Sculpey III 2 oz - Tranquility. This popular oven bake clay is easy to work with and great for kids. Once cured, Sculpey III bakes hard and takes on a matte, bisque-type finish. It' s easy-to-use and stays soft until you bake it. Bake at 275 F for 15 minutes per 1/4 in (6 mm) thickness.