Polymer clay should be stored out of direct sunlight, at room temperature.

Depending on how you plan to use your clay, you may choose to do one of the following:

• Clay dedicated for canes may be quite soft fresh out of the package, and leaching would be recommended. Open the clay package, and leaving the wrapper under the clay to protect the surface underneath, place the clay in your storage area. Cover loosely with plastic wrap to prevent dust from accumulating on the clay and leave the clay exposed to the air for a week or two.
• Conditioned clay that isn’t dedicated for canes can be stored in flexible, semi-opaque storage boxes such as Plano fishing tackle boxes. (The completely clear storage boxes are not recommended as the plasticizer in the clay will cause a reaction in the clear plastic). Gladware or Ziplock containers work well as inexpensive clay storage containers. Ziplock bags also work.
• Plastic wrap can be used to protect conditioned clay from dust, animal hair, and dirt. A clay-compatible plastic wrap such as Saran Cling Plus works well even over long-term storage to protect clay from contamination. It also is very useful for keeping clays from sticking to one another. Raw clay can be somewhat sticky and when trying to separate two pieces of clay, the clay might possibly pull bits from each other as they separate. In the case of canes, this could be disastrous and could ruin the canes.
• Freezing your clay is not recommended as a long-term storage solution. For longer than a day or two, freezing your clay could cause the clay to sweat when you take it out of the freezer. This moisture in the clay could potentially cause problems later during baking, such as bubbling and plaquing (discolorations underneath the surface of the clay, particularly on translucent colors).