Silicone mold making using styrofoam form

[Meka]

Can you please tell me if it is possible to use Styrofoam as the intended shaped mold to create a reusable silicone mold?

[Min]

Hi Meka and welcome to the forum.

Giving this thread a bump, hopefully someone will chime in that has more knowledge of silicone mold making than I do.

[PeterH]

Any help? https://davidneat.wordpress.com/tag/preparing-styrofoam-for-silicone-rubber-covering/

[Bam2015]

Here's a thought, if the styrofoam isn't smooth then the roughness might show up in the mold. But I've only made a few plaster molds, so I'm just guessing. 

Betty

[Jeff Longtin]

Hello Meka, when you say "intended shaped mold" what are you referring to? Do you want to use it as the mold box, and pour silicone into it, or are you intending to actually carve a form out of styrofoam?

I've not used silicone but  have used urethane rubber.  As long as I coat non-porous objects with silicone spray I've had no problem with sticking. 

[Hyn Patty]

I think there are good questions posted here already that need to be answered before we can really help you.  BUT if you mean to use the styrofoam as a secondary shell (mother mold) around your silicone 'skin' then yes, IF it's firm enough and not too bendy you can do that.  You'll need however to shape it very carefully to fit up against your silicone firmly with as few gaps as possible and strap or tape it. 

 I normally use a plaster mother mold over my silicone brush on waste molds for my original oil clay sculptures and then go on to cast a resin waste piece to do final clean up and detailing.  That then can be /block/ molded using pourable silicone or urethane to make my master mold pieces - which are then used for pouring my production plaster molds for slip casting.

Or as said if you want to use a styrofoam cooler or suchlike to POUR silicone into as a block mold you can do that too.  But do a small test first to make sure the rubber of your choice doesn't have a chemical or heat reaction with that kind of foam .  Once silicone is set up it'll be fine but the curing process can melt some kinds of foam and not all 'stryofoams' are the same.  A proper reusable mold box, sized and shaped for each project is safer.  If it melts or eats your foam there could be poisonous gases produced.

 

[Hyn Patty]

On 8/5/2022 at 11:56 AM, PeterH said:

Any help? https://davidneat.wordpress.com/tag/preparing-styrofoam-for-silicone-rubber-covering/

Nice link!  Interesting read - I hadn't used styrofoam with mold making quite like that.  Always more to learn!