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i wonder if the spray foam greg was talking about in another thread would make a good backing to stiffen up a cured latex mold. put it on before the mold is removed. rosanna

I was hoping someone would pop up and tell us why my harebrained idea wouldn't work. I think your application (backing the latex) would be ideal. IT doesn't require any detail, does not heat up, and would be removable.

I've often wondered how people back up the thin latex, to fill the mold with anything. I Would use the cellophane though, just to assure that the foam doesn't stick to the latex.

Let me know if I need to patent yet another use for the spray foam. OH Important. Do NOT use the latex spray foam. It does not harden as hard as the other.

Greg

i would think that barring undercuts the foam could stay as one with the latex. otherwise a good coating of spray grease would probably work fine. i am putting this idea into my 'to try' file. rosanna

Polyurethane foams like Great Stuff will stick to everything when cured. In thick sections there is some heat generated as they cure.

Whatever you do, don't get it on something you don't want it on. There is no solvent for the cured foam. Wear plastic gloves or you'll wear foam for a week or two.

Ron

The cellophane idea comes from my days as a production potter. We used the foam to fill the spaces in the boxes instead of peanuts. Lay down a foam layer, a cello layer, then pieces, then cello, then foam.

And yes, you are right, it WILL stick to skin, nails, hair etc.

Greg

watershed wrote:I was hoping someone would pop up and tell us why my harebrained idea wouldn't work. I think your application (backing the latex) would be ideal. IT doesn't require any detail, does not heat up, and would be removable.

I've often wondered how people back up the thin latex, to fill the mold with anything. I Would use the cellophane though, just to assure that the foam doesn't stick to the latex.

Let me know if I need to patent yet another use for the spray foam. OH Important. Do NOT use the latex spray foam. It does not harden as hard as the other.

Greg

Greg

I have backed up thin latex with a plaster "mother". Spray foam would probably work.

gotta love that great stuff! one of my fave home repair 'tools'. i used it to repair all the broken asbestos shingles on our house. spray foam, sureform, paint, missing piece be gone. lol. rosanna

Well if you are ever building a waterfall, Great stuff is your best freind.

Greg

One alternative that might work for you and, if your pieces are small enough, not require any reinforcement is silicone caulk. It's cheaper and faster than latex (only need to do one thick coat). I do it outside or in a well-ventilated space w/a respirator b/c it stinks and isn't too healthy, and make sure that you're hands are wet and soapy so you can model it around your master form w/out it sticking everywhere. I learned this from a workshop taught by Stephen Paul Day, and it's worked great in my experience!!

let me know if you give this a try...

take care,
penny

As Bert says plaster is the tradional material used but I have found that after the first layer of silicone for detail I can add more to thicken it so it can stand some on its own. Then I add paster to make sure it will be strong enough. Plaster is cheaper than silicone but can take time.