Even thickness of silicone in bust?

Sevv

Sr Member

RPF PREMIUM MEMBER

• Sep 30, 2015

• #1

My latest project is a silicone bust. A relatively small matter but something I've only just thought about... could someone please give me some advice on how to achieve an even thickness of silicone on my finished pull?

I have moulded my sculpt in plat sil10 with a fibreglass 2 part shell and intend to cast it in plat sil10 using a release agent. Now normally I'd paint on my silicone with a bit of thixo and try my best to achieve an even thickness. Does anyone have a better way?

I could attempt to rotocast this piece but plat sil10 even in its unthickened state isn't the most free flowing substance in the world, I'm unsure whether it would successfully rotocast.

Anyone have any tips please?

Many Thanks

 

pitchforknumb

Sr Member

• Sep 30, 2015

• #2

The easiest way to get an even thickness when casting silicone is to make up a core for the inside of your mold. Basically you cut 1/4" strips of clay and lay them on the inside of your fiberglass jacket and get the clay as smooth as possible. Then when everything is smooth and even you build up layers of fiberglass, either from epoxy, or polyester, until you get a good solid core. You will need to have some registration points with your outer fiberglass mold for the core to line up correctly though. And then you can do an injection mold, or a pour mold, but that option may be really hard to pull off now since your fiberglass jacket is already finished.

 

Sevv

Sr Member

RPF PREMIUM MEMBER

• Sep 30, 2015

• #3

Thanks for the reply, I did think something like that might be my best option.

Has anyone ever tried thinning your silicone slightly with, for example white spirit, to get that flow and then rotocasting? In my head that should work

 

zorg

Master Member

RPF PREMIUM MEMBER

• Oct 1, 2015

• #4

i thought thinning it down would cause it to shrink when the solvents evaporate out of the silicone.

-z

 

Mr Mold Maker

Master Member

• Oct 1, 2015

• #5

You can try using an actual silicone thinner to lower the viscosity. I don't believe it will make it any easier to slush cast an even thickness. Keep in mind, any solvent you put in will eventually come out, and it can result in a very oily pull, or even in slight shrinkage. It also reduces the shelf life considerably.


A core is by far the simplest and easiest way to go for precise silicone thickness.

You say you're making a bust, correct? Are you planning to backfil it with foam or resin? If so, I'd just recommend laying it in by hand as you've been doing.

 

XtcofPain

Sr Member

• Oct 4, 2015

• #6

If you use White spirit the silicone will shrink after it evaporates. Its a cool trick to use sometimes to shrink something down but the piece can distorte sometimes. Make a core and then drill through the core on the inside. use this with a piece of metal pipe, a drain bomb or a large syringe and inject the silicone through the core. Thats how i do it. You can brush in a detail layer into the mold first if you dont have a degasser and using some retarder with the mix pour from a height in a narrow stream into the syringe and inject.

 

Sevv

Sr Member

RPF PREMIUM MEMBER

• Oct 5, 2015

• #7

Thank you everyone, very helpful advice. Ill go with that method. Cheers