# Great Stuff Foam Background-Failure?? Please Help!



## skier217 (Sep 7, 2014)

Hi guys,
So two nights ago, I tried to do a great stuff foam background on my terrarium. I had already siliconed pieces of wood to the glass. One of the cans came out really thin (looking REALLY bad) and the rest came out normally. I was hoping that the NEHERP background texture mix would cover up the terrible strands of great stuff. After applying the silicon/dirt, I pointed a fan at the terrarium to try to get it to dry faster/smell less. This morning, I vacuumed everything off and it looked awful. You could still see the terrible part of the great stuff, and the silicon barely stuck to it. Now, I just smeared a little bit more silicon, and basically did the exact same thing to try and fix it. Is there anything that I can do to fix these problems? 
Thanks.


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## toostrange (Sep 19, 2013)

I've always had issues with silicone sticking to the cured great stuff. I've either tried off top layer or at least sanded it.


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## skier217 (Sep 7, 2014)

OK. So should I just let this set of silicon dry, then maybe sand all the great stuff down to restart??

Because as of right now, the great stuff foam literally looks like dog poop.


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## rvsur (Dec 13, 2010)

I'm not the most experienced on the matter, but what I usually do is allow the Great Stuff to cure, then I carve it down by taking a straight raiser and removing the outer "shell". I find the silicone sticks better to the freshly exposed surface than the shell. 

And since I'm also terrible with getting a nice even layer of Great Stuff (I always get annoying empty pockets that become exposed after shaving because I rushed), I cake on the silicone. On my latest tank, I did one thin layer to try and hide the Great Stuff, and then I took a foam brush and put a nice thick layer of silicone over it to try and fill in some of the bubbles. This seemed to work pretty well.

TLDR: buy a pack of razors for like a $1.50 and get carving, its tedious and it sucks, especially when trying to get into hard to reach places or working at weird angles, but you'll be much happier with the results.

Good Luck!


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## ZookeeperDoug (Jun 5, 2011)

You'll definitly want to carve away the smooth shell of great stuff to get a good surface for the silicone to adhere to.

My favorite tool is a good ol serrated steak knife and a pairing knife for detail work.


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## tongo (Jul 29, 2007)

In the parts you can't reach just rub some sand paper to roughen it up a bit.


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## planted-tnk-guy (Mar 9, 2014)

Cutco bread knives are amazing too my favorite is the bread knife lol. I have faith you will figure out how to make it look good the first times the learning curve. You can always cut it out and re-foam if it turns out bad. Have fun and keep chiseling away.


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## ngeno626 (Nov 14, 2013)

Also try use a extra thick layer of silicone. it will grab more media rather then a thin layer. I've gotten away from great stuff and only use cork and tree fern now you may want to try something like that with GS as well


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## amandakathryn (Jan 1, 2014)

I just put the put the GS in anywhere I want it to be and then I carve/sand it to the shape I want it with a dremel. It isnt really going to make nice shapes right out of the can you have to carve it. Plus the silicone does not stick well to any g/s that is not sanded.


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## dam630 (Dec 11, 2009)

Sounds like you used an expired can of Great Stuff. Yes, there is a date on every can.
Other than that the suggestions above are all good.
Get to carving out some of the Great Stuff (or all of the "bad" ) and apply again.
Make sure can is new and allow to cure for a couple days, then remove the outer "shell" surface. This gives the silicone a rougher surface to adhere to.
By the way... when estimating how much silicone, triple it !


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## frogpecker (Mar 20, 2013)

All suggestions are good. And I also suspect your GS can had drawn air or has been old/expired.

If you want to invest buy a Dremel tool and carve/sand the GS surface. Goes really fast.


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## Samuraizr0 (Feb 5, 2015)

I used. Great stuff to make my background and it came out awesome. I didn't use wood thought. I used plexi glass and cut it to the needed size. Then great stuffed all over it. Then took a serrated knife to cut away the excess. This way the edges were square and neat


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## Psybahchick (Jun 15, 2014)

I have also had some trouble with the same silicone/NEHerp background mix sticking to my great stuff. The first tank I did, I didn't shave it down or rough it up. I used silicone and it stuck to the majority of the background but there were still quite a few bald spots. For those I used Titebond III made a slurry with the background stuff and stuck it on where ever there was a bald spot. It takes longer to dry and it dries harder but it worked on top of places that had some dried silicone already. However my most recent build I used silicone and the same background mix but applied it on carved GS and it worked beautifully. I generously applied the silicone in sections and I loaded on the mix making sure I wore gloves and pressed it down into the silicone real good. I've learned quickly that it's all about trial and error when perfecting your building techniques and I've also learned there are quite a few options to create gorgeous frog safe setups.


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## Erikb3113 (Oct 1, 2008)

In 5 grown in tanks, i have MAAYBE 1sq ft of visible background left. Almost wish id spent less time forming them.... Just a thought


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## Samuraizr0 (Feb 5, 2015)

well what ever you do don't try my previous post's advise.lol I was so wrong. after some research I found that plexiglass is no bueno! SO instead I just great stuffed it to the back of the glass. you can always great sruff over great stuff too. this may help\


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