I’m building my sons proton pack out of insulation foam, and running into issues.
the edges are jagged and I wanted to put some “putty” or filler on it to smooth it out. I had this bondo glazing stuff that I thought would work. I tested it and it of course ate through the foam. It can be fixed, but I need something else as this stuff isn’t gonna do it.
Wood Putty,try that.
Wood Putty shouldn’t eat the foam.
You could also try acrylic caulk, it’s thick and spreadable and shouldn’t dissolve the foam. Can’t really sand it much though so you’d have to work it out to a pretty smooth spread.
FYI don’t spraypaint foam, expanded or extruded, spray paint is not a friend to foam. Instead use a liquid acrylic craft paint or latex paint. Basically don’t use anything with a solvent in it.
coat your foam pieces in wood glue then bondo just fine. Check out my build thread. I did it to my cyclotron. If your edges are jagged, sand them with rough grit paper and work your way up to higher until its smooth.
Wood putty will work perfectly. I prefer elmer’s from walmart, because I like the texture, and you can add water to make it creamier if you choose.
Here’s what it looks like:
To paint it use flat black water washup house paint, and then lightly sand that for an even flatter finish.
You can safely use wood glue or gorilla glue to glue foam parts.
Best rule of thumb: if its water based, its safe.. if its chemical based, it’ll eat the foam.
I think I posted some other useful foam working tipis in my build thread here.
I’ll second everything Gareee said.
I used wood putty and it worked great.
As far as rough edges go, sometimes you can sand them smooth. I had 3 different grit sandpapers that I used (and I forget the grit). One was for shaping the foam (it would take foam off without leaving holes), one would smooth that down, and the final grit gave everything a really smooth texture.
If you try really coarse sandpaper, it will just bite holes in the foam.