Why did my polymer clay bubble?

Polymer clay is a versatile and popular crafting material known for its ability to create intricate designs and detailed projects. However, there are times when unexpected issues can arise during the baking process, such as the formation of bubbles on the surface of the clay. Bubbles can be frustrating, but they can often be prevented by understanding the underlying causes and taking appropriate precautions. In this article, we’ll explore the common reasons why polymer clay may develop bubbles and how to avoid them.

1. Trapped Air

One of the most common causes of bubbles in polymer clay is trapped air. When air is trapped between layers of clay or beneath the surface, it can expand and form bubbles during the baking process. This often occurs when rolling out clay or stacking layers without properly smoothing out the air pockets.

2. Insufficient Conditioning

Polymer clay needs to be thoroughly conditioned to ensure that it is soft, pliable, and free of air bubbles before you begin working with it. If the clay is not properly conditioned, it may contain air pockets that can expand and create bubbles during baking.

3. Moisture or Contaminants

Moisture or contaminants on the surface of the clay can also lead to bubble formation. Water, oils, or residue from hands can create steam or gas as they heat up during baking, causing bubbles to develop.

4. Rapid Temperature Changes

Drastic temperature changes during the baking process can contribute to bubble formation. For example, placing polymer clay in a very hot oven immediately after removing it from a cold workspace can cause air to expand rapidly and form bubbles.

5. Overbaking

Overbaking polymer clay can lead to excessive expansion and bubbling. Follow the manufacturer’s recommended baking time and temperature to prevent overbaking.

Preventing Bubbles

To avoid bubbles in your polymer clay projects, consider the following tips:

  • Thorough Conditioning: Properly condition your clay by kneading it until it is soft, smooth, and free of air pockets.
  • Smooth Surfaces: When stacking layers of clay or covering objects, smooth the clay to eliminate trapped air.
  • Avoid Contaminants: Keep your hands and workspace clean to prevent moisture or contaminants from coming into contact with the clay.
  • Gradual Temperature Changes: Allow the clay to come to room temperature before placing it in a preheated oven to prevent rapid temperature changes.
  • Follow Instructions: Follow the manufacturer’s recommended baking time and temperature for the specific brand of polymer clay you are using.


In conclusion, bubbles in polymer clay can be caused by various factors, including trapped air, insufficient conditioning, moisture or contaminants, rapid temperature changes, and overbaking. By understanding these potential causes and implementing proper techniques and precautions, you can minimize the risk of bubbles and create smooth, flawless polymer clay projects. With practice and attention to detail, you’ll be able to achieve beautiful and bubble-free results in your polymer clay creations.

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