Creating Naturalistic Backgrounds with Great Stuff Foam

Over the weekend I made 10 naturalistic backgrounds for gecko condo. I do not know of anyone else who made their backgrounds on removable pieces of plastic like I have, but Gecko Condo is all about options and I want to be able to change things around as I need to over the years. Most people just make their backgrounds directly into their tanks, which is fine, but not what I wanted for this.

My main tools/consumables for this portion are:

- GE Silicone II brown caulk
- Great Stuff door and window insulating foam
- Virgin cork
- Coir (eco-earth, shredded coconut fibers)
- wax paper
- left over MDF
- Foam brushes
- Latex gloves

You can use some other caulks but the main thing is that it needs to be 100% silicone and not have any anti-mildew chemicals. If it has any anti-fungal additives it is going to be bad news for the animals and the terrarium if it is bioactive. I believe GE Silicone I is also ok, but brands like DAP are not. You also want to make sure to get this in brown or black because it will hide the yellow foam and some of the coir will show through to the caulk.

For the foam, you want the blue can for door and window. The red can is cheaper but problomatic. the door and window stuff is flexible where the gap filler is hard. The gap filler stuff is prone to shrinking and cracking and it just doesn't work as well for this purpose as the door and window variety.

Coir is something most reptile keepers will know as the branded product eco-earth. It is just shredded coconut fibers and used in a lot of things. You can get it in bricks that need to be dehydrated which is the cheapest option. You can also buy bags of it. Most likely the least expensive place to get it is from a hydroponics store. Actually, you can get a better deal on pretty much all of the substrate additives at a hydroponics store, but that is for another blog post.

Overall, to do these 10 backgrounds I used 8 cans of foam and 7 cans of caulk.

The first thing I did was lightly sand the plastic base so the caulk could get a better grip. I then put a thin layer of caulk over all the backgrounds. Many people say you should do this because it hides the foam from the back and sides of the vivariums viewers. I didn't really care about that since the back is already full of cables and tubes, so I did it mainly because the foam gets a much better grip to the caulk than it does to straight up plastic or glass. This took about 3/4 of a tube of caulk.

The next step is laying down pieces of cork where I would like them and then adding foam to create the backgrounds and hold the cork in place. Several months ago, before I started this project, I picked up 55lbs of virgin cork. I used some of the cork for this project, but even after picking out pieces it looks like I barely made a dent in the box. I'll be saving some when I am done but selling most of the extra.


This is the cork I selected for the backgrounds. I ended up using about 75% of what is in this pile.


This is all of the cork I didn't select. It doesn't look like the box shrank at all.

I also built an adjustable bounding box out of some left over MDF and then wrapped it in wax paper. I did this to cut down on the trimming I would have to do after the foam had set. It also helped save foam so it would stay in the box and expand upwards instead of out. The foam, once set, will not stick to the wax paper and is easily separated from it.

Now you just stick your cork in the box and start spraying foam. You can use the foam to build ledges and caves, and you can carve it some before applying the caulk and coir. Just don't build anything up too much with the fresh foam from the can. If you put too much on it just sinks into itself and then stays uncured in deep pockets. If you carve into these pockets you will just come up on the wet foam that will then start to swell and harden and you have to cut it up again. Wastes foam and time.

Be sure to fill in any gaps on furniture you attach to the back with foam. You don't want any areas large enough where your animal can get into them and you can't get to them. This can cause problems not only when you need to take them out for the vet or show and tell, but also if they lay eggs places you can't get at them.

After spending a bunch of time doing this and then letting it sit over night I had 10 foam backgrounds ready for carving.

Now I needed to trim it all. Some of it I wanted to rip out to make cliffs and cubby holes. Other spots I needed to hollow out to use as foam flower pots. I also had to trim it all flush to the edges of the plastic. this was pretty minimal thanks to the bounding box.

Here are the pieces post carving:

Now that you are done with the foam it is time to caulk it all and apply the coir. I didn't take any pictures for this part because it is very messy and you have to work fast. Be sure to watch the clock, and get a friend to help if you can. Once you start laying down caulk you have 7 minutes to spread it in all of the nooks and crannies and apply the coir. If you go longer than that the coir will not stick, or at least it won't stick well. I did the smaller 8 backgrounds in 2 parts to make sure I had time to work it all and the larger ones in 4.

Don't be stingy here with the caulk. I find it works best to designate your off hand as "caulk hand" and the other for coir. Spread down lines of caulk about a half inch apart then take out a foam brush and smooth it out as best you can in a reasonable amount of time. Then take a finger or two from your caulk hand and rub it all over the foam and caulk, being sure to press caulk into all of the crevices and other places. It works well and is fast. You can then take your other hand and dump generous amounts of coir on top and firmly press it into the caulk. It should stick pretty well, but don't be too eager to shake it off.

I don't think I mentioned it yet, but be sure to wear gloves while you do all of this. You are going to get foam and caulk all over your hands for sure and probably your forearms as well.

Here are the backgrounds after sitting over night with the caulk and coir applied:

I caulked the bottom portions but did apply coir to them when I could help it. that is because the bottom 5 inches are just acting as feet to help hold the backgrounds against the wall. You don't want coir here because it can wick water up from the drainage layer into the top substrate layer and that is bad. Again, getting a little ahead of myself.

That's it! Now you just need to put it in your vivarium:

The backgrounds are just resting against the back for now. I am going to add hot glue to the back to make it more secure, and the hot glue will be easily removable when I need to remove the backgrounds. Between the glue, feet, and 4-5 inches of substrate the backgrounds should stay pressed against the back pretty well.

All that is left to do now is add the substrate layers and plant! I have the plants ordered but am not certain when they will get here. Their shipping is a little delayed waiting for a nice day. Hopefully they will be here soon so I can plant this coming weekend, but it might be another week after that.

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