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35617Re: [hobbicast] Vacumning a large plastic pour

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  • Chris Bailey
    Dec 1, 2005
      I use a large stainless stock pot with a piece of plexiglass over the top. The plexi has a hole drilled to put the vacuum hose into it. I use vaseline for a "seal" between the rim of the stock pot and the plexi. You have to press the plexi down for 10 -15 seconds after you start the vacuum pump to help it seal but once the vacuum builds up, it's fine.

      Oh for anyone that's interested, I use an old refridgerator compressor for my vacumm pump. Not all work for this but I lucked out and the one I found, does.

      Chris Bailey

      Lyle <creepinogie@...> wrote: Anyone here have experience pouring large amounts of liquid plastic
      into rubber molds? I just made an 18" x 9" x 8" rubber mold split down
      the middle which takes about 32 ozs of plastic (thin wall model) and I
      keep getting little air bubbles as I don't have a vacumn jar large
      enough. I'm using Smooth-On 410 plastic. I've never had this problem
      with their 405 series plastic but selected the 410 for it's shrinkage
      and longer pot life. I'm not sure if I can make some sort of seal over
      the opening in the mold as I need to tilt the mold while pouring the
      plastic and gradually move it to horizontal as the plastic fills it.
      this is because of the shape of the pattern would trap air if I didn't.
      This plastic copy will eventually be a foundry pattern.

      Can I vacumn the plastic before pouring it? I have two vacumn pumps but
      all my chambers are made for small jewelery type stuff. Not large stuff.
      perhaps I should make a large PVC chamber or a 5 gallon bucket?

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