Materials Question re: Expanding Foam

[MiiKwai]

I like sculpting in expanding foam, but as you know it's a bit porous when finished. I want to sculpt a shape in the foam then use that shape as the blank for a silicone mold that will then be used for resin casting, basically replacing clay as the original sculpture with foam. Can do? How can I alter the foam to be mold-makin'-material?

 

[Sinned]

I'm not sure what most people do, but I've had success in the past coating foam with Bondo, and sanding down. But if you have intricate designs, this may cause a lot of headaches.

 

[PoopaPapaPalps]

It's going to be a bit of work no matter what but in place of Bondo, I've used wood glue in the past to seal the foam sculpt. Just build up the layers and sand it down smooth after about a good 3-4 layers laid on.

 

[zorg]

You could use 2 part foam instead of the stuff from cans.

The 2 part has much smaller holes, you can cast the 2 part stuff into blocks and carve from there
i have done this and then a skim of body filler and sand.

You can see the much smoother foam second pic down in this thread
http://www.therpf.com/showthread.php?t=68487