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Discussion Starter #1
It's to the point where I need to work on my new tanks' waterfalls. They're made from Great Stuff, as the title says. Can anyone tell me how to get the look of natural stone from carving it? I'm terrible at 3D sculptures and don't even know where to begin. Pictures and/or advice would be appreciated.
 

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I've seen people use that pink styrofoam covered with silicone and then sand to make it look like stone. Otherwise I've never attempted it.
 

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i've coated the pink styrofoam for one of my DIY tanks with epoxy, sand and peat.

Thats why I'm not crazy about Great Stuff. You're better off cutting chunks out and getting a piece of sandpaper to smooth the edges. There is no right way to do it.

BTW: Silicone doesn't truly bond to great stuff. However, if you throw sand, peat, etc. over it while you spray, it will bond efficiently and then you can smear silicone to make it stick better. However, epoxy is the best method that seals out all potential fire retardants that Marcos warns us about. (plus, it hardens like a rock!).
 

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Discussion Starter #4
Thanks, but I'm not using pink styrofoam and I'm not using epoxy. Not this time anyway. I'm using Great Stuff and GE Silicone II. It's a combination that's been in acceptance on this board for years and has seen some spectacular results.
 

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Serated knife is the first thing to say. Could you use some concrete primer instead of silicone? You would be amazed in the length it holds moisture, its coming back to life all over my viv now. Back to the waterfall, just depends on what type of rocks you would like it to look like. Round smooth rocks, large jagged rocks, small jagged. Just get the picture in your head and take your time. I find its easiest to carve by cutting wedge shapes slowly, small pieces at a time so you dont over do it.
 

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A good trick to get a very good bonding of silicone to the foam is to dump peat and sand (sand is probably better) ontop of it ASAP after you spray it. Silicone can be pealed off if you just rough the Great Stuff up alone.

Additionally, do several layers of silicone if needed, and jab the peat and sand mix into the silicone before it dries. It looks nicer, and insures it sticks well without it rubbing off. Jabbing it into the silicone allows for you to come back and put more layers on, without the subsequent layers pealing off (peat becomes weak link).
 

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Rain_Frog said:
BTW: Silicone doesn't truly bond to great stuff. However, if you throw sand, peat, etc. over it while you spray, it will bond efficiently and then you can smear silicone to make it stick better. However, epoxy is the best method that seals out all potential fire retardants that Marcos warns us about. (plus, it hardens like a rock!).
I haven't tried epoxy over the great stuff, but I use Elmer's probond, which is a polyurethane adhesive (like gorrilla glue) and it works real well, since they are both similar compounds (the glue even foams up a little, but gets much harder than the great-stuff)
...But you weren't looking for advice on adhesives, so...

As far as sculting...you must have an idea what you want...you just have to go for it. I've never done an all foam background, but what I have noticed is that the foam looks totally different once it gets coated...some times you'll look at the fresh foam and think :roll: yeah...right! But when it gets coated, sometimes you get surprized at how natural it starts to look.
Good luck!
 
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