Styrofoam

[has.been]

Some years ago I bought some expanding foam to fill a big crack (in a wall, before you all start making up your own jokes)
Although it says you can clean out the nozzle, I have found that it is a waste of time, so (it being a fine day) I laid  some sheets of newspaper  on the lawn and played with the rest of the can's contents. It comes out the consistency of soft poo.
Like soft poo you really do not want to touch it with your fingers. You can however have great fun poking & prodding it with a stick, or even putting a bit of newspaper on it, then pulling it away.
 
When it is totally dry it can be carved, broken, even  scribed into. Over the period of a month the various shapes sat beside my painting area. Any time I had a bit of paint left over (at the end of a painting session) I thinned it down & painted it onto some bit of  the shapes. Effectively giving the 'turds' an interesting finish. The ones I had scribed into were then based up (onto CDs or thin MDF shapes) as alien monoliths & standing stones. The others became various asteroids for my spaceship games.

As the bits had been formed onto a flat surface (the newspaper on the lawn) the 'underside' was flat & easy to base.

I hope this helps you.

[Hammers]

Oh, yes. Several times. It is quite useful as adhesive and filler for extruded Styrofoam constructions. Bewre, though, a pile of that foam, painted in earth tones will look very much like a pile of human shit.

[PhilB]

I'v e recently been inspired to try my hand at carving styrofoam. Lots of you blokes have been doing it for ages, but hey, a guy's gotta start somewhere.

Here is an example of two types of styrofoam insulation blocks that I picked up at a local DIY shop (here in France, I tried several but found what I wanted at Leroy Merlin). They are 6cm-thick basic styrofoam (similar to the stuff you find in electronics packaging and the like, and 2cm-thick much denser stuff that I assume must be the extruded polystyrene that I hear folks talking about.



Notice the yellowish stuff on top, and the white stuff on the bottom of the pile. Those are the materials I've started working with.

Both are easily cut and carved with a hobby knife - although the 6cm-thick blocks are almost too thick for any of my extendable hobby knives to cut through, even after several goes, since I have to cut at quite an angle to avoid tearing. The denser stuff also takes details a lot better. I was trying to make a table-top version of the Storval Stairs from the Pathfinder adventure path called "Rise of the Runelords"... and had mixed results.



You can see that I used five layers of the denser extruded polystyrene for the stairs, cut more or less regular notched lines to represent stonework, then cut them up a bit to represent aged stonework, and used the rock you see there on the table to add some surface details, and to rough up the other cuts and slots. The denser stuff took the detail well, the less dense white polystyrene (not shown on that photo) didn't take much detail at all. For that reason I think I'll avoid it in future.

Both kinds of polystyrene took paint fairly well. Unlike an earlier project, I made sure to get spraypaint that was advertised as being usable on polystyrene. No troubles at all, though it comes in smaller and more expensive cans, from a craft store, so there is that. On an earlier project, I used standard spraycans, and the paint did eat its way into the polystyrene itself, especially the bits I'd done carving on, but it wasn't an entirely unpleasant effect, since I'd wanted to simulate rough stone.

Once I've got more and better pictures of the finished project, I'll start a new thread with it all here, but since the OP went and asked about it, I thought I'd share what I learnt here.

If you're still unsure where to obtain it, do what I did. Go to your local lumber store, DIY shop or hardware store or whatever you call it in your country, go to the area where they sell bulk supplies to builders, and ask about styrofoam insulation panels. Most of the ones I saw had drywall attached to them, so were no good to me, but I asked again and they pointed me to another bay with the two types I showed you, with no drywall attached. Worked great, and I'll soon be back for more!