Polymer clay is a plastic (polyvinyl chloride [PVC]) mixed with a plasticizer and various coloring agents, fillers, and other materials used to change its color, texture, and working characteristics. It’s available in a nearly limitless range of colors, with a variety of different formulations to serve different artistic purposes. Stored properly, polymer clay can sit for years and still be workable.
Each brand and formulation of clay has its own recommended curing temperature, but most cure between 265° and 275°F (129° and 135°C) for about 15 minutes per ¼ in. (6.5 mm) of thickness. With these low curing temperatures, you can use a toaster oven, convection oven, or your home oven. Always check your clay manufacturer’s recommendations for curing time and temperature.
Although polymer clay is nontoxic, the tools you use with it should be dedicated to non-food use. To cut down on the smell some clays produce when they’re curing (unless it’s burning, this smell is nontoxic), you should tent your piece with aluminum foil, which will also prevent the clay from burning due to potential heat spikes. Don’t use cured polymer for pieces that will come in direct contact with food.
There are three forms of polymer clay currently on the market: Block (or solid), liquid, and paste.
Solid, sculptable modeling clay
Can be softened by adding liquid or paste clay (use the same brand)
Can be stiffened a bit by placing it on paper for a day or so to leach out some of the plasticizer
Must be conditioned before use to make it easier to sculpt and to evenly distribute the plasticizer and additives
Can be textured, sculpted, carved, painted, etc.; Virtually unlimited uses
Commonly used as an adhesive between cured and uncured clay
Can use for image transfers, as a glaze, marbling, you can paint with it, etc.
Most polymer brands offer translucent/clear liquid clay (Kato Polyclay offers colored liquid clay), but some are more transparent than others; experiment to find your favorite.
Can be pigmented with alcohol inks, oil paints, powdered pigments, etc.
Primarily used as a bakeable adhesive to bond cured and uncured clay in any combination
Thicker than liquid clay, and can hold items on a vertical surface
Can be pigmented, like liquid clay
Use to create texture
Currently only available as Kato Poly Paste