Can you use smooth on silicone on hard rubber item?

Discussion in 'Replica Props' started by TylerHam, Dec 5, 2011.

  1. TylerHam

    TylerHam Well-Known Member

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    Hi All -

    I just got a screen used prop in the mail - Its screen used "stunt" actually - and its a kind of cool knife from an OK movie -
    Vague I know, but I want to figure out my question before I say what it is -

    Its hard rubber, and I wanted to make a resin copy - Can I mold it with silicone like smooth on 25/30 ? Do I need a special release?? Will the silicone damage the rubber, etc -

    Thank you so much!

  2. robstyle

    robstyle Master Member

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    Use some mold release and youll be fine. Depending on the finish, I would potentially used petroleum jelly (Vaseline) in place of the mold release. Just apply it lightly with a chip brush then use a heat gun and heat up the coated surface to get it nice and even. This will also give a smooth shiny surface to the pulls from the mold. Keep in mind any release material could have potential damaging effects on the original rubber part pending the rubber itself and/or the paint.
  3. SonOfPumpkinhead

    SonOfPumpkinhead Sr Member

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    It's probably a urethane rubber prop. When it comes to silicone, general rule of thumb is that nothing will stick to silicone BUT silicone. That said, mold release is a good idea. I'd use some 301 spray which is essentially VERY thinned down vaseline in a spray can. Just lightly mist it and that's all you'd need.

    Planning on doing a two part mold? Maybe be the best bet.
  4. Finhead

    Finhead Sr Member

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    Read all the tech on the silicone before you use it as well. Some of the Smooth on silicone will not cure on urethane rubber, you'll end up with a gooy mess if you don't seal it off properly.
  5. TylerHam

    TylerHam Well-Known Member

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    All good info. Thank you! I'm going to the store tomorrow and I'll do a test run. :). Not sure if the item is cool enough to offer here..... Hahaha. I'll see after the test pull
  6. Contec

    Contec Master Member

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    maybe make a mold of it from alginate first and get a copy from another material (plaster of paris ) and then mold the plaster copy with silicone. Then you dont need to be worried that the silicone might stick to it.
  7. kwalsh0000

    kwalsh0000 Sr Member RPF PREMIUM MEMBER

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    As people have said silicone will only stick to silicone but if its a rubber/foam piece and has any paint already damaged then be weary. I cast a hard rubber piece and despite my precautions alot of paint came off aswell.

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