POLYMER CLAY The "make and bake" clay hardens after baking it in an oven about 15-30 minutes (depending on the size of the project) at 130*C (265*F). After baked, it will completely harden and hold its shape. It can be painted with ink or acrylic paint. It is ideal for sculpture and jewelry making. The clay will require some conditioning as it will be very hard and tough initially. You will need to knead it until it becomes soft and workable, a roller or a pasta machine may be used in softening the clay. Its shelf life is approximately 2 years.