# Waterproof Foam?



## prototyp3 (Dec 5, 2007)

So I dug through the archives searching for how to waterproof foam for aquarium use. I see that most people just cover it by smearing on black silicone sealant, or coat it with layers of concrete. I'd prefer to do neither. Reason being I want to hand paint the exact forms I carve. (concrete will fill in grooves and cover up details)

Any ideas or product recommendations?

I'm really anxious to get started on the project after doing a quick test with Great Stuff. It's a pleasure to carve. Except for the volcano that erupted on me, right in the center. I guess the inside wasn't quite cured. Note for future use: use a structure underneath so foam isn't so thick!
Here's a picture of some test carving. (I slapped a flat grey color over the foam in Photoshop) I'm going to be trying to create a few rock cliffs surrounding my 35 hex, half full, waterfall feature, shooting for an enclosed lagoon feel.


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## nokturnalkid (Apr 3, 2007)

how bout this.


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## swylie (May 10, 2007)

What about mixing sand with some kind of glue? Epoxy maybe, or polyurethane of one kind or another. The sand would add a nice texture that wouldn't be as coarse as concrete. You could paint on top of this, and then apply a clearcoat.

People make backgrounds out of all kinds of materials, so it might be worthwhile to search beyond spray foam and see what people have done to finish concrete, fiberglass or styrofoam backgrounds.


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## prototyp3 (Dec 5, 2007)

The black foam would still have the same problem as Great Stuff. As soon as you carve through the outter skin, water can soak in.

I'm wondering if the epoxy with melt away the foam as it goes through it's curing process. I know it gets hot as it does it's business.
Polyurethane is a good idea, I just don't know how to tell if it's chemicals would be hazardous to aquatic life. I'm not sure if it cures to be inert like an expoy does?

On second thought, maybe clear silicone would work. I know it gets a little hazy/whitish with age, but over painted rocks it might not be so noticeable? I'd actually prefer a dull/matte finish.


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## NeonShrimp (Mar 9, 2006)

nokturnalkid said:


> how bout this.


Appreciate the link anyways Sho-nuff!


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## tazcrash69 (Sep 27, 2005)

LOL, funny, I;ve been toying with great stuff (Have to get a pic up), and using a balloon to try and make rocks to coat with cement (make rock forms to coat), and My first rock spouted when I brought it inside. 
While I haven't done this myself yet, I''m really leaning toward using the cement and carving bigger features that I know will fill in. The extra weight should also help keep that thing down! 

Looks good so far, is that in the tank already?


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## prototyp3 (Dec 5, 2007)

It's not in the tank, it's in half the cardboard box the tank shipped in. I just wanted to see how much the foam would expand and practice working with it. I think I might try to line the cardboard with plastic for the final go. Hopefully it will pull off, otherwise I'll cut off the back 1/4 inch. I can't imagine trying to carve it in the tank, that's got to be difficult.

The other idea I might try is clay. Buy a big quantity, and have it fired and glazed at a pottery shop.

Cement just seems so terribly messy. My apartment management is pretty strict about doing projects in the shared basement, and my lady doesn't like me experimenting in the kitchen. Puts me in a tough position of picking the least messy methods.


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## spypet (Sep 15, 2006)

prototyp3 said:


> As soon as you carve through the outter skin (of the cured foam), water can soak in.


can someone else confirm this is true? 
carving cured _foam in a can_ should be avoided?
if water soaks into the foam, so what's the problem?


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## prototyp3 (Dec 5, 2007)

I didn't say carving expanded foam should be avoided. 

But once you break the skin, you open up the porous sponge-like insides. The reason why that isn't ideal, in my opinion, is because that stuff is more fragile and will likely erode. For example, if you scratch the skinned exterior with your fingernail, nothing happens. If you scratch any of the exposed interior sections, you will have small flakes of foam come free. 

As for water soaked foam, I'm guessing it can be problematic. Water won't really circulate through the foam well, and stagnant water should usually be avoided.


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## mistergreen (Dec 9, 2006)

you're fine if you carve the stuff.. It's just epoxy.


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## JFarmer271 (Jan 30, 2008)

I would just use the foam and then put a sealant like silicon over the top of it to eliminate the problem of water getting into it.

Jeremy


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## prototyp3 (Dec 5, 2007)

I hunted down some more information on the foam and thought I'd share the findings regarding it's ability to stay submerged and resist water. From shopmaninc.com:

*Is this foam water resistant?*

"Yes, but with the following caveat. The foams that we sell are considered closed-cell, which means that each cell that makes up the foam structure is completely closed off from surrounding cells which prevents it from acting like a sponge. It is completely safe for this foam to be in contact with water for hours/days/weeks and even months with no adverse effects. However, it should never be submerged in contact with water permanently. Over a period of years the water contact can begin to soften the foam and cause it to lose its closed-cell status. This foam is designed primarily to be used as an insurance policy in case of damage/holes that could cause a vessel to lose buoyancy. Pinhole sized openings would essentially have no effect on the foam since the amount of exposure is so minimal but you should always make repairs as soon as possible to keep the foam effectiveness as good as possible. This will be the case will all after market closed-cell polyurethane foams and even manufacturer installed foams." 

Looks like you definitely need to coat/seal the foam, especially if you're cutting into it and exposing the cells to water.

---

And to add to that, it appears you can use an expoxy resin on Great Stuff foam because it's polyurethane. (Packing foam is said to melt when touched by epoxy) A clear epoxy can go over painted foam just fine. And apparently epoxy is inert after the curing process where it lets out all it's toxic fumes.


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## catfishbum (Feb 27, 2008)

or this

http://www.cichlid-forum.com/articles/diy_aquarium_background.php


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## iverson387 (Oct 23, 2007)

i used great stuff for a cave backround i made and then covered it in a product called drylok. its consistency is like paint but seals well. i have had my backround in the tank for about 4 months now with no fish loss. also i added charcoal concrete coloring to make the drylok darker. ill post up a pic of it now with algae on it looks more realistic. all the holes are individual caves for my cichlid tank and there are pockets with hairgrass and microsword? in them.


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## kasslloyd (May 28, 2007)

its not epoxy, its polyurethane foam... which is what "Great stuff" is. It's 100% waterproof, even if you cut/carve it. It's "closed cell" as in its not a sponge.. Although you are correct it's not exactly the strongest stuff and if you bump it it can break pieces off that will float around. And since its "closed cell" its buoyant, because of all the trapped gases. So you'd have to make sure its well weighted down.


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