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I bought blocks of the green foam used in fake plant pots. It carves very well, but is it a good base (to be coated with concrete or epoxy) or is it too soft?.

Any suggestions as to which foam is best?
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Mark

Mark who makes the green floral foam you are using?

The reason I ask is the generic green foam most florists use actually contains formaldehyde, but it is polystyrene so it is nearly identical to the pink and blue stuff.

Also the older stuff degraded very badly with time becoming very soft and powdery, and after about 20 yrs it turns to a goop...don't ask.

Aside from that unless you have a cheap source its actually rather expensive but very carve-able.

I would stick to the pink or blue extruded polystyrene, pink being Owens Corning and the blue being the Dow product. Dow does make a green floral foam but I don't know anything other than its a chute off their STYROFOAM line.

With your aptitude towards electronics I would think you can easily DIY up a hot wire knife. With a hot wire knife the limit is endless and so much cleaner.

In the end you don't need finally detailed carving with a grout or epoxy coating as those two products can add a fair amount of texture and detail.

Cleanliness would be my sole reason from avoiding the expanded product.

Of course all of the above is speaking from no practical experience aside from general carpentry work. All of my knowledge steams from research into my own future projects.

Cheers
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Jeremy Payne
JB Reptile

1.0 Snow "Kahl"
0.2 Triple Het Moonglow "Kahl"
0.1 Orange Tail Hypo Het Leopard
0.1 Double Het "Sharp" Snow
1.0 Ghost
0.1 DH Ghost
1.1 "Kahl" Albino
1.0.2 Hypomelenistic
1.3 Pastel Hypo
0.1 Anerthrystic
0.0.2 Normal

1.1 Morelia Clastolepis

Hi Mark,

I think Jeremy hit it pretty squarely. The green works fine (just from internet research) but it's quite expensive compared to the alternatives, which work great (from personal experience).

I like the extruded (pink or blue) stuff best. But expanded (white) stuff can always be had for free in apparently unlimited quantities. I've even used the peanuts layered with expanding foam, to make a bubbly-looking fake limestone. The only downsides to the white are 1) it is less dense (which after grouting & sealing doesn't seem to matter) and 2) its "sawdust" is more copious and static-charged (can be a little annoying).

I've only used knives to carve the foam, but there are lots of DIY videos on making hot-wire tools to cut foam.

As for details of crevices, etc - Jeremy's right, there no need to do that in the foam, they can be achieved nicely by sculpting the grout on rough-carved foam. But I think that's a higher-skill proposition, and also requires more grout (leading to more weight in the end). You can get great outcomes with more control and less time pressure by carving in the foam, you just need to take care to clean excess grout out your crevices with a sculpting tool after 5-10 minutes of setting-up. (That's the start of the same time window you'd be using if you were just sculpting the grout.)

A very useful tip - to get the first coat of grout stuck onto the foam, I strongly recommend first applying a layer of full-thickness concrete bonding agent (the same Elmer's-glue-looking, acrylic copolymer goop you can also mix with the grout for your coats, and which you can also use as a "plasticizing" topcoat). The adhesion of that first grout coat is improved immeasurably with this act. You can apply the grout as soon as you have your "Elmer's" coat on the foam.

You can also use the "Elmer's" between grout coats. This allows thinner-mil grout coats, which aid in maintaining the details you achieved in the foam carving, and reduces the sculpting required in the curing grout.

Cheers,
Jimi

>>I bought blocks of the green foam used in fake plant pots. It carves very well, but is it a good base (to be coated with concrete or epoxy) or is it too soft?.
>>
>>Any suggestions as to which foam is best?
>>-----
>>Mark
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Mark

Writing more based on what I've read than what I've experienced, I would also say that the extruded polystyrene products are the best overall. I also understand that the denser extruded products are better but they tend to be special order and more expensive. Both the "pink" and "blue" varieties come in a few densities each.

The green floral foam is easy to carve because the "cells" are so much larger but this also gives it its soft, spongy feel and also requires more sealer to fill the pores.