Sometimes things don't work out

I decided to make terrain boards for an alien planet, using interlocking foam floor tiles.  These are cheap and easy to cut, seemed like a great material to use.

I cut a crater out of one and also made some smaller rocky depressions, then stuck it on top of another tile.  All good so far.

A couple of coats of paint later, I'm liking the look of it.

Sand gets glued on to add texture.  I'm really liking it, I have visions of dozens of these tiles, with mountains and rivers and anything else I can think up.

At this point I accidentally spilled half a cup of tea over it, creating a very nice lake in the middle.  I did not take a picture of this, being otherwise engaged in mopping it up.  I left it overnight and it seemed to have dried out ok, disaster seemed to have been averted.

Another coat of paint and some drybrushing later, I'm feeling really pleased.

The rocky bits are painted and drybrushed too, and it's good to go. :)

But...

Overnight it warped.  I'm pretty sure this has nothing to do with the tea incident.  I think it must be the glue and paint pulling against the foam, which is very flexible.  I can straighten it, but it cracks when I do.  I have no faith that the jigsaw bits will survive being repeatedly joined and separated. So, this isn't how I'm going to get really nice looking terrain for my space project.

But...

I really like the foam tiles as a material to work with.  I'm going to try using an MDF board as a base and build the tiles up on it.  The jigsaw bits won't work with that, so I need to make the tiles square.  If I cut the jigsaw bits off all sides I lose 2", turning 12" squares into 10" squares.  But by cutting the tile into quarters and reassembling it with the jigsaw pieces all in the middle I only lose 1", so I can make a set of 11" squares, which is good enough for me.