When the weather was a bit warmer, I played around with an idea I came across using expanding foam.  Andrew Pieper posted a how-to on making terrain hills from expanding foam insulation spray and it looked easy enough so I decided to give it a go.

The main concept is to get a tub, fill it with sand and use the depression you make in the sand to act as a mold for the foam to fill into.  This concept is essentially sand casting which I’ve more about in metal casting than anything else.  This technique is nice in that you aren’t dealing with any super-heated metals or anything, just hardware store insulation foam.

I dug out my mold in the sand as the tutorial recommended, cut a hole in a backer board piece with wax paper to help make sure the foam doesn’t stick.  Then I started spraying to fill the void and eventually put the board on top and sprayed more into the hole. Concrete paver stones helped keep the board “sealed” to the tub.

After about 36 hours, the foam stopped coming out the hole and everything solidified.  If you look at the bottom of the board, you can see where things didn’t quite seal up and foam ended up leaking out the side a little.

I pulled the board off and revealed a pretty successful cast.

I pulled it off the wax and cutoff the “sprue” piece so it could lay flat.

The bottom is interesting in that warped upward in the drying process.  It makes it easier to sit on a table with uneven terrain since it is so concave.  If it had went the other way, it’d be almost unusable.

At the end of the day, it looks like it worked out well.  The only issue is it looks like the foam didn’t completely fill out the hill.  I didn’t put my hand over the hole like the tutorial recommended so I’ll need to do that next time.  With the small depressions on the main hill face, it almost looks like it should go with my 10mm scale Dropzone Commander game.  It doesn’t look like it’ll have enough flat surface to work with a 28mm game unless it is completely impassable.  Maybe. I’ll have to get some minis on it to see.

One of the nice things about this process is it automatically texturizes the model and seals it.  Foam usually has a bad reaction to the aerosols in spray cans means you usually have to prime is another way.  With the sand forming a protective barrier, priming the outer layer is very easy and there is little to no risk on ruining the foam.

An admittedly poor choice trying to see if 10mm scale would work but it gives you an idea.

28mm can work too but I was pretty nervous with the samurai at the top as it seemed like he could take a tumble at any point.  I’m not sure I want to see what shape he’ll be in after rolling off what is essentially 10 grit sand paper.