Cracking is almost always caused by insufficient curing or by baking a sculpture with uneven thicknesses throughout. To ensure you have a consistant thickness in your piece, we recommend "bulking out" with foil or creating an  armature from Sculpey® UltraLight™. It is also very important to adhere to proper baking times and temperatures. Using an oven thermometer is the most accurate way to make sure your oven is heated to the exact temperture.

Always use a type of support under the clay if there are raised or extendend portions, as it softens slightly before it hardens in the baking process. Without this support the areas can sag or crack. If the clay is slightly dry, this can also cause cracking. Add some Sculpey® Clay Softener, work in, and the clay will be re-constituted. Because the clays shrink less than 1 percent when baking, this does not lead to cracking except in cases where the layer is extremely thin, such as over a glass vessel. Over time, because of temperature and humidity changes, a crack may occur.