# Carving GS foam backgrounds. Any tips?



## ulyssis (Aug 12, 2015)

So I've been carving GS foam backgrounds using a 7" serrated steak knife. Works great when I have lots of room, but when it's time to get into small spaces because of hardscaping items such as wood, stones etc it doesn't work so great. 

What do you guys do in those situations? Do you use any other special tools or techniques?

I got a 24"x18"x36" Exo-terra with a lot of small, hard to reach areas because of wood. I'm dreading the carving stage. 

Also for this build I did something different. I lined the glass walls with egg crate before covering in GS. Hopefully it'll create a tighter bond. My third tank is showing signs of the GS separating from the glass. This is the second tank out of 3, I've built, that this is happening to. I left more than enough time for everything to cure. It only started separating recently after weeks of drying time and a month of grow in. I think after I use up all my GS cans I'm going to steer clear of that method. 

Anyways here's a quick pic of the tank I need to carve:


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## Panther (Feb 23, 2014)

I've found an X-acto/precision knife set to work great! Especially if there is a variety of blade shapes and a couple different length handles.


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## Mavpa (Jan 5, 2015)

I used this little knife from a grocery store pumpkin carving kit. I basically looked like a jigsaw blade on a handle. It was thin enough to bend a few times before it broke, but the kit came with a few... and was $1 after Halloween.


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## MasterOogway (Mar 22, 2011)

Exacto knife set, pumpkin carving set, and for when I'm feeling lazy I use a dremel which also works really well.


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## ulyssis (Aug 12, 2015)

TarantulaGuy said:


> Exacto knife set, pumpkin carving set, and for when I'm feeling lazy I use a dremel which also works really well.



What bit do you put on the Dremel?


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## MasterOogway (Mar 22, 2011)

Any and all of them, pending what kind of carving I'm doing. No real trick to it, pick a bit that looks like it'll do the particular carving you want it to do, and go with it.


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## TheCoop (Oct 24, 2012)

Coarse sandpaper works perfectly ..


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## Judy S (Aug 29, 2010)

so did you silicone the eggcrate, let it set a bit, then spray the GS?


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## ulyssis (Aug 12, 2015)

Judy S said:


> so did you silicone the eggcrate, let it set a bit, then spray the GS?



Yup. Gave it a few days to fully cure.


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## Judy S (Aug 29, 2010)

did you lay it on it's back applying the GS, then when that set up, turn it on a side...wait for it to set, etc.?? It might have had it hold a little better,,,my guess....


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## ulyssis (Aug 12, 2015)

Judy S said:


> did you lay it on it's back applying the GS, then when that set up, turn it on a side...wait for it to set, etc.?? It might have had it hold a little better,,,my guess....



Yeah. What ever side I was working on, that's the side the tank was resting on so gravity worked in our favor. It stayed on that side until cured.


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## Dendro Dave (Aug 2, 2005)

Need to be careful of fumes, but hot knives and other foam cutting tools will work...

https://hotwirefoamfactory.com


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## ulyssis (Aug 12, 2015)

Dendro Dave said:


> Need to be careful of fumes, but hot knives and other foam cutting tools will work...
> 
> https://hotwirefoamfactory.com


Won't using heat create a shiny seal to the foam, much like when the GS dries on it's own? Isn't that one of the reasons to carve foam to get to the dull finish for better adhesion?


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## Dendro Dave (Aug 2, 2005)

ulyssis said:


> Won't using heat create a shiny seal to the foam, much like when the GS dries on it's own? Isn't that one of the reasons to carve foam to get to the dull finish for better adhesion?


Well if using regular colored GS I'd paint it after carving, or cover it in a silicone/peat type mix so that would be a mute point I think, but black waterfall foam is a little shiny even when carved, but as a biofilm and crud builds up that tends to go away.

If memory serves the surface was still rougher then that skin that forms on GS or waterfall foam when it sets, so I think you'd be fine.


