Small bubbles on the surface of my resin casts

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This topic contains 3 replies, has 2 voices, and was last updated by  Katherine Swift 6 months ago.

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  • #26306 Reply


    Hi, I’m using Smooth-On Smooth Cast 300/305 for casting and Mold Max 14NV for my molds. I’ve been getting good results but there are some tiny bubbles on some of the undercut surfaces.

    So today for the first time I tried casting in a pressure pot. The resin I used had 7 min pot life and 30 min cure time. I used around 35-40psi in the chamber. After 30 min I took out the pieces and saw bubbles on the surface of the resin like they were poking into the silicone mold. Someone suggested I make the molds again with vacuum chamber so there are no tiny bubbles inside the silicone. It’s a long process and I don’t have a lot of silicone left. So, is this something you’ve experienced? Any ideas how to get rid of these bubbles on the surface?


  • #26330 Reply

    Katherine Swift

    Hi Sait,

    I’m sorry to hear you are having problems.

    Are you sure you were pressure casting? Bubbles rising to the surface of the casting sounds like vacuum casting.

  • #26365 Reply


    Hi Katherine,

    Yes, I’m very sure 🙂

    • #26372 Reply

      Katherine Swift

      Then they must have come from the silicone mold.

      Did Smooth On offer any advice?

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