A good effort at pressure

I’m still grappling with the problem of bubbles in my castings. The accepted wisdom indicates that you want to set polyurethane castings under pressure so the bubbles become very small. I think the Smooth-on site suggests 60 psi (413 Kia).

Not having anything that holds pressure, and not wanting to spend a lot of money, I took a trip down to the local Sally Ann and came back with a pressure cooker. Now pressure cookers are only supposed to work at a pressure differential of 15 psi or so – far below the recommended 60 psi. I reasoned that for my little castings, maybe 15 psi would be enough.

I circled around Rona and Lordco and came away with some useful fittings, which I plumbed into the lid. Then with a careful eye on the gauge, I started to fill it up.

Yep, the pot was $7 for a reason: the gasket was shot, and the pot didn’t hold air at all! A paper gasket didn’t make a good enough seal either. Back at Lordco, a helpful man sold me a probable-looking tube.

Now the pot holds air just fine, but the lid is permanently attached to the pot. Maybe I should have plumped for a proper pressure vessel after all.

3 thoughts on “A good effort at pressure

  1. Sorry to hear about your misadventures. I made myself a pressure resin casting machine out of a 2.5 gallon paint pot. I think I paid around $50 for it from the local Sears. Well worth the price for years worth of castings.

    Nothing ever seems easy, right? And we call this stuff a hobby why? I hope you can get this solved, and casting.


    1. Thanks Craig. Watching some YouTube videos on the subject, I think I will try the PVC pipe bomb approach. In the meantime, I’m actually having some success with vacuuming out the bubbles.

      1. How are you vacuuming bubbles out of the resin? Are you using a slow setting resin? Curious as I’ve never heard of vacuuming the resin.


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