Frequently Asked Questions
About Polymer Clay
To access a glossary of commonly used terms, click here
What
is polymer clay?
Polymer clay is a synthetic modeling material, not an earth clay. It is
formulated from polyvinyl chloride (PVC), dyes or pigments and plasticizer to
keep it soft until heat cured. It is an acrylic art material. There are many
brands of polymer clay available in the United States. They have been
individually tested and certified as non-toxic art materials. Brands vary in how
hard or soft they feel at the beginning of use and the softer clays are more
brittle when cured, and the firm clays are more durable after they are heat
cured.The working properties vary between brands and become a personal choice
requiring experimentation. Some brands or colors within brands contain white
mineral clay that makes colors opaque. Some contain mica that gives it a shimmer
and shine. All polymer clays are thermal set plastics, meaning they are hardened
with heat and do not become soft again after curing. Before being cured in an
oven, clays are thermally reactive and become hard when cool and soft when warm.
For more information about the chemistry and history of polymer clays, click here.
Is polymer clay safe
to use?
When used according to package directions, polymer clays are safe and
fun to use. Polymer clays are extensively tested before being allowed for sale
in Unites States as art supplies. You can read the Materials Safety Data Sheets
(MSDS) for polymer clays online. Click here for reports on FIMO,
Premo and Kato
Polyclay.
Is polymer clay
toxic or poisonous?
Polymer clays are certified as non-toxic. If eaten in large quantities,
intestinal blockages may occur so do not allow babies or pets unsupervised
access. Normal recommended baking temperatures do not exceed 275 to 300
degrees F. The most important thing about baking polymer clays safely is do
not overheat the clay. With most clays scorching will begin at
temperatures just over 300ºF. Toxic fumes can occur at 390ºF. Conversely,
baking at temperatures that are too low will not fully cure the clays and pieces
will become crumbly over time and break.
Watch for darkening or melting indicating the oven temperature is too high. As
many oven thermostats are off by a number of degrees use a free-standing oven
thermometer and test various areas in your oven. Some corners can be hot spots.
Small toaster ovens can burn clays near the heating coils when other areas in
the oven will not be hot enough to fully cure polymer clay. Convection and some
electric ovens will spike while preheating.
The fumes are not toxic unless the clay is burning. Keep your oven in a
well-ventilated area. If you find the odor of curing clay noticeable or even
unpleasant, put your oven in an isolated area. Placing the oven in a cold or
drafty area may cause temperature fluctuations so watch your thermometer. Use an
oven thermometer and ventilate the area where curing is done, regulate
temperatures carefully. If burning occurs, turn off oven and ventilate with fans
and open windows or doors.
For more information, read
this article on Polymer
Clay Safety by Tommie Howell.
Click here to read the Duke
University Medical Center's report on hazard risk assessment from the use of
polymer clay.
Who invented polymer
clay?
One of the earliest forms of polymer clays was invented by Robert
Bakelund as he searched for a synthetic form of shellac. Natural polymers
include shellac, made from Laq beetles, tortoise shell, amber and celluloid and
viscose rayon which are made from tree resins. Bakelund's work resulted in the
formulation of Bakelite. It was extremely popular with designers and had an
early form of polymer clay commercially available in kits, but the phenol base
of uncured Bakelite was flammable and these were discontinued. Todays clays are
non flammable and certified as non-toxic art supplies. FIMO polymer clay was
first made popular by Maureen "Fifi" Kruse, daughter of well known
German doll designer Kathe Kruse in the early 1940s. Though the Kruse family did
not invent the substance that was offered to them for use in the doll making
factory, Fifi used it in making miniatures and mosaics, and it became very
popular. The compound was later sold to Eberhardt-Faber in the 1960's and they
named it after her.
Where can you get
polymer clay?
Polymer clay is available from many craft stores and from polymer clay
Internet sites. Most brands package clay in two sizes; small blocks-2oz. and
large bricks-12oz. There is a list of links to suppliers
of clays and tools on the Polyclay Gallery site.
Where does it come
from?
Polyform is the American company in
Illinois that manufactures Sculpey, SculpeyIII, and Premo. Van
Aken is also based in America in California, and that company manufactures
Kato Polyclay. Eberhardt Faber is based in Germany and manufactures FIMO; and
the most reliable import source for it in the United States is AMACO
(American Art Clay Co.)
Is it like Play-doh
or Plastilina?
No. Those products are not thermal set plastics. The first is a colorful
salt based modeling compound sold to children, and the second is a brightly
colored form of polymer modeling material that does not harden. If heated it
will melt. Plastilina is used by children and by animators who do stop-frame
animation work such as "The Adventures of Gumby". VanAken makes this
material as well as Kato Polyclay, so use caution not to confuse the two.
Is Friendly Plastic
a polymer clay?
No. Friendly Plastic is sold in colorful hard strips that can be heated
and reshaped over and over. It is not a clay, but it is a polymer. Once heat
set, polymer clays can not be re-heated and re-formed.
What can you do with
polymer clay?
