using great stuff

[Statman]

Im experimenting in using great stuff to make a half water/ half land setup. I made my initial land area with it, and as I assumed it is super bioyant. But its wayyy more so than I thought it would be. I had rocks piled an it an it just dumped them right off. Is siliconing this stuff in place the only way to hold it in?

[Vicious_Fish]

Got any pics? I would do like you mentioned and try to silicon the rocks into place.

[Statman]

I was going to make my structures with cardboard and then blast them with great stuff an then just peel the card board off when it cured. Well I peeled the cardboard off today, went to work, and when I came home the have warped quite a bit. Is that common? Is my cardboard template ideal not going to work?

[Dr. Awkward]

You are going through the exact same thing I just did with Great Stuff. Yeah, cardboard warping is normal. I even wrapped my cardboard mold several times with heavy duty packing tape and it still warped. And yeah, the stuff floats and you can't hold it down with silicone or weigh it down with rocks. The only think I could figure out is to attach what you already made to the tank with more Great Stuff. It will attach to the glass really well and you can remove it later with a razor blade. Just make sure not to get the Great Stuff on the silicone seams or it will rip them out, too.

[Statman]

Am I just kinda screwed then on the stuff warping? Its gonna happen regardless? And is it going to continue to warp while its in the tank? ANy ideas?

[mellowvision]

great stuff can't really be used in a structural way. it needs to be used more like meat on the bones, if you know what I mean, and you're best off then sealing it with silicone to keep it's integrity.

[cam191919]

it wont continue to warp, it warps while curing

[looney417]

can't you just saran wrap...(not wrap but...layer) the inside the tank, and spray it inside the tank...when you're done you should be able to twist it around and peal it off. as for the top..have fun with an exacto knife?

[looney417]

oh....never mind i get what your problems are. :)

[Vicious_Fish]

I use 1/2" sheet insulation foam for the skeleton of my backgrounds. You can carve it how you want it and the Great Stuff sticks to it really well.

[sCeRaXn]

Ive done three tanks with Great Stuff, and i havent had any of the problems mentioned except warping. The first one i did was with a cardboard template and it warped, then i used a stronger cardboard and let the GS cure for 48-72hrs and it didnt warp. Also, you can definitely silicone it down. Thats how all of mine have been held in place. Just use alot of silicone and make sure to "set" it first by siliconing it into place, then removing it to allow the silicone to set a little on both the tank and the rock. Let it set for 15 minutes or so then place it back where you had it. Weigh it down for 24hrs while the silicone is curing and youll be good to go. When fully cured GS will be as structurally sound as a closed cell styrofoam. The stuff gets pretty hard.

BTW-Check out my thread on the Paludarium i built for my Whites Tree Frog. Thats a mix of closed cell styro and GS and i havent had any of the problems mentioned above with it.

[Sploke]

Will great stuff eventually act like a sponge and become waterlogged, or is it completely closed-cell when dry?

[sCeRaXn]

Im not sure because i always seal mine with something, but im sure itll be completely waterproof. As far as i know its closed cell when cured. Ive never had uncoated GS in water before so i dont know for sure...others will probable be able to help you better.