[Azriel]

I just applied my Great Stuff to the background last night, and now I noticed that it has shrunk and peeled off the back wall. I even applied silicone to the back wall beforehand to try and get it to stick better, but that seems not to have helped. It also really warped the egg crate structure that I built for access to the water pump. I'm not sure if that's a problem or not.

So why did this happen and how should I go about fixing it?

Gap in-between the tank wall and the duct for the fan. Should I just fill with new GS?

Huge gap... I can fit my hole hand in the gap. Should I fill that with new GS too I suppose?

Warped the egg crate structure. It won't push or pull back into the proper position, so can I just cut the GS to make it go back in place, and then fill in the cut area with new GS?

What can I do to prevent this from happening again? I only have one can of GS left, and I really don't want to order more. I also don't want to use the regular (yellow) kind I can get in the store.

 

[Bighurt]

GS and glass don't bond well.

Cover the glass with silicone than apply the GS.

 

[Scott]

GS and glass don't bond well.

Cover the glass with silicone than apply the GS.

From his post ...

I even applied silicone to the back wall beforehand to try and get it to stick better, but that seems not to have helped.

 

[Scott]

It's hard to say for sure - but normally the only thing that will cause an issue like you're seeing is too thick of a great stuff coating. You need to put it down in layers if you want a deep covering.

I don't use it that thickly - and I normally poke it a bit while it's curing to make sure that the pressure is being released (so it doesn't pull ... ).

By the way - I've NEVER used silicone on the glass first and I've had no issues.

s

 

[mcaiger53]

I don't use silicone either, and never had any problems. Make sure glass is very clean. Might sound likea silly question, but did you lay surface of tank being done flat? It can be a hassle, but I only do one side at a time, and let it dry for a day before I move it.

 

[Azriel]

I'm a girl.

Yes, the tank was laid flat while I sprayed the GS and for about four hours afterward, but after that four hours I put it back into the upright position. I guess that's where the problem came in. Woops!

Well I can just fill in the gaps now right?

 

[goatdude]

from what it looks like is you used too much gs at one time. then didn't wait the extra time for it to dry and fliped the tank. that made the gs slip and sag making the big hole. next time leave the tank for a few days before moving it. as for fixing it. you can't really fix the big hole. you can try to cover it up with some foam or something. easiest thing to do it pop it off and start again

 

[Azriel]

from what it looks like is you used too much gs at one time. then didn't wait the extra time for it to dry and fliped the tank. that made the gs slip and sag making the big hole. next time leave the tank for a few days before moving it. as for fixing it. you can't really fix the big hole. you can try to cover it up with some foam or something. easiest thing to do it pop it off and start again

Really, are you sure I can't fix it? I don't really want to consider taking the entire background off as an option, because this GS is expensive, and that would be such a waste.

I just finished filling it in with new GS, so we'll see how that works once it dries fully.

 

[mcaiger53]

Filling the hole w more GS will fill it, but if too much is used, I would worry that it would warp your pump box even more. When I apply it really thick, it can take a day or two to fully cure. Even when the top layer is rock hard, the rest is still soft. If I dont like the results, I carve out the spots I'm unhappy with and just redo them.

 

[moose35]

how long did you allow the silicone to cure before adding the great stuff??


moose

 

[goatdude]

what will normaly happen if you fill the hole with gs is 1 of 2 things. either you put too much in and it expands and pushes the rest of the background off the tank and warps the whole background. or you don't put enough in and you have holes. like i said it's easyer to pull the background or get some sheet foam and cover the hole up(then spay foam that). it's not going to easy to fix if you can at all.

 

[jeosbo01]

what will normaly happen if you fill the hole with gs is 1 of 2 things. either you put too much in and it expands and pushes the rest of the background off the tank and warps the whole background. or you don't put enough in and you have holes. like i said it's easyer to pull the background or get some sheet foam and cover the hole up(then spay foam that). it's not going to easy to fix if you can at all.

+1 on this...as much of a hassle as it is, probably gonna be easier in the long run to pull it and start over.

 

[frogface]

The first time I made a background with GS, I was really nervous and only put on a little bit at a time. Worked great. The second time, I figured I was a pro and poured it on, only to have it bubble up and pull off of the glass.

Then I was afraid of GS again and switched to Clay.

 

[Steve88W]

This just happened on my new tank build.

On my last build, I used silicone then spread a nice thick layer of GS foam with no problem.

With this build, I used an old can from the old build without any problems. The new can of GS worked fine at first but over the next two days I noticed significant foam shrinkage. It actually made my first layer of slicone/peat/cocoa mix useless as it just peeled right off. I ended up stabbing the tip of the GS straw into the open gaps between the glass and foam to fill in the voids. This seems to have worked.

 

[D3monic]

I think GS always shrinks up a little bit as it cure (cure time -temp-humidity may be a factor) I have never had it pull of the glass like that. I think it was because of the angle that it was applied around the pump box. If doing multiple sides it is best to let one side dry laying flat and then flip the tank and do one of the other sides.

Thinking back the tanks that didn't shrink where done in teh winter in the garage causing slower cure times VS the tank that did shrink up a little.

I also do not silicone the glass or anything just wipe it clean.

Should be an easy fix just go slow filling in the gap in the back. If needed lay tank flat fill in gap with a little less foam than you think you will need (remember it will expand) and place something moderatly heavy on the background to keep it from getting pushed up. Once its dry you can add a little more if needed or trim anything that may of pushed up out of the gap.

Just be carefull that what ever you use to weight the background down doesnt roll or shift and crack your glass....a good heavy textbook or something would probably work fine

 

[DragonSpirit1185]

This just happened on my new tank build.

On my last build, I used silicone then spread a nice thick layer of GS foam with no problem.

With this build, I used an old can from the old build without any problems. The new can of GS worked fine at first but over the next two days I noticed significant foam shrinkage. It actually made my first layer of slicone/peat/cocoa mix useless as it just peeled right off. I ended up stabbing the tip of the GS straw into the open gaps between the glass and foam to fill in the voids. This seems to have worked.

Id say do this....

How about cutting off the part that isn't sticking and clean the class well and just spray just that area again instead of taking off the whole thing?

 

[Azriel]

Should be an easy fix just go slow filling in the gap in the back. If needed lay tank flat fill in gap with a little less foam than you think you will need (remember it will expand) and place something moderatly heavy on the background to keep it from getting pushed up. Once its dry you can add a little more if needed or trim anything that may of pushed up out of the gap.

This is actually exactly what I did! I just used an 8 lb weight to hold the old GS down and then filled the gap with a little bit of new GS. It's been curing for a couple days now on its side. So far, so good.

Oh and for the person who asked before; I let the silicone cure for a good week at least before I applied the GS.

 

[Azriel]

I think fixing it worked! So far at least. I let it sit for much longer this time, and I just finished getting all the dirt siliconed onto the background to hide the foam. No problems!

 

[iRyan]

The first time I made a background with GS, I was really nervous and only put on a little bit at a time. Worked great. The second time, I figured I was a pro and poured it on, only to have it bubble up and pull off of the glass.

I did exactly this. I had to pull it all off and start again.