Today I was messing around with making some prop hands and tried to fill some latex gloves with greatstuff. The stuff came out kinda thick but then just sort of went flat. the foam was just a pool of nasty smelling brown goo in the glove.
I've had something similar happen to me. But I shook the can.
I think it's because I just simply had too much greatstuff in one area.
I used it to make a cast of a skull using a skull mold I made.
The bottom of the skull cured, but the inside was just a mess of gloop.
It's because the greatstuff needs air to cure, so when the bottom cures, it doesn't allow any air to get inside for the rest of the GS to cure.
I really believe that some cans of Great Stuff are just old and don't work properly. I bought some cans to use on props, shook them the same and one of them inflated much better than the other. I actually found that working with the knock off stuff (I later bought a different brand at Kmart) inflated and dried so much better so for now on I am going with the knock off brand.
When you go to Home Depot, ever notice how they have cases and cases stacked up over your head? I wonder how long it takes them to sell all of that and if it really loses something sitting in a warehouse for many months or years. Next time try a different brand from somewhere else and tell me if I'm right. I hope this helps you.
I used great stuff to fill the gloves on my killer clowns. At first they were soft. But after they cured over night they expanded and got nice and firm. Now a few days later they have shrunk and are wrinkled.
So I am not sure why this happened? But in a way it looks kind of cool and goes well the look of the clown masks.
I agree with EvilEyes, not all cans are going to be good cans.
If it comes out slow and gooey, there's a problem.
Try to take the can back for a replacement.
At 3.50 a can, well that's expensive.
They do get old setting on the shelf.
That air-blockage thing was a big problem for me the other month when I was working at Silo-X. I made some missiles, and used greatstuff as filler to keep the funnels (nose cones) on the PVC pipe (rocket bodies). But the foam remained uncured in the center because I'd sealed off the air. When I came back the next day, the sun beating down on them had reactivated the unfoamed stuff and foamed it, and all my nose cones had popped off. I had to take them off and carve the foam down and reglue the cones on. It's temperamental.
Krough had the right idea. 2-part urethane foam is chemically catalyzed, you don't need all that air getting to it to make it foam and cure. And you can mix up exactly the amount you need, no waste.
Thats right Sickie, spray a little water into what ever you are putting the GS into and a little on it when your done. Not alot though.
Two part foam is the way to go is you can afford it. Seems like I seen it in kits for 50 to 60 bucks for a 5 gal kit where as GS runs about 4bucks a can. There is also off brands of GS too. Great stuff may not be the best way, but it will get you started into using foam.
I found that great stuff has a problem expanding and curing if air gets trapped within the foam. You may notice that any Great Stuff exposed to air cures properly. If you cut it open, you will notice that the foam near the surface is dense. Any foam not close enough to the air remains sticky and traps air bubbles. Even if it cures, you can see when you cut it open that the foam isn't dense at all and is prone to shrinking. Check out this pic: Great Stuff Hand picture by HalloweenZombie - Photobucket
See how much the palm area of the hand shrunk, but the fingers didn't shrink all that much? I fixed this by drilling a few very small holes in the mold that allows air to escape. That allowed the foam in the palm area to become more dense and cure properly.
Thank you all for the great info. I do think that the foam at the wrist dried first traping the foam in the center. I am going to give this another go. I want to get this prop done I have a two headed baby in the wings that I want to start.