Can you use smooth on silicone on hard rubber item?

[TylerHam]

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!

Tyler

 

[robstyle]

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.

 

[SonOfPumpkinhead]

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.

 

[Finhead]

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.

 

[TylerHam]

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

 

[Contec]

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.

 

[kwalsh0000]

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.