Polymer clay doesn't dry; it hardens through a baking process. Exposure to heat initiates a chemical reaction, solidifying the clay permanently.
Unlike air-dry clay, polymer clay remains pliable indefinitely at room temperature. It won't harden or shrink simply by being left out. The transformation from soft, workable clay to a firm, durable piece relies entirely on the application of heat, typically in a conventional oven.
The Baking Process
Here's a breakdown of how polymer clay hardens:
- Heat Activation: Polymer clay contains PVC particles and a liquid plasticizer. When heated, the plasticizer merges with the PVC, creating a solid, plastic-like material.
- Temperature is Key: Adhering to the manufacturer's recommended temperature is crucial. Under-baking can result in a weak, brittle piece, while over-baking can cause discoloration or burning. Typically, baking temperatures range from 265°F (130°C) to 275°F (135°C). Always consult the packaging of your specific clay brand.
- No Air Drying: Leaving polymer clay out in the open will not cause it to harden. It will remain in its original, workable state until exposed to sufficient heat.
- No Shrinkage: Polymer clay does not shrink during the baking process. This is a major advantage over air-dry clays, which lose moisture and can significantly reduce in size.
- Oven Type: A conventional oven is recommended. While some artists use toaster ovens, precise temperature control can be more challenging, potentially leading to uneven baking or burning.
Key Differences Compared to Air Dry Clay
| Feature | Polymer Clay | Air Dry Clay |
|---|---|---|
| Hardening Method | Baking with heat | Air drying |
| Shrinkage | No shrinkage | Shrinkage occurs |
| Hardening Time | Varies with size and temperature | Varies with thickness and humidity |
| Shelf Life | Long (unbaked) | Short (unbaked) |
Polymer clay needs to be baked at the correct temperature for the correct amount of time to become hard. It does not dry.
