What is Polymer Clay?
Polymer Clay is a modeling material made of microscopic bits of polyvinylchloride (PVC ~ vinyl) held together with a plasticizer. This mixture has a very workable putty like texture.
It comes in a great variety of rich, brilliant colors. Some colors have mica flecks, giving them a metallic look. Some are opaque, while others are quite translucent. Many of the colors are extremely fluorescent, which makes for very exciting effects when viewed in black light. Still other varieties of polymer clay are phosphorescent. They glow in the dark!
Polymer clay is semi-solid paint!
You work it with your hands at room temperature and harden it in a conventional oven at 230--275F. At this temperature, the oily substance that makes the clay soft is evaporated and the tiny bits of PVC fuse into each other, making a hard, yet somewhat flexible, solid material.
Because polymer clay is a new medium in fine art, many people are hesitant about its durability and archival qualities. Items made from this material should last a lifetime and beyond.
The items made from polymer clay are not intended for food use. They are not designed to contain water. They are meant only to be objects of art. If you buy an item and treat it as works of fine art, you will enjoy it for the rest of your life and pass them on for future generations to enjoy.
Polymer is plastic. Isn't plastic cheap?
Plastic is not cheap! As a matter of fact, plastics are the most complex and expensive materials humans have ever made. Glass and ceramic (clay) are nothing but mineral mixtures rich in silica (sand), dug out of the Earth. Now that's cheap! On the other hand, almost every kind of paint, finish, adhesive and many other construction materials are polymer based or polymer enhanced. The value of anything hand made is the human effort and ingenuity that went into it.
Will it fade?
The pigments used to color polymer clay are the same as those used in many other kinds of plastics, fibers and paints. Polymer clay won't fade or change color any more than a painting hanging on your wall.
Will it break if I drop it ?
If you drop a piece of polymer clay onto a hard floor, it might break, just like your fine china or cherished ceramic vase would if dropped. However, polymer clay is somewhat flexible. It might absorb the shock and not get damaged at all. Compared to glass or ceramic of a similar thickness, polymer clay is MUCH stronger and weighs much less.
Will it crack or disintegrate?
If polymer clay is properly hardened, it will last virtually forever. It will be every bit as stable as your vinyl record collection or the PVC water and drain pipes in your house. There are different qualities of polymer clay. The type that I use is formulated to be the strongest and most colorful.
I've seen things made of polymer clay that were sticky!
Lots of people make the mistake of spraying a high gloss finish onto items made of polymer clay. This type of finish will react with the polymer and never dry properly. This leaves a tacky surface that dust and dirt will stick to very easily. Use of a water based polymer hardwood floor finish or other PC finish that is known to be compatible with polymer clay prevents this problem.
All of the above answers courtesy of polymer clay artist James Lehman.