Casting Molds from Foam Props

[PlanetAlexander]

Hey all, new here.

I'm starting to really get into foamsmithing and at some point (when I can afford it), I would like to be making molds for my projects. I have done a bit of research but I can't find much on how to make molds from foam. I have found something called mold putty, but I'm not sure how well it will work with foam. Has anybody got any knowledge of how to make molds from foam props? I'm sure it's been asked heaps but I'm just not finding anything.

Thanks

 

[ZeroSum]

Some resources to get you started:

https://www.smooth-on.com/tutorials/
https://www.brickintheyard.com/pages/video-library
https://www.youtube.com/user/punishedprops/playlists

 

[PlanetAlexander]

Some resources to get you started:

https://www.smooth-on.com/tutorials/
https://www.brickintheyard.com/pages/video-library
https://www.youtube.com/user/punishedprops/playlists

Thanks, I'll check out the Smooth-on and Brick in the Yard tutorials. I actively watch Punished Props, and they said that they'd like to make a tutorial on casting molds from foam props, but as of yet they haven't.

 

[cavx]

You might want to run some tests. I have poured silicone over foam with mixed results. Some peeled right off, and other times it bit in enough to tear the foam. Ideally, you want to seal the foam before attempting any mold making.

 

[OlivierC]

I have never tried myself, but maybe you can try some sealing agent, made to mold porous materials.
Smooth-on has some https://www.smooth-on.com/category/sealers-release-agents/
Like I said, never tried, so I can't guaranty this would work. I would try on a small test before buying 5 gallons of it.

 

[PropReplicator2]

Foam is super porous and should be sealed very heavily. No cracks, crevices, or bare foam should be seen or touched by the silicone. This never ended well for me. I’ve been molding and casting things for years and tried foam a few years ago and it didn’t take me very long to end up with a pile of destroyed foam masters, and bad molds. I’ve learned that if you heat seal the foam, and then apply 3-5 layers of plasti dip (allow each layer to dry at least 1 hour between coats!), and let the piece fully dry for a day or two before molding, you should be fine if you are careful with the master and take your time. The key thing is no matter how impatient you may be during the process, and how tempting it is to get it done quickly, you must allow it to dry completely for 24 hours before molding it to ensure that the shell made by the plastidip is fully hardened.