Pouring Resin - Without Air Bubbles

Resin's Curse - The Air Bubble

When you start casting resin, your initial excitement about the newly discovered modeling technique may be torpedoed by a seemingly unavoidable problem : air bubbles !

When you cast the liquid resin, small airbubbles form inside the mold. Like the bubbles in a glass of champagne, they try to float to the top of the liquid. But when resin gets hard, these trapped air bubbles become tiny holes, like the holes in cheese.

Professional resin companies avoid this by placing the freshly casted resin in a vacuum device. The vacuum sucks out the bubbles. Once the resin is hard, air is allowed back in, and there's not a single bubble left.

Since you and I don't have the space, the technology, the money and the experience to mess around with vacuum machines, we need to try other ways.

There IS a way to cast resin under room conditions. It takes a bit of fidgetting, but you soon get the hang of it and the results are crisp and bubble-free. I'll try to explain step-by-step.

Since Matrix posted a mail about problems with air bubbles when casting a 1/35 helmet, I take the helmet as an example.

About the Author

About Jan (GeneralFailure)

I live in Belgium, Europe. Though modeling was big on my list of hobbies, I spent all my time refurbishing the home we bought a few years ago. I promised I'd be back some day. That day can't be far off, now.


This is good stuff. Thanks for posting it.
NOV 05, 2003 - 08:24 AM
Jan... good article. As a fellow "Cast-a-holic", i find that in addition to painting a thin layer of Silicon onto the object when creating the mold, it also helps to place the wet RTV and the container on top of your clothes dryer. Throw in a tennis shoe or several towels, and let them spin for about 10 minutes. The vibration of the thumping dryer helps dislodge even the smallest bubbles, delivering a super-clean mold to start with. Before pouring the resin into the new mold, I first pour in a thin batch of plaster of paris...this is much cheaper than resin for testing purposes, and will serve the same purpose to help you find where air pockets develop.
NOV 05, 2003 - 07:32 PM
ZerO-CoOl suggested to place a drill on the tabletop to create such vibrations. i now use the compressor (airbrush) on the tabletop. That vibrates the air bubbles straght out. Of course, this only works if you have these "evacuation canals" installed to let the bubbles escape.
NOV 06, 2003 - 01:22 AM
good tech tips. Slight correction - don't use a vaccum to get resin bubbles out, as you decrease the air pressure, that will actually allow the bubble to get bigger! A pressure pot gives great results for the resin pouring stage of casting - the incresed air pressure shrinks the bubbles down to mere pin pricks.
NOV 07, 2003 - 06:21 AM
Vacuum doesn't only make the bubble bigger : it s u c k s the bubble out of the resin. This is still the most used technique by professional resin casters. Pressure pot works well, too.
NOV 08, 2003 - 12:47 AM