Polymer clay will break after baking if it was not cured properly. This are several reasons for that:
- Low temperature during baking.
- The clay was not baked for long enough.
- Variations in thickness throughout the design.
To find the perfect temperature for baking polymer clay, we recommend baking test pieces at several temperature / time intervals.
After the pieces are baked and cooled, use the “bend or snap method”:
- If you can bend polymer clay without breaking, it was cured properly.
- If you can’t flex your project without it snapping, it is under-baked or under-cured.
Thin polymer clay will be more flexible than thick pieces. The point here is to make sure that the clay does not snap when you bend clay with your fingers. Do not expect your thick polymer clay to bend in half.
If you are creating a project with clay pieces with varying thickness (e.g. thin at the edges, thick in the middle), you will need to bake pieces several time to ensure that thicker parts are cured properly. Bake bigger pieces first, add more details and bake everything again.