Beads, buttons, jewelry, sculptures, dolls, masks, mosaics,
collectables, furniture laminates, decorative items and illustrations
for books and magazines can all be made using polymer clay. In creative hands,
the possibilities are wide open! The exceptions are few--polymer clay should not
be used in items that will be heated to over 300 degrees F, such as incense
burners, smoking pipes, stove trivets, and direct heat cooking or food service
items. Nor is it strong enough for industrial strength uses such as building
foundations or trailer hitches on cars---but when used within common sense
limitations, applications of polymer clay can be extremely varied.
What is Liquid Polymer Clay and how is it used?
Polymer clay is also available in a liquid form which is extremely
useful for bonding raw to finished clay. Liquid polymer clay can also be used to
transfer many printed images. Liquid clays include TLS (Translucent Liquid
Sculpey), FIMO Decorator Gel, and Kato Liquid Polyclay. These range in degree of
transparency and each can be made more transparent by curing at the correct
temperature for each product, and by sanding and buffing the finished piece.
Liquid clays are often used as a glaze or finish on clay surfaces. Pigments and
powders can be added to create faux enamels and other effects.
Sculpey Diluent is not a
polymer clay, it is a liquid plasticizer which can be mixed into any of the
polymer clays to soften old or hard clays.
What is
"conditioning" and why is it important?
All polymer clays must be conditioned before using them in any project,
even the clays that are already quite soft. Conditioning makes the clay more
malleable and softer; it also aligns the molecules and makes it stronger.
Without proper conditioning cured pieces will be fragile and brittle.To
condition polymer clay by hand slice and chop the clay into small pieces. Knead
and roll the clay into a snake shape, stretch it out, fold it over several
times, and roll it back into a snake. Do this at least ten times. Conditioning
polymer clay with a pasta machine simplifies and speeds up the process. Cut clay
into approximately ¼” thick slices. Roll the slices through the pasta machine
on the thickest setting. Stack a couple of slices together and roll them through
together. Stack these, turn them sideways, and roll them through again.
Repeating this process with several slices will form a sheet of clay. Fold the
sheet in half, roll this through the pasta machine inserting the folded edge
first. Do this 20 to 25 times.
How do you know when it is conditioned enough?
One way to know how long it takes to condition polymer clay is to mix colors. Do
the conditioning process with pieces of two or more colors. When the colors are
fully mixed into a solid color, the clay is fully conditioned. Inversely, it is
not necessary to condition clay before mixing colors or before doing a
“Skinner Blend”. The mixing/blending of this color gradation technique fully
conditions polymer clay.
What is a millefiore
cane?
The term "millefiore" is Italian for "thousand
flowers" and refers to the glass making technique used to create colored
patterns in glass using long rods which are placed to form designs, then heated
and stretched to make a "cane". When sliced, each piece has the design
intact and these slices, called "murini"can be reheated and applied to
larger pieces of glass. When used with polymer clay, the colored clay is shaped
and the design is put together like a puzzle to form a cane. The clay cane is
not heated like glass canes, but is manipulated by stretching and compressing
the clay to reduce the design in size as the cane becomes longer and thinner in
diameter. Slices from these canes are used to decorate clay pieces and other
objects in many ways, or can simply be cured and used as buttons,
charms or mosaic tiles. The most
commonly clays used in making detailed millefiore canes are FIMO Classic, Kato
Polyclay and Premo.
What can be done
about clay that is too hard or too soft?
If your clay is very hard, help soften it by using a food processor with
the chopping blade. A few drops of vegetable oil can be added while using the
processor. Do not pour from the bottle, as this is hard to control; instead,
pour a few drops into the cap or a spoon, and add from there. Run the food
processor in short bursts, and don't leave it unattended, as the clay will heat
during use. 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 plasticiser to hard clays. There was a product on the market called
"Mix Quick" that is very helpful for softening hard clay as it
contains even more of the plasticiser than the translucent clay. Another option
is to add Sculpey Diluent, which is the liquid plasticister. For those with
wrist or hand strength problems, or who are working with large quantities, a
pasta roller machine can be used to knead the clay. This has the added advantage
of rolling the clay into even sheets of adjustable thickness.
If your polymer clay is
too soft for your purposes it can be made more workable by “wicking” or
“leaching” excess plasticizer from the clay. Roll the clay into sheets and
place between two pieces of newsprint or copier paper. Leave the sheets between
the paper for only a few hours. You must be able to fold the clay without any
cracking along the fold. Leigh Ross recommends putting sheets of clay between
paper, sitting on it for 5-10 minutes to be sure it is not leached too much.
Removing too much plasticizer can significantly weaken the finished durability
of the clay. For best long term results allow soft clays to stay packaged, in a
cool dry place to “age”. Several months later the clay will be firmer
without the loss of strength leaching can introduce.
How long will it
last and how do I store it?
