How to Fiberglass over Styrofoam?

Iron Forge

New Hunter
I am working on an Iron Man project as outlined in the Sarlacc Pit. It is being carved out of blue styrofoam, the type you buy at a home improvement store for insulation. The I am adding the nesessary details to it, I feel that in ourder to fiberglass a negative copy I first need to add bondo or some other smoothing agent which can then be sanded to perfection then waxed and the whole 9. I have some of the materials at home so I can test it out, but what are your thoughts. How would you proceed? I want to make a negative, and then a positive from fiberglass to make the actual helmet.

Has anyone used the blue or pink foam before? Thanks in advance for the help.

Muad Dib

Active Hunter
I don't know about the "blue" but with regular syrofoam, the best advice is to put aluminum foil over the foam and press it into all the detail as best you can. The resin will eat the regular foam.


Well-Known Hunter
I've used resin/fiberglass weave and matting on the pink insulation and it hasn't eaten it too much... but i think you would at least want to put a coat of something over it, bondo or otherwise.

just so we're understanding you...

you are making a positive of the armor piece/helmet in insulation.

then you want to resin/harden that so you can add further detailing with another material..

then from ALL of that you want to make a silicone mold jacket?

and once you have a mold pump out the pieces?

it should work...just make sure you coat the insulation/whatever you sculpt with something that won't inhibit the silicone from curing...or get eaten up by casting/molding materials.

wouldn't want all your work to be a waste

Iron Forge

New Hunter
I tested the Bondo out on a scratch piece of foam. There is a minor consuming of the foam by the process. I am currently in the process of bondo' ing it. It should be finishing soon.


Jr Hunter
Has anyone tried using Aqua Resin instead of fibreglass?

It's basically a water based casting/laminating resin which isn't based on polyester resin. It's water based and water soluble, so you'll probably find it won't eat into the foam.

It costs about 50% more than polyester resin, but sets just as hard and of course it's non-toxic and non-flammable so you can use it indoors the same as you would with plaster or emulsion paint (just wear old clothes). You can rinse your brushes out in water and use them again instead of throwing them away, if you spill some just wipe it up with a damp cloth.

I'm using it for an Iron Man helmet / armour project at the moment: Manhelmet/ Mancostume/

The finished pieces look and feel the same as fibreglass once they are set, and I've still used glass-fibre surface veil / mat to give the pieces strength


hey xrobot - nice work
so u used aqua resin and FG matt? great idea. was getting a litle worried abt using polyeser resin due to having 3 little ones and dodgy UK weather.

Nice to see a UK prop maker! can u pm supplier pls ;P



Jr Hunter
Great tutorial. Did you like the Aqua Resin? how easy was it to use and where do you purchase it?

Yes, I like it a lot. It's as easy to use as plaster of paris, but sets a LOT harder - pretty much the same as fibreglass (without actually testing it to destruction).

Check out for info and distributors - I got it direct from Aqua Resin...
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