[Terrain] Blueboard

I was carving rock columns (.5"x.5"x4") from some spare blue board. The razor
which wasn't all that sharp so it occasionally tore the foam instead of
cutting it, leaving a texture I wasnt happy with. Didn't have any plaster
handy (and I'm to lazy to use sandpaper) so I decided to lightly spray them
and let the spray propellant eat a layer of styrofoam, see what that did to
the texture. On the original flat surface, it gave a dimpled effect; on the
parts I carved, it gave more of a bumpy texture. It didn't eat nearly as much
as it would have if it'd been the white
styrofoam--presumably due to the different cell structure.  The effect
varied a bit with different amounts of spray. Good rock texture, quick and
easy--give it a try.

Sort off OT, but as I'm in the midst of trying a crazy idea for transportable
mountains, most welcome.

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so I decided to lightly spray them and let the spray propellant eat a layer of
styrofoam...
***

As in paint? It's the solvent in the paint that 'eats', right?

I've noticed the effect before, and have been firmly told not to spray with
anything other than water-soluble paint, though I'm thinking the solvent
does nice things as you say. However, do successive coats still 'eat', or do
the layers of dry paint tend to protect? Also, isn't the melted layer more
brittle and likely to damage if dropped on? Speaking of which...

***
from some spare blue board
***

I'd be happy if I could find blue board, though what I'd REALLY like is brown.
Something embarassing about getting a ding in a hill, only to see bright pink.

The_Beast