Molding with Polyurethane Rubber-help/tips please!

Discussion in 'Replica Props' started by tubachris85x, Feb 23, 2012.

  1. tubachris85x

    tubachris85x Master Member RPF PREMIUM MEMBER

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    Getting ready to order supplies I need to mold my helmet (transition mold) so I'm going with the Polyurethane rubber due to cheaper costs...

    So far, here's a list of supplies I will be getting:

    -Polytek 35 brushable rubber
    -2300 mold release
    -Johnson/minnewax sealer
    -Cabosil (thickening agent)

    Mothermold material to be determined...between fiberglass, hydrocal, or a custom resin/polyfiber mix..

    I feel that I have a general understanding of how to proceed with this, but I can't help but feel I'm gonna mess something up.

    In my mind, this is the process I understand:

    1. Seal the clay/sculpt
    2. brush on 2300 release agent (or spray?)
    3. mix first small batch of rubber, apply very thinly across entire surface
    4. repeat step 3 (at least 3-4 times(?))
    5. make a new batch of rubber, add cabosil, to make a key "mowhawk"
    6. let everything cure for a day (or however long is needed)
    7. apply mold release across surface
    8. create shim to go down the center of the sculpt/apply vasaline/mold release
    9. begin one side of mother mold
    10. finish other side of mother mold
    11. drill holes and apply bolts/wing nuts to mother mold before separation.
    12. Remove mother mold shells, make a cut down the "mowhawk" making keys down the center.
    13. remove sculpt, reassemble mold and begin casting

    Is this right? I'm going at this entirely alone (for the most part) for the first time ever. One concern is if I am using a sealer on clay, will that ruin the clay? It's plasticine clay. My last question would be is, should I go with hydrocal or fiberglass? Fiberglass is definitely cheaper, but I have a local supplier for hyrdrocal!

    Thanks!!
     
  2. Eaglewood

    Eaglewood Sr Member

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    Brick in the Yard videos on Youtube or Smooth on videos on Youtube-- cant go wrong.
     
  3. Ozymandius

    Ozymandius Sr Member RPF PREMIUM MEMBER

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    I don't see anything to worry about. You've clearly done your research and have a good grasp of what you need to do.

    The sealer won't effect the clay at all, and the only downside is that you will want to scrape off that outer surface when you are done so you don't have chunks of sealer in your next sculpt. In fact, I've often skipped the sealer for plasticenes and just coated it in mold release. Pulled out of the mold just fine.

    As for mother mold, either one will work just as well. Your major difference is going to be ease of use and weight. If you are going to be slush casting, then you'll want fiberglass. But if you are going to be brushing on your casting material, then hydrocal will work for the waste mold just fine. Just make sure that you reinforce it well with some hemp or burlap.

    Oz
     
  4. Beaker

    Beaker Active Member

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  5. NormanF

    NormanF Master Member RPF PREMIUM MEMBER

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    You might want to make a small test piece to practice with first. Of find something laying around your house that you can try. Better to waste a couple hours on something you don't care about than to make a mistake and damage days/weeks/months of work.
     
  6. PoopaPapaPalps

    PoopaPapaPalps Master Member RPF PREMIUM MEMBER

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    Boy, you ain't kidding.
     
  7. tubachris85x

    tubachris85x Master Member RPF PREMIUM MEMBER

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    You crap! That molding video was just what I needed! Thanks for the links! You guys just saved me money! I have to head down to Miami next weekend for drill so I'll take my Friday morning to stop by this store when I pass through Orlando. Didn't realize the smooth on rubber would be a bit cheaper! Thanks!!

    And Norman, I'll give it a shot, but I'm incredibly strapped for time, and just have a week to do this! Maybe I can remold my Radica game finally...
     

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