Playing with foam

[Tom Highum]

I remember Sludgemonkey saying that green or blue paints were toxic to frogs though. Had something to do with copper.

[SludgeMunkey]

Aye, green an blue paints should be avoided at all costs. Most of them are made from compounds of copper, cadmium, or cobalt. Many others are made of even more insane chemicals I cannot pronounce. I researched this pretty heavily a while back and so far only Liquitex BASICS acrylic paints in the colors of mars black, titanium white, raw/burnt umber, and raw/burnt sienna are vivaria safe.

While expanding urethane foam is a viable medium for vivaria, there are some very important facts to keep in mind. It does not matter if you use the straw color, the standard color or the black. They are all chemically identical. The real difference is one has a black pigment to make it UV stable, the others just use different mixes of propellants to give different expansion factors.

1. If you make the foam mass too big, it will cure on the outside and remain soft on the inside. This creates two very serious problems- the first being the cured mass is unstable and will crack over time to allow propellant gases from the can to escape. The second is that these propellant gases are toxic in an enclosed environment like a vivarium.

2. Expanding urethane foam is not permanent. Even covering it with paint, concrete, or epoxy, it will degrade in just a few years due to moisture and humidity. The cured foam is also unstable, rapidly expanding and contracting with temperature and barometric pressure.

3. Cure time is the MOST important factor. You must allow the foam to completely cure before painting, carving or coating it. This can take MONTHS even though the foam appears cured to you. Expect freshly carved foam to shrink a bit. I suggest at least a weeks drying time at 75F for about a week in a high humidity environment (like your bathroom or laundry room). Once you carve it, give it at least a week more to stabilize before painting and or coating it.

4. If the foam is used in the presence of water (like a waterfall or pond) even if it is painted it will shrink! If the foam is to be used like this, after it is cured you need to soak it in a bucket of water for a few days and observe it. It may warp into something you do not like.

[John]

I've been fooling around with this foam for about a week - I can see some of Johnny's points in what I've encountered so far, and an experienced friend has also echoed what Johnny has said. If I were making another terrarium I think I wouldn't bother making the background out of any kind of foam, to be honest.

[SludgeMunkey]

Carved styrofoam and acrylic concrete for the win!

[John]

Carved styrofoam and acrylic concrete for the win!

If you're trying to build muscle tone. I would rather just coat one side of a sheet of styrofoam with silicone and peat/coco fibre.