Re: Air bubbles in polyurethane castings

From: met-l-flo (
Date: Mon Jul 27 1998 - 15:45:00 EEST


You may want to try to change the orientation of the part in the mold to allow these small bubbles to roll along the surface of the mold and exit before the pot life expires.
This will provide considerable help in a vacuum environment while the air is expanded and can collectively raise to the surface.

Hope this helps,

Carl Dekker

Jack Wittlich wrote:

> Interesting concept "markschanze" writes about here.
> >From: "markschanze" <>
> >To: "RP mail list" <>
> >Subject: Re; Air bubbles in polyurethane castings
> >
> >In slow cure resin systems this will actually drive the air from the resin
> >and into the silicone mold where it dissipates into the pressurized
> >atmosphere.
> I guess this wouldn't work with aluminum molds. I always thought the pressure simply reduced the bubbles until the urethane cured.
> My bubbles always appear on the top surface of the urethane, as if they are searching for a way out. Excessive venting makes an ugly casting, but sometimes fixes the problem.
> Regards,
> Jack
> For more information about the rp-ml, see

For more information about the rp-ml, see

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