Whether
you are making something sculptural or building
millefiore canes, all polymer clays are strongest when prepared for use
first.
Since its
introduction through German doll makers in the 1930's, polymer clays have
changed and been refined quite a bit. In addition to the original FIMO™ ,
there are now many others including Premo™, Kato™ Polyclay, Cernit™,
SculpeyIII™, Modello™ and Dukit™ which are the most widely available.
Each is made with PVC, pigment, oil and sometimes water based plasticisers,
and some have additional components like white china clay and mica. Each brand
has its uses and characteristic traits. Some are softer when raw and more
brittle when baked. ALL clays will have variations from batch to batch; so use
care to make millefiore canes with similar consistencies of clay. Watch out
and try to avoid mixing pieces that are very hard in the same cane with soft
clay---it wont reduce well if you
do.
Most clays
must first be prepared by kneading and rolling. This is called conditioning
the clay. Kato Polyclay also responds well to being hit with a mallet while
still in the package, then sliced and hit some more. Heating Kato makes it
tougher, not softer, though most other clays will soften when gently warmed.
Conditioning is vital to the strength of the finished piece and must be
done no matter how soft the clay may feel. Clean your work surface often and
be aware that clays will dull or even remove finishes from a wood surface.
Ceramic and stone tiles meant for floors are also good work surfaces, staying
cool and easily cleaned. Ceramic tiles are also great for baking---just pop
them in the oven.
To condition:
Slice and chop clay by hand or with a processor. Roll the clay out into a
snake shape, then ball it up, and roll it out again. Or, slice and flatten it
into a pancake about ¼ an inch thick or less, and put it through the pasta
roller at the widest setting ( a #1 on may machines, though some work the
other way and start at #7 or #9) This produces a sheet or "tongue"
of clay. Fold it in half length wise, and place the fold side down in the
roller or along either side but NOT on top—that adds air bubbles. Repeat the
process. Do this several times.
If the clay crumbles, roll it back into a snake and start over.
Some very hard
clays benefit from a little pre-warming; you can sit on them or put packets in
pockets. If you use a heating pad, top of the oven, or other heated surfaces
be aware that clays start to cook at 110 degrees and its very easy to leave it
there too long.
To add small
amounts of oil by hand, coat your hands lightly and continue to work the clay.
Or, you can add transparent clay, which is softer and adds more plasticiser to
hard clays. You can add as much as 1 part trans to 1 part color without much
color change in the final baking. Sculpey Diluent is the plasticiser itself,
and can be added in very small amounts. If your clay is like a rock, try
processing it with any of these, and then put it in a plastic sandwich bag or
wrap the resulting lump with plastic wrap and leave it overnight. This allows
the active ingredients to "travel" and helps to permeate the old
clay with new plasticiser. Then flatten the clay and condition as usual. It
takes a little extra effort, but most old clays can be revitalized in this
manner. However, if the clay is not just old, but partially baked, it may not
be possible to re-soften it.
If your clays
are too soft, they can be made more workable by "wicking" or
"leaching" the excess plasticiser from the clay. To do this, roll
the clay into sheets, and place between two pieces of newsprint or other
paper. You should still be able to fold the clay without cracking, which
indicates that too much plasticiser has been removed. Leigh Ross recommends
putting sheets of clay between sheets of paper and then sitting on it for 5-10
minutes to make sure you don't over-leach. However, be aware that removing the
plasticiser can weaken the final product. For best long term results, we find
it best to allow soft clays to sit packaged and in a cool dry place to
"age". Several months later, its just the right consistency without
loss of strength. I order in bulk during cool months at the beginning of the
year to avoid shipping raw clay in high heat.
A
pasta machine can be used to condition the clay. Versions now available with
motors offer significant increase in ease of use and speed. Machines have the
added advantage of rolling the clay into even sheets of adjustable thickness.
Color blending is also made faster and easier by using a machine. Partial
blending is used for a marbled effect, but individual colors should be
conditioned first, as continued kneading will result in a solid color or shade
that differs from the original colors. When creating a Skinner Blend, the clay
will become conditioned as you roll to create the blend so it can be done
straight from the packages.
Clays can be
kneaded and then left to await your convenience. They will not dry out or
harden unless they are heated--if they are properly stored. Use sheets of
plastic wrap to cover work in progress if you need to leave it for any length
of time, and to wrap cane lengths. Not all plastic wraps are compatible with
clay, but Saran™ with Cling does not interact. Deli-style parchment paper is
also very useful with clay. Hefty™ Baggies are very useful supplies. A two
ounce block of clay rolled at #1 fits perfectly on a Baggie. Place another
Baggie on top. Roll some more clay. Pretty soon you have a stack of colors,
safe from pet hairs and dust, ready for caning. Covering with plastic wrap
helps keep raw clay soft and workable.
Many other
things can also be added to the clays to create some very beautiful effects.
Click here to see some additions
to polymer clay.
Clay can be
coated with Rust-Oleum Varathane
or other compatible gloss finishes, or sanded and buffed after baking. Click
here for more information about stains
and finishes.
Baking &
safety tips
Although polymer clays are
certified as a non-toxic art material, it is always wise to use common sense
and stay on the side of caution. Polymer clays should not be used for items
that come in direct contact with food or liquids including perfume oils or
lotions. Nor should they be used on items that will be heated to high
temperatures or in contact with flame.
The most
important thing to remember about using polymer clays safely is DO NOT
OVERHEAT!! Each brand has specific times and temperatures which are best used
with that clay. Pieces are baked in a home oven (NOT a microwave) or large
toaster oven, at temperatures ranging from 250-300°. Most small projects
require 40 minutes to an hour of baking in a 275° oven. Kato Polyclay bakes
hotter and faster. Be sure to check your package instructions and follow
them.
Watch out for
yellowing or melting. This is not a desirable outcome, and indicates too high
a temperature. Although polymer clays must be heated to the proper temperature
to harden, scorching will begin at temperatures over 300°F and at
temperatures of 390°F toxic fumes occur from burning. Many oven thermostats
are off by a number of degrees, and it is very helpful to purchase an oven
thermometer, and test the various areas in your oven. It’s also a very good
idea to keep tools you use for clay separate from your normal cooking tools.
Don’t bake the cookies and the beads in the same batch! If you bake
frequently, consider getting a separate oven.
Wash your
hands before and after working with polymer clays, or with any of the powders,
inks, finishes and pigments you may
use with it. One good way to remove polymer clay residue from your hands is to
use baby wipes, or lather your hands with soap and a little water and
immediately wipe all of it onto a paper towel or two. Dispose of these, then
wash with soap and cold water. Its also a very good idea to regularly use a
lotion or conditioner on your hands after washing, as dry skin and rough spots
make it harder to smooth your clay projects. You can eliminate the need to
sand or at least make it easier to accomplish by having smooth skin and using
your finger to "pet" the raw clay into smoothness. Your hands are
your most important tools, so take care of them.
Always work
in a well ventilated area. Use an accurate oven thermometer and a timer.
