.S.:  Premo, Fimo Classic and Kato, in their newest formulations. (Side note:  I wanted to consider other brands/types of polymer clay, but not all types are readily available and some are not very durable.)

In each clay brand, I will mix magenta, yellow and blue (or turquoise) to create a rainbow spectrum of these colors:  magenta, red, orange, yellow, chartreuse, green, turquoise, blue, purple and violet.  I will also use solid black and white.  From these colors, I will construct a striped cane, so that I have a rainbow cane, with black and white accents, for each brand of clay being tests.

Using striped cane, versus using a blended rainbow, is very important, so you can see a defined border between each color.  (Side Note:  You may be wondering why I don’t just make striped sheets of the colors or little sticks of each color and put them outside.  I feel making a cane is important, in the remote chance that there would  be any color bleeding between two colors.)

I will use the canes I make, plus the scraps of the cane-making to construct two identical 3-D figures for each brand.  One figure of each brand will be outside, the other, as a control, will be kept inside, in normal inside lighting.

I initially planned to do this experiment with the polymer clay items totally bare and exposed to the elements.  However, I may decide to make a third item of each brand, to which I will apply a clear coating (brand not known yet) with UV protectorant.

 The pieces will be kept outside, in full-day sun exposure, half submerged in water at all times, for a minimum of 8 months.  About once a month, I will inspect the items, compare them to their controls, and report the progress of the experiment.  It would be great if anyone else would like to do a similar experiment and report it here, on this blog post, even if it’s only with one brand.  It would be SUPER great if that person lived someplace like Arizona or Florida.

In addition to reporting the progress and results of this experiment, I will also be posting the color recipes I end up using for each brand, to create the rainbow canes, as well as photos of it all.  If you wish to follow this experiment along over thenext  few months, and/or have any thoughts about how I should do anything differently, etc., please comment and subscribe to this post.

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