Has Anyone Used Fiberglass Resin on EVA Foam?

indiefilmgeek

As I'm working on my son's Halloween costume, I have tried a few different build materials. I started with normal card-stock pep w fiberglass and bondo to harden and smooth the pieces. Recently, I created my son's Ironman neck seal out of 3mm EVA foam. This worked very well, and I decided to build the arms in the same material. However, I want the final arm units to be hardened.

So, I planned to fiberglass the 3mm foam, smooth any minor roughness with glazing putty and then sand them smooth before priming and painting them.

Last night I took two early 'test' pieces out and apply a liberal coat of fiberglass resin to the outside of the pieces. This morning BOTH pieces were still VERY tacky (if not out right wet). Resin that had dripped on the working surface had completely hardened, so I know the wetness isn't due to my mixing the resin wrong.

This afternoon I re-tested it and it's still tacky (although maybe slightly less so). Also... neither piece is very 'hard'. The whole piece still 'flexes' a lot. This has me wondering if there is a specific issue with the resin in combination with the closed-cell foam.

I'll include two pics just for kicks and giggles (since you can't tell anything from these really)...






So, has anyone had any experience (good or bad) with Fiberglass resin applied to EVA closed-cell foam pieces?

Thanks!

Termin8Anakin

Yeah I tried it just recently on EVA foam and it sucks. I tried it on thin and thick pieces too.
One reason is because the foam is flexible, but the MAIN reason is because it's just not being absorbed by the foam. A thick layer of resin goes absolutely rock hard (like the leftovers in your mixing container for example), but a thin layer might as well be nothing.

Also, the reason why the resin on the table is hard is because the table itself is a hard surface. The resin itself is still not strong at all.

One cheaper alternative (although it's also very time consuming), is to paper mache every surface, and then coat the dried paper with resin.
The paper will absorb it and harden just fine. I've seen quite a few cosplayers use this method with success.

Although if you're willing to spend the money you might as well just go with fiberglass matting or cloth.

mdb

I think what the OP was describing was the resin not curing. There may be something in the EVA that inhibits the cure.

I have used epoxy resin over foam and it cures fine. It also works over polystyrene without dissolving it so there is that going for the stuff as well

The foam though did not absorb much of the resin. I suspect had I tried I could have squeezed the foam and worked the resin in a bit more- fine if I was draping the foam over a form but not for a shaped foam.

indiefilmgeek

What type (or brand) of Epoxy resin did you use. I won't mind testing that out.

I tried to heat the fiberglass by using a blow-dryer last night when it STILL wasn't cured. Also, even where it was cured the piece was still SO flexible that I might as well have hit the thing with Plasti-Dip instead.

I'm a bit depressed. If I can't get something like the Epoxy resin to work, then I'm probably heading back to pep the thing in card-stock and head back to standard fiberglassing and bondo method.

TheNickFox

Have you tried hitting it with a heat gun (on low) or painting more hardener on top of the tacky resin?

And if that doesn't work, why not try urethane casting resin instead? You can paint it on, the fumes are safe, and when you use it with standard paper-based pep you can just slush it around inside the piece to harden it...no need for fiberglass.

You might want to try it on the EVA. Grab a trial size of smooth-on 320 or 321 and see what happens.

It's worth a shot since chemistry doesn't seem to be on your side with the EVA and polyester resin combo.

-Nick

Vermithrax 4

Another costumer asked me about this same subject and I did a test a couple days ago brushing fiberglass resin onto a 1/8" thick piece of foamy and I was quite pleased with the way it cured. It was a thin layer so it's still a bit flexible but created a very smooth, paintable surface. The brand of resin I used was Bondo brand purchased at our local NAPA. One thing you might try to enhance the curing is using a bit more of the hardening liquid than is recommended, that's what I did and it cured quickly and without the slightest bit of tackiness.

paladin

something i thought of, since pepkura is just card stock why no put a layer of water activate packaging tape on you foam the fiber glass it that way the paper is the medium thats coated and you still have the foam under it

indiefilmgeek

Yeah, I hit it heat - not much difference...

Nick, that's a good idea... I bought some generic epoxy to test, but I'll test this out as well before throwing in the towel!

I've found that the 'foamy' sheets from craft stores are different that the EVA foam I'm using. I haven't tried fiberglassing a foamy yet, but that might be an option if there is no other working solution for the foam I'm currently building with (and like a lot).

Great minds thing alike. I was actually just talking with someone about printing off the pepakura pages onto 'sticker paper'. Office stores sell full page sticker paper and all you'd need to do is paste it on the foam, cut, glue and then fiberglass/epoxy. I don't know if that justifies foam building over standard paper/resin/bondo building (some folks would say "why waste the time converting the pieces to foam-style construction when you could just fiberglass the darn paper pep and smooth it with bondo").

But if you hate sanding as much as I do... it might be worth it.

Thanks for all the ideas, thoughts, encouragement and prayers. It really helps to have a community like this - you all are awesome!

indiefilmgeek

To save duplication, I'm tracking all of my material tests over on the WIP thread for this project: STARTING HERE

P.S. mdb mentioned basic hardware store epoxy as a good hardening agent... Here is a little test footage of my epoxy over EVA foam. YOUTUBE VIDEO

I'm definitely using this for some of my pieces that need to be hardened!

Tigerblood

you'll probably have a better success using some laminating epoxy. EpoxAmite as a Smooth-On brand. But if you want to be more cost effective, go back to using Pep and 3/4 oz. fiberglass mat.