Polymer clays have a shelf life of between five and ten years if stored
properly. Wrapped and stored canes made six years ago are still usable but not
as pliable as they were within the first year. Storing canes in the refrigerator
or freezer is not advisable as this causes the plasticizer to weep out of the
surface of the canes and causes less pliability. Keep sealed blocks and bricks
of clay in a cool area, out of direct sunlight. As it will begin to cure at
about 120ºF, do not leave polymer clay in a vehicle on a hot day. If possible,
order clay in bulk during cool months to avoid shipping raw clay in high
temperatures. To eliminate dust and pet hairs from contaminating your polymer
clay surfaces, use plastic wrap to cover work in progress and raw clay if you
need to leave it. Use plastic wrap or sandwich bags to store cane lengths and
unpackaged raw clay. Over time some plastic wraps will interact with polymer
clay; Saran with Cling does not interact and that is what we use to store canes
or cover works in progress. Also, as polymer clay will interact with some hard
plastics, do not store raw clay in plastic containers without wrapping the clay.
Deli-style parchment paper also works well between the sheets of clay as it will
not leach the plasticizers, but waxed paper will cause leaching over time.
Can I add other
things into polymer clays before baking?
Many art supplies can be added to polymer clay to create some very beautiful
effects. Most of them can be used on the surface or worked into the clay.
Pigments and powders can be applied to the surface of textured clay to highlight
the design. Especially effective are Pearl-Ex Powders containing powdered mica.
They are available in a wide range of metallic and reflective colors. When
worked into the clay the powder disperses at first in a localized swirl. Then it
moves throughout the entire mass as you continue to work the clay. The more
translucent the clay, the more powders and other inclusions seem to float.
Opalescent effects can be seen, especially when translucent clays are finished
to a high sheen. Glitter, metal leaf, confetti and fibers can also be used on
the surface or mixed into polymer clays. Embossing powders, alcohol dyes and
stamp ink in both dye and pigment forms are all create interesting effects.
These inclusions are all more apparent with translucent clays. Finding new and
different supplies to add to polymer clay is another opportunity for
experimentation.When working with fine powders wearing a dust mask is highly
recommended, as is working in a draft-free area.
How is polymer clay finished to make it shiny?
Take care when cutting and forming the pieces to avoid fingerprints and other
surface imperfections. Smoothing cane slices under plastic wrap is usually
enough to eliminate a great deal of sanding later. Polymer clay can be sanded
and buffed after baking. This will smooth the surface, and ultimately add a
sheen to the finish. Translucent clays can be made almost transparent with
sanding and buffing, The more translucency in a color the easier it is to buff
it to a high gloss after baking. Cernit, Premo and Kato clays take a shine very
easily, FIMO colors are more matted.
Sanding is best done in water containing a few drops of dish washing detergent
using increasingly finer grit wet-or-dry sandpapers. Buffing can be done by hand
with a rough textured cloth like denim or using a buffing wheel. If dry sanding
use care and a dust mask. When using power buffing tools wear protective
eye-wear and keep long hair and shirt sleeves away from the wheel.
When powders or foils are
used in surface applications a protective coating can be added to the cured
clay. Brushing a thin coating of a liquid clay on the surface of a cured piece
and baking again is one solution. Other protective coatings are available. Use
only water-based products with polymer clay as coatings containing solvents will
react with clay over time making it tacky. Many artists use Rust-Oleum
Varathane, a water based interior polyurethane. The spray version of this
product is compatible with polymer clay; many aerosol finishes will later become
sticky. A high gloss finish can also be formed with Future, an acrylic floor
polish. There are finishing glazes manufactured specifically for polymer clay in
both FIMO and Sculpey formulations. These protective coatings can be applied or
blotted with a make-up sponge for a matte finish.
What kinds of glues
adhere best to polymer clay?
What glue to use with polymer clay depends on the other surface that is
being bonded to the polymer clay. White PVA (PolyVinylAcrylate) glues like SOBO
and Aleene's TackyGlue work very well when bonding clay to wood or paper.
Titebond CyanoAcrylate glue is favored by many artists for attaching metal
findings. Liquid polymer clays can also be used to bond clay to clay or other
plastics. Superglues have a shorter shelf life than white glues and need to be
replaced once or twice a year.
Where can you go to
learn more about polymer clay?
There are many people all around the world using polymer clays and they
share their work and information in many ways, in groups like the International
Polymer Clay Association and the dozens of local guilds that are found all
across America and throughout the world. In addition, there are many on-line
groups and archived resources on the Internet. These include Polymer
Clay Central and its message
board at Delphi.com , Yahoo groups like Clay-Polymer
and Polymer Clay
People, Usenet newsgroups like Rec.Crafts.Polymer-Clay plus many other
groups all across the Internet.
Other important resources for polymer clay information include The
Glass Attic, Polymer Clay Daily
and Polymer Clay Notes. In addition
there are more than 100 books in
publication about all aspects of polymer clay use. Instruction is offered by
many incredible artists throughout the world, and listings for classes can be
found at Polymer Clay Workshops.
Many artists also have instructional dvds for sale
Copyright©1995-2010 Sarajane Helm All rights
are held by the artist
Reproduction without permission is
a violation of copyright law
