How to Avoid Bubbles In Mold Making

Avoid Bubble Formation in Your Mold



All molds get bubbles. including silicone molds or latex molds. But with ComposiMold mold making it is possible to see the bubbles so you can remove them. This video shows you the process for getting rid of bubbles in your molds.


The reason the bubbles exist can be caused by quite a few different reasons: If your original master part is not sealed correctly, bubbles may come out from the part. This is probably the cause if you are using plaster, clay, or wood as the master. To solve, seal the master first with several layers of polyurethane spray or wood sealers. Elmers-like glue (PVA glue) works well to seal parts. In some cases petroleum jelly can stop the air from escaping your original part and also act as a mold release.


We recommend using Bubble Buster. This reduces bubble formation during mold making by reducing the surface tension so the bubbles rise up and away from the master.


You may have too much mold release, so the interaction causes bubbles. This seems to happens quite a bit when you use a vegetable oil as a mold release, but other mold releases may have this affect. Be sure to wipe off any access.


You may have bubbles in the ComposiMold from bubbling in the microwave. It may be worthwhile to remelt the ComposiMold and let it cool at room temperature so the bubbles can rise to the top and escape.


You may be putting bubbles in when you pour the ComposiMold into the container. The best way to avoid this is to just pour gently into the lowest area of the mold so the ComposiMold rises up over the part. Be sure any holes are filled with the ComposiMold and you are not trapping air.

You can also do quite a few things to get rid of bubbles that are in your mold while the mold is still liquid:

  • You can use a toothpick or other object to push out the bubbles. This works well in small cracks or under undercuts
  • Before sticking the ComposiMold in the freezer to cool, let it sit out for about 10 minutes to let the bubbles rise to the surface.
  • Vibrate the part by pushing on the sides or even better a back massager against the mold sides.
  • You can also paint on a thin layer of ComposiMold over the areas where the bubbles are forming. If you let this cool, you can be sure the bubbles won't be against the master part.