Polymer Clay Testing 101
If you work with polymers, you know we are always on a
quest for the perfect clay to meet our needs. I have
been working with polymers for almost 20 years now
and have tried nearly every brand available. Before I
will commit a brand to my artwork, I do extensive bake
and strength testing on that clay. This page is
dedicated to showing you the process of those tests.
To the left you'll see a variety of different clays and
colors, marked and baked. I store these tiles for
reference later.
Looking closely here, you'll see "SS" on the tile to the
upper right. This indicates that sample is pure Super
Sculpey with nothing added.
 
Notice the spots in the tile below that sample. Those
marks are what we refer to as a 'moonie', not a good
thing! Our goal is to find a clay or clay blend that will
eliminate this problem.
In this photo you'll see that same tile with the moonie
marks, then one that says "2 P-1K".
This indicates this example is 2 parts Premo and 1 part
Kato clay. This allows me to keep track of the results of
the vast number of test tiles I have....
This example is of a newer polymer clay, Kato clay in
the flesh color.  This clay is remarkably strong, in my
opinion, it is the strongest polymer clay available. It has
some challenges in working with it-it has a more elastic
quality- but I use it exclusively now in the fins on my
mermaids. No worry of tiny tendrils breaking! It's
actually flexible.
Here is a shot of several samples.  Notice the thin
strands of clay, some tied in knots. I love this test! Very
few brands can pass the knot test. I roll out thin strands
of the clay, like a cooked spaghetti noodle. Bake these
according to the manufacturer's instructions.  Once the
clay is cool, bend the strand to see how strong the clay
is. If it doesn't snap, then continue and tie the clay into a
knot, pulling with a fair amount of pressure. You'll see
the clay turn a lighter color where it's strained, but some
clays won't break!  This is so important so we can
create art that will last a lifetime or longer for our
collectors. The brands that will pass the knot test are
Kato, Puppen Fimo and Cernit.
Looking closer now, you'll see that I have written on the
tiles so I know exactly what is in that example. While I
mark the front with a needle tool before baking, the
writing just makes it easier to reference later.  Also,
you'll see the sample marked "Cernit Nougat".  This is a
straight sample, nothing added. I do this because some
clays look very different after baking from what the color
appears to be in the package. We don't want any
surprises, so I bake a sample first- that way I'll know
what the finish color will look like.
 
I also bake simple hands, then see how much pressure
it takes to break a finger.
In 2005 Eberhard Faber released a new Puppen clay.
(Puppen means 'doll' in German) Puppen clay has been
around for years. It's a German made clay and has been
popular for doll making. They changed the formula to
make the clay more translucent and while the new
product is a dream to work with, it did have problems
with white marks, or moonies. I have been working with
blending different colors together to try to eliminate or
greatly reduce this problem. This sample is Puppen,
and the ratio is 2/3 Natural Puppen, 1/3 Classic Fimo
flesh #43, and a small amount of Classic Fimo white #0.
This sample consists of Rose Puppen mixed with
Porcelain Puppen. We can still see the moonies...
 
The addition of a solid pigment clay like white Fimo
Classic #0 does seem to help mask the moonie
problem. It also tends to have the user thoroughly blend
the clay, (a good way to work out those air pockets that
cause moonies) since the white takes a good deal of
energy and time to get worked into the clay. So, adding
white actually serves two purposes. It helps to hide the
moonies and assures the clay is completely
conditioned.
(*See my tutorial on clay blending.)
Once I established which combination of colors of the
Puppen clay made the nicest flesh tone for my use, I
made a sample card. Each example, starting way to the
left, has a little more white added- until we come to the
last example, #10, which was my best result. My goal
was to get the best color and translucence and still
avoid moonies.
 
Way to the left is straight Puppen in Rose color. The
next single sample is 2 parts Rose and 1/4 of 1 part
white. They continue with less and less white- until
sample #10, which is 15 parts Rose Puppen and 1/4 of
1 part white.
The two sample tiles to the left of the large example are
straight Fimo Classic flesh #43.  I put them on this card
so I could compare colors after baking. I was amazed at
how much more yellow the Fimo Flesh color was...
 
The large sample is also put there for color comparison.
That example is Natural Puppen, Classic Fimo flesh and
Classic Fimo white.  We can still see a few moonie
spots. Moonies are caused by air, trapped below the
surface of the clay. Once heated, they expand and cause
the surface of the clay to lift. Because the clay is
translucent, we can see that trapped air space=MOONIE.
Again, a closeup view of what we want to avoid, those
dreaded moonies.
 
Also, the small black mark on the lower row of samples
indicate these tiles were baked in a preheated oven. The
other row was baked starting with a cool oven. Some
people feel that starting your sculpt in a cool oven will
avoid problems. I found no difference whatsoever, and
don't recommend starting your sculpt in a cool oven
because some ovens spike during the preheat cycle. A
spike in temperature could be disastrous for your clay.
Also, some ovens preheat with both the bottom and top
elements heating up and this too will scorch your work.
By now you have probably figured out I am pretty fussy about testing clay and the performance of these
clays. For years I worked as a product tester and demonstrator for the major US distributor of polymer
clay products. I learned a lot in the process. One thing I am most passionate about, and that is correct
baking of polymers. It is a scientific, chemical process. That process should not be 'tweaked' to meet a
certain need of a user. Follow the directions on the package of the brand you are using. Do not
underbake your clay, as that will lead to crumbling later and very fragile clay! Bake for the full amount of
time, and the correct temperature as indicated on the label. Use oven thermometers in the oven to make
sure the oven is baking at the temperature you THINK it is. I actually use two thermometers, and check
them against one another, on either side of the sculpt while it's in the oven.
 
Proper baking is imperative for long lasting sculpture.  Please be aware that the time you bake your clay
is not cumulative. Two ten minute bake sessions do not total a 20 minute bake- they total a 10 minute
bake and that is not long enough for most brands. There is a good deal of faulty information circulating
around on clay baking, and I just want to encourage you to follow the information on the label for the brand
you are using, and not the information in an instructional DVD. The author of that DVD does not know
what clay you are using.
 
Follow these simple guidelines and you will enjoy great success in your  sculpting!