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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 National Polymer Clay Guild
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. |