"Sealing edges of foam board for terrain" Topic

I was looking at using some foam board to construct some Halo structures to use with my skirmish rules, but never could figure out how to seal the edges. Without sealing the edges, it a) would look like crud, and b) I couldn't use spray primers or paints without melting the foam.

I had an inspiration, and tried it out, and it works. I used some Milliput, smearing it firmly into the foam, then using an razor blade to smooth it so that it was level with the cardstock covering the foam. As an unexpected bonus, it stiffened the foamboard a bit so it is stronger as well.

Picture of test piece:

Not sure if anyone had tried this in the past, but I'd never heard of the technique before. In any case, hope it helps someone.

Modge Podge or Gesso works, as well as brush on craft paint or latex paint. You can even use masking tape

Problem with tape is that it might eventually lose its grip.

Would acrylic paint melt the foam? I believe they sell spray paint specifically for foamboard.

Spackle would work, if the board wasn't flexing in use.

Might get shrinkage from the Milliput.

Kevin Smoot has covered things pretty well.

I suggest adding color to either the Mod Podge or Gesso, low cost craft acrylic paints work well for this. It helps to see the coverage and can aid in the flow of these. Depending on the effect you are going for, adding a very fine grit can also be helpful in hiding the fact it is foam under the paint. Also multiple coats are always better than one thick one.

I'm skeptical that I'm going to be able to use Modge Podge to seal the edges without a) getting it on the cardstock and smudging it up, and b) said Modge Podge not causing the cardstock to curl/change its shape. Nonetheless, since my wife does have some Modge Podge on hand, I'm going to try it on a scrap piece of foam board.

I'll report back on how it went. Certainly it would be cheaper to use Modge Podge instead of Milliput.

Acrylic paints do not melt the foam, as they are water-based. Solvent based, spray paints, dissolve the foam.

Most YouTube crafters use Mod-Podge (water-based, PVA Glue-based) to seal up foam. It lends a small amount of stiffness to the foam surface.

Once the foam surface is sealed with Mod-Podge, it can be painted with solvent-based paints, without issue, as long as all of the foam surface is protected by the Mod-Podge.

As it is water-based, it might affect the wood pulp within the paper, but so will water-based acrylic paint. Experimentation is king, billclo. Looking forward to hearing about your results. Cheers!

These are foam board. I sealed the edges with PVA then applied artists full body acrylic paint neat from the tube when I did the stucco on the walls (I always use tubed acrylic for this, a thin coat roughed up whilst wet. It isn't cheap but, it goes quite a long way. Unlike plaster/filler mixes it doesn't chip. Bricks are thin card applied before stucco; the stucco is put on thicker where the two meet to form a 'lip' and, on the top part of the 'bricked' walls where the stucco has 'fallen away', the paint is used to make the brickwork 'rounded'.

Multiple coats of elmers glue has worked for me. The blue foam requires less coats. It does make it brittle.