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Polymer clay is a modelling material, primarily composed of plastic components. It's a favorite for hobbyists and artists who want to make small scale sculptures, beads, jewelry, dolls, miniatures and such. Brand names include Fimo, Cernit, Modello, Sculpey, Promat, Friendly Clay...
It's popularity is generally due to its ease in preparing and manipulating (it requires no special or expensive tools or materials), its broad range of colors and color potential (it mixes like paint), and its ease in finishing (baking at low temps for hardening). It can also be made to mimic many other materials such as bone, semi-precious stones such as jade, turquoise, etc.
After it's baked, polymer clay can be treated like wood. It can be sanded, buffed, painted, carved, drilled, glued, etc.
It is also relatively inexpensive. Probably it biggest drawback is it's availability. You can't dig it up out of the ground like earth clay. It isn't particulary strong, but it is somewhat flexible. It's best considered for decorative purposes.
Due to some artistic pioneers and the media, polymer clay has recently become very popular in the US among personal adornment artists and crafters. Through a construction technique called canework (millefiori), people can produce and easily reproduce beautiful intricate colorful patterns that can be applied to almost surface.
Chemically, polymer clay consists of microscopic plastic particles embedded in a grease-like base. Each manufacturer has their own set of formulas and dyes, but all the products are essentially the same. Once the polymer clay reaches the proper temperature, the plastic particles irreversibly expand and fuse with one another. However, the mass nor the color of the material changes dramatically. In other words, what you see before baking is very close to what you see after baking.
Because it is not a water-based compound, polymer clay won't dry out when exposed to air. It is very sensitive to ultraviolet rays and temperature, however. Once put inside a properly heated oven, a piece of polymer clay, say the size of a pea pod or green bean, need only bake for about 20-30 minutes before it is done. However, it can also start that baking process while sitting in a car on a bright sunny day.
If you want to know more, may I suggest putting every sigle ounce(gram) of effort into acquiring the book "The New Clay" by Nan Roche. That book pretty much says it all.
DigitallyDo > nitelites