What to use to harden foam.

[the rice shield]

Hello I'm new here and have recently been making a halo 3 battle rifle out of extruded polystyrene. Right now it is pretty close to finish but I want something to put on the outside of it to make it more durable. I heard using bondo will ruin the foam or something. So what else could I use? I heard using regular old elmers glue and brushing it over the top would be fine. Would that actually work?

 

[XxDrxNinjaxX]

Hey I'm basically a noob as well when it comes to foam. I'm using EVA foam mats on my build and I have used bondo on it with no problems if I don't try to manipulate it out of shape. If I deform it at all the bondo cracks. I am using plastidip spray and it is working so far. It is that rubber coating that you see on pliers and stuff. I think if you put a base coat of plastidip then you will be able to use whatever hardener, be it bondo or plastics, without any troubles.

 

[Icon Props]

I was thinking of trying a rondo mixture. I haven't tested it yet, maybe someone else has tried this & will pass on there results.
Jim

 

[dung0beetle]

You can fiberglass it, cover it in casting resin, plastidip, etc. Before you do any of these, coat it in pva (white or wood) glue to seal it. The resins will not melt the foam if it is sealed in pva glue.

 

[Cinderblock]

eva foam doesn't melt from resin, so it doesn't need to be sealed generally (styro-foam does though) Although if you wish to harden it make sure it is a fairly sturdy job, because the flexibility of foam will tend to cause the resin to crack. Someone found that if you seal the foam in PVA then coat it with plastic resins like smooth cast it is very effective though.

 

[the rice shield]

thanks for the replies. Can someone link me to some pva so I have an idea what Im looking for

 

[the rice shield]

Oh wait nevermind I know what pva is now. So I can just use regular old elmers school glue?

 

[dung0beetle]

eva foam doesn't melt from resin, so it doesn't need to be sealed generally (styro-foam does though) Although if you wish to harden it make sure it is a fairly sturdy job, because the flexibility of foam will tend to cause the resin to crack. Someone found that if you seal the foam in PVA then coat it with plastic resins like smooth cast it is very effective though.

It doesn't get eaten by the resin, but the resin/hardener generates heat which can deform the foam, pva glue acts as an insulator to reduce/diffuse the heat so it doesn't affect the foam so much. If you are using thick stuff, it has little effect, but thinner stuff like craft foam will deform more. I think Ithica posted a video testing foam vs resin. Whatever you use, it's a good idea to test it out on some scrap to see if you are about to ruin a lot of hard work.

 

[the rice shield]

so I decided to go with pva glue and was wondering, should I water it down a little bit before applying it or not?