Polymer clay is comprised of pvc, pigments, binders and filler. The binder is a plasticizer, an oily liquid which evaporates out of the clay during baking to allow the pvc particles to bind together. The plasticizer can settle in the packages of clay during long-term storage, and needs to be mixed back into the clay in order for it to cure properly when baked. “Conditioning” is the process of mixing the plasticizer through the clay, which softens the clay, making it pliable and workable. This can be done in a variety of ways, such as rolling, twisting, and squishing between the fingers; rolling through the pasta machine; chopping through a food processor, or a combination of all of those! (Note: if you use a food processor to condition your clay, you will need to dedicate it to clay and not use it for food.)

The different brands of clay will condition at different rates (I.e., some are softer than others). Sculpey and Sculpey III are the softest, needing very little conditioning. Fimo Soft, Kato Polyclay and Premo are firm at the beginning, but soften fairly easily as they warm. The firmest is Fimo Classic, which usually benefits from the food processor method. Sometimes the clay is so firm that it needs a softening agent– a softer clay or a product called “Mix Quick”.

Warming the clay before conditioning can aid in softening it. Body heat, a heating pad on low, or a bowl of warm water can all be used. Place the unopened package of clay into a ziplock bag, and put it into your pocketor sit on it for about 30 minutes. Alternatively, you can wrap a washcloth around it and place it between the folded sides of a heating pad set to “low”, checking the clay every few mintues to make sure it doesn’t begin to cure, up to about 15 minutes. To use the warm water method, make sure your ziplock bag is watertight and immerse the clay in the warm water for 15 minutes.

While firm clay can sometimes be difficult to work with, the opposite problem is also bound to occur occasionally. “Fresh” clay, that which has recently left the manufacturer, is more susceptible to being exceptionally soft. While this is a good thing in many cases, it can make canes difficult to work with and can cause distortion in Skinner blends. To reduce the amount of plasticizer in polymer clay, you can “leach” it out by using clean printer paper. With a stiff tissue blade, slice the package of polymer clay into 1/8 inch thick slices and roll through the pasta machine. Stack two pieces together and roll again. Repeat until all of the clay has been rolled into a single sheet. Place the sheet between two pieces of clean, white paper. Put two pieces of waxed paper on the outside to form a sandwich or a stack. The wax paper prevents the leached plasticizer from staining other surfaces. Place this stack on the floor or on a bookshelf with a heavy stack of books on top, and leave overnight. (For a quick semi-leaching, sit on the stack for 30 minutes.)