Properties of
Different Clays
Written by Mike Brent
The purpose of this thread is to help newcomers determine what kind of clay
they need to look for. I'll kick things off, and feel free to add anything
else that seems appropriate.
PLASTICENE:
Plasticene is what's generally referrred to as "modeling clay". It's also
known as Plastilena (Italian spelling I think) and I've sometimes seen it
called "plastercine" (Brittish maybe?).
It's an oil-based clay that never hardens. This is the kind used for "claymation".
Actually that's not entirely true, because in most so-called claymation films
most of the bodies of the puppets are actually made from different materials
and only certain parts are made from plasticene, namely those parts the animator
needs to manipulate like the faces and hands.
The Van Aken brand is considered one of the best. They make a line called
Claytoons that comes in a great range of colors and should be available at
many art supply and craft stores. There is also Roma Plastilena, an Italian
clay used by sculptors that comes in varying degrees of hardness but only
in a few colors. Chavant is another manufacturer of plasticene, and also make
varying grades of hardness, but again it's more for sculptors and doesn't
cme in the range of colors a clay animator would need. These clays are good
for making prototypes that will be used for molds.
DO NOT PUT PLASTICENE IN THE OVEN!!! It will only melt into a greasy
puddle and create a fire hazard. People sometimes get mixed up and think all
modeling clays will harden if baked the way polymer clay does, but that's
not true. Read the label... if it doesn't say to bake it, then don't.
POLYMER CLAYS:
These are similar in some respects to plastilene, but once done sculpting
with them, you bake them in the oven and they harden into a plasticlike consistency.
Popular brands are Super Sculpey and Sculpey 3 (stay away from the original
white Sculpey, it's sticky and hard to work with), Sculkpey Premo which is
their premium line, Fimo and Cernit in Europe (I believe both are very hard
and difficult to sculpt with until they've been "conditioned" either by running
through a pasta machine a few times or beating with a club for a while).
People often ask about using a polymer clay to do clay animation with, as
a substitute for plasticene. This is not recommended, because these clays
all require some degree of conditioning prior to working. If you let it sit
overnight and try to bend it the next day, it will crack. The Sculpey line
is softer and requires less conditioning than the European brands, but a pasta
machine ($40.00 or less on ebay) is still recommended, or else get ready to
knead it in your hands for a good while.
EPOXY PUTTIES:
These include Magic Sculpt, Aves Apoxie Sculpt and Apoxie Clay and also there
are some sold at hardware stores for use in plumbing and various household
tasks... one good line being Devcon. Epoxies come in two parts that must be
thoroughly kneaded together to begin the chemical reaction that will result
in their hardening. You CAN mix them in your bare hands, but it's not recommended.
You have to mix for a while, until the color becomes completely even and it
begins to feel soft and warm. A good idea is to wear some rubber gloves, at
least while you're blending it together, or at least have a cup of water handy
so you can clean it off your hands. If it starts to harden on your hands it
will take a few days to pick it all out of your skin, and it doesn't feel
good! After you have it thouroughly mixed, it's a good idea to let it sit
for a few minutes (maybe while washing your hands) and it will solidify a
little... at first it's too soft to work with.
Generally speaking the hardware store varieties will come with an "open time"
or "working time" of anywhere from 5 minutes to maybe 20 minutes, meaning
you have that long to manipulate it and then you need to keave it alone and
let it set up. If you keep working it you'll only mess it up. The artist's
grades, like Magic Sculpt and the Apoxie line give you a longer working time,
maybe up to a few hours. The thing to keep in mind is how long do you need
to work on your sculpt.... if it can be done in an afternoon or in a few minutes,
an epoxy putty will work, but if you need longer then go with a polymer clay.
SULPHER-FREE CLAYS:
Just as an aside, I'll mention a few specialty clays here too. For making
silicone molds you want to use a clay that doesn't have sulpher in it (most
plasticenes do). Chavant makes a brand called Chavant NSP (Non-Sulpherated
Clay), and there's also a brand called Kleen Clay that has no sulpher.
WATER BASED CLAY:
Also sometimes called WED clay (Walter E Disney, who created it for the Disney
studios). This is a fast-drying air dry clay that is used for making maquettes
(rough sculptures to determine pose and details for a more complete work).
Like traditional ceramic clays it must be kept moist by spraying it with water
and covering it with a damp towel and maybe a plastic dropcloth overnight
so it doesn't dry out. It is very soft and works like butter... but I find
it's like working with mud and seems to suck the moisture out of my hands
leaving them feel extrmely dry. I'd say wear rubber gloves or work it with
tools. Wter clay is really not at all suitable for clay animation, but could
be useful for making props or set pieces, or maybe making heads to be used
for silicone molds.
SOURCES:
Here are a few online sources for some of these clays...
The
Compleat Sculptors clay index page
Mr
Art carries the Claytoons range of Van Aken plasticenes and also
Fimo Soft, which is supposed to be a vast improvement over the harder original
formula, more like Super Sculpey in consistency.