To ensure the accuracy of the oven temperature and protect your clay, you may want to purchase an oven thermometer. There are some available that have been designed specifically for polymer clay curing. Do not ever try to microwave your polymer clay.
Sculpey Clay can be baked on a cookie sheet covered with parchment paper or cardstock. Some people like to use ceramic tiles or glass that can serve as both a work and clay baking surface.
It's important to understand how you bake Sculpey clay accurately.
For Original Sculpey, preheat to 275 degrees F (135 C). Bake for 15 minutes per quarter inch of thickness. For example, a piece of 1/2" thickness should be cured for 30 minutes.
For Super Sculpey, preheat to 275 degrees F (135 C). Bake for 15 minutes per quarter inch of thickness. For example, a piece of 1/2" thickness should be cured for 30 minutes.
For Sculpey III, preheat to 275 degrees F (135 C). Bake for 15 minutes per quarter inch of thickness. For example, a piece of 1/2" thickness should be cured for 30 minutes. To test the curing, try pressing the tip of your fingernail into the bottom of your piece after it has cooled; it will leave a mark but will not actually enter the clay.
For Premo! Sculpey, preheat to 275 degrees F (135 C). Bake for 30 minutes per quarter inch of thickness.
Additional Sculpey Baking Instructions
It is suggested that thicker pieces be initially baked for 15 minutes, then another 5 minutes, another 5 minutes, etc. The clay needs at least 15 minutes to cure properly. Strength increases as the baking time increases. Always be certain to first check the oven’s temperature accuracy with an oven thermometer.
If an object has a variance in thicknesses, an armature should be shaped in order to “bulk out” the thick parts – tightly crushed heavyweight aluminum foil is the best material to use. Try to keep all parts of the sculpture of an even thickness of clay. Layering the clay is the best method to avoid cracking and maintain even thickness in a medium or large sculpture.
Construct an approximate form from tightly crushed, oven weight aluminum foil (this can be applied over an armature in larger sculptures). Cover form with a ¼” thick layer of clay. Bake for 15 minutes at 275 degrees F (135 degrees C). Add a second ¼” thick complete layer (like a skin), which can be built up slightly to show contours. Re-bake for 15 minutes at 275 degrees F. Then, apply a third complete layer, adding finishing details, and re-bake for a final 15 minutes at 275 degrees F. Overbaking will cause darkening of the clay, and burning can cause bubbling and darkening.