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degassing pump, how much cfm? Answered

I'm looking at a Harbor Freight vacuum pump to degas these liquids before they cure. How much cfm do I need to degas without sucking all the liquid out of the mold?

Thank you for this wonderful Instructable class!

Tony & Kathy Griffin


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Paige Russell
Paige Russell

Best Answer 3 years ago


I'm so glad you're enjoying the class!

A vacuum pump's job is to remove all the air from the degassing chamber, which in turn draws the air bubbles out of the mold material in preparation for pouring it into the mold. While RTV silicone rubber will expand up to 3 times it's size while being degassed, if you're mixing it in a large enough container, there is no danger of the mold material being sucked out of it's mixing container! :)

Harbor Freight's 3 CFM Two Stage vacuum pump will do a great job!

And here's a thorough instructable on how to make your own vacuum chamber:


Happy making!