Is it possible to shrink RTV rubber molds?

A rescent post asked if it was possible to enlarge a prop. I was wondering if the opposite could be done? I've heard of this technique before but does anybody have any idea of how this can be achieved? Especially shrinking RTV rubber molds.

Radiant777

no

http://87thscale.proboards23.com/index.cgi?board=workbench&action=display&thread=1135&page=1

No need to shrink the mold when your casting does it on its own

quote=radiant777;560256]A rescent post asked if it was possible to enlarge a prop. I was wondering if the opposite could be done? I've heard of this technique before but does anybody have any idea of how this can be achieved? Especially shrinking RTV rubber molds.

Radiant777[/quote]

You guys keep saying molds.


It's the casting that you should do this too. That way if you mess it up, you can attempt it again and again.

Yes you can reduce the size of a silicone casting. You mix the silicone with your choice of any of these solvents.

Naptha, Xylene, Toluene, Mineral Spirits.

Measure your solvent addition by volume- not weight

10% reduction= 9 parts silicone to 1 part solvent
20% reduction= 4 parts silicone to 1 part solvent
25% reduction= 3 parts silicone to 1 part solvent
33% reduction= 2 parts silicone to 1 part solvent
50% reduction= 1 part silicone to 1 part solvent
66% reduction= 1 part silicone to 2 parts solvent
75% reduction= 1 part silicone to 3 parts solvent

You mix your silicone base and catalyst up like normal, then you add in the exact measure of volume of solvent you desire for your shrink rate to this silicone mix. Mix it well!

Then you pour this silicone solvent mix into your mold.


You demold it when the silicone cures, and you allow the chemical solvent to evaporate. The silicone cast shrinks as the solvent evaporates.

If you make a silicone mold off of this silicone part. You have to wash it well with dish soap, and coat it in a wax release spray.

Drying the pulled silicone/solvent part in the sun will increase the shrink rate, and just like the grow method- Certain areas will take a lot longer to shrink depending on the thickness.