How to Degas Silicone in a Vacuum Chamber for Mould Making

Degassing Silicone in a Vacuum Chamber for Moulds

Air bubbles trapped in silicone rubber can compromise the quality of your moulds for resin statues or other detailed castings. Using a vacuum chamber to degas silicone is a practical step that helps achieve professional, air-free moulds, especially when high detail is required.

Why Degassing Silicone Matters

When mixing silicone rubber, air can easily become trapped in the mixture, leading to bubbles that may spoil fine details. If your project demands moulds with crisp surface definition—such as reproducing small statues, jewellery, or intricate patterns—removing these bubbles becomes crucial. Degassing helps to ensure a cleaner cast and prolongs the lifespan of your silicone moulds.

How to Degas Silicone Step-by-Step

After thoroughly mixing your silicone and catalyst (often a 1:1 ratio), pour the mixture into a container suitable for your vacuum chamber.
Place the container inside the vacuum chamber. Start the vacuum pump and watch as bubbles begin to expand and rise to the surface.
Continue the vacuum cycle until bubble formation slows significantly (usually a few minutes, but check your silicone’s pot life and manufacturer’s guidance).
Release the vacuum slowly and use the degassed silicone promptly to fill your mould formwork before curing begins.

Translucent silicones like Pure Mould allow you to monitor bubbles visually during this process, making it easier to judge readiness.

When Should You Use a Vacuum Chamber?

A vacuum chamber is especially recommended for:

Moulds with fine undercuts or delicate detail
Deep or complex shapes prone to hidden air pockets
Critical production where repeatability and mould life are important

For simpler, less detailed objects, or where minor bubbles are not a concern, degassing may be optional but still beneficial for consistency.

Related guides

How To Make Resin Statues

Careful degassing takes your mould making results from hobby-grade to professional. For a complete guide on creating resin statues with crisp details every time, see our main guide on how to make resin statues.