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## ulyssis (Aug 12, 2015)

Dendro Dave said:


> Well if using regular colored GS I'd paint it after carving, or cover it in a silicone/peat type mix so that would be a mute point I think, but black waterfall foam is a little shiny even when carved, but as a biofilm and crud builds up that tends to go away.
> 
> 
> 
> If memory serves the surface was still rougher then that skin that forms on GS or waterfall foam when it sets, so I think you'd be fine.



Wait. There is no difference in adhesion between the shiny GS and roughed carved GS?


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## Dendro Dave (Aug 2, 2005)

ulyssis said:


> Wait. There is no difference in adhesion between the shiny GS and roughed carved GS?


I would assume the carved stuff would offer a better surface for adhesion, but It's been a long time since I coated GS with peat or anything... I prefer a rock look. If memory serves though a lot of people don't carve it and just coat it in silicone/peat, and most people who do carve it are planning to paint or coat it in drylock or something like that.


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## wr3ckl1ss (Apr 17, 2015)

Carved definetly has better adhesion than uncarved spray foam I concreted my background (concrete,coco fiber and play sand)my waterfall and aquarium background were completely carved,the background on the land section was not. I've had no issues with my aquarium background or waterfall pulling from the GS or getting cracks,however the uncarved GS requires a thicker layer of concrete doesn't adhere welll and I've had problems with cracking and small sections pulling from the GS if I could redo it I would of avoided being lazy, thinking it would be fine.an taken a couple extra days to carve it cause fixing concrete on a vertical plain sucks.especially when you have to tape off a third of your tank to avoid any falling anywhere else.with my minimal experience I'd still say carved is much better to work with when applying anything to it or even paintining it


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## Encyclia (Aug 23, 2013)

I used one of those retractable knives that you can break along lines when they get dull. I just pushed the whole blade out and carved away. It was really handy having the extra length in some places. I like some of the other suggestions in this thread and will have to try them if I ever do another GS build.

Mark


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## DragonSpirit1185 (Dec 6, 2010)

I use retractable blades and then I got a pack of serrated steak knives at the Dollar Tree and bend them at different angles. They come in a pack of 4 or 5


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## hydrophyte (Jun 5, 2009)

I recommend giving it at least a week to cure. I intoxicated myself pretty good with a bad headache and dizzyness by carving into GS foam two days after application. I detected no odor at all, but there was still something pretty strong coming off it after two days.


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## abIngenui (Oct 14, 2015)

ulyssis said:


> What bit do you put on the Dremel?


I generally use high-speed cutter bits. You can pick up a set of like 10 of them on Amazon for like $10 if you are in the states


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## SLR (Jan 6, 2016)

A cheap fillet knife works pretty good.


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## Ghostkerbomb (Aug 2, 2015)

In tight areas that I can't fit a cheap serrated knife I generally pull the foam apart by hand after using something sharp to puncture the skinned portion. Or a pair of pliers if they fit. You won't get perfect lines if you're trying to carve stone like pieces, but for getting the surface area prepped for some silicone/peat adhesion or similar it works fine, and those tight areas tend to be places where detail carving would not be of questionable value. Alternatively inserting the knife through the foam and using leverage to pop off pieces works and can get cleaner cuts (does that make sense?). There's something satisfying about tearing apart the foam like an animal too

In regards to the foam separating away from the glass, be careful, how is the eggcrate secured to the glass? You may have created a larger problem for yourself because now the GS background can peel away from the glass like it is one big board and the points of contact are smaller because of how it fills each eggcrate square. Especially as you add weight from plants and stuff and it ages over time (as has happened with your other tanks), and it will possibly pull away from the top and work its way down. You may want to run silicone along the boundaries of the GS to give it additional adhesion, or maybe get creative with wood or something to "prop" the background into place securely before it has a chance to separate, reducing the pull of gravity on it

Great stuff is a fantastic product, you shouldn't abandon it, but it works better to fill spots in backgrounds and join separate background pieces imo than as a stand alone background


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