Vacuum Seal Bag removes air bubbles from RTV molds & castings

[Anonymous]

Cool!!

I'll definitely try that the next time I'm casting something. Thanks for sharing.

Mike Tennent

[Anonymous]

If you ever tried casting your own parts you know about air bubbles. I was planning on doing some parts casting and I had read that a one fella made a pressure vessel from painters spray equipment. Having experience problems with air bubbles from previous casting adventures, I looked into making a pressure vessel. Making one would be expensive.

While channel surfing on the TV, I came across an "infomercial" for Vacuum Seal Bags. I figured for $20 I'd have vacuum bags I could use around the house if it didn't work for mold making.
Well it works great. You have to put a board or something on top and sides of the mold box to keep the bag from touching the wet RTV.
When I hooked up the bag to the shop vac, those air bubbles came out fast, almost instantly. I kept it under vacuum until the RTV cured.

NOTE: Be sure your master pattern is well attached to the mold base so it will not float in the RTV. I use rubber cement to hold the pattern down. It holds good and is easy to remove.