Blue foam, primer, epoxy and mush

[itoolfred]

I must have done something very wrong. After going to the shopbot camp here in phx, I thought I'd try a little blue foam carving for a project for my son's birthday. Purchased the blue foam from HD, carved, primed with Kilz II, then epoxy. The epoxy went thru the Kilz and began to eat at the foam before hardening. I also tried to prime with a pva primer and had the same reaction. Any ideas what I'm doing wrong. I'm pretty sure I'm getting a good coat of primer over the entire surface... My question is what primer/coating are you using to seal the foam before epoxy. I know Bill P gave some information on this but don't have anything from my notes.
Thx,
Fred

[Brady Watson]

Fred,
Epoxy will NOT eat the foam. You are not referring to polyester resin as epoxy by chance are you? ANY solvent based paint will eat the foam!

To get the finish that you want, you will want to get yourself some FSC-88-WB (http://www.precisionboard.com/Mar/product_data_sheets/companion/fsc88.htm) The WB means it is water based. After that dries, sand and coat with epoxy if you need to.

Check out the ears (http://www.flickr.com/photos/campshopbot/sets/72057594119444771/) They were made from 3" blue DOW insulation foam, coated in FSC-88-WB, sanded and painted with latex.

-Brady

[billp]

Fred,
Brady is right. The FSC -88-WB is what I always use, and had recommended at the Phoenix Camp. Kilz has also worked for me in the past so I too would be suspect of the "epoxy(?)" you are using. What brand is it?
If you rub the FSC 88 into the foam and let it dry, you can then sand it smooth and brush epoxy over that surface. The primer should work as a barrier coat and protect the foam.
Is there ANY chance that your Kilz was the culprit in melting the foam? I think that Kilz 2 might be water base, but Kilz could be solvent based...

[itoolfred]

Brady and Bill-
Yes and Yes. Was using an oil based kilz and a polyester resin. Switched to water based kilz and epoxy and it looks/works great. I've never worked with foam before and it sure cuts faster than the mdf & birch I cut all day. Thank you both for the advice and setting me straight.
Fred

[artisan]

Fred, another excellent coating/sealer for foam is Zinsser water based Shellac. It actually will create a "vapor barrier" and won't allow anything to pass. It dries VERY quickly and sands nicely without the risk of solvents as it is water based.

Be advised that while FSC 88 works well enough...it IS still a solvent based product (mineral spirits) and can ruin more delicate and sophisticated projects. It should never be used on open cell foams like EPS (styrofoam). Another great and safe sealer is Minwax Polycrylic, which forms a plastic (acrylic) finish over your piece.

Epoxies are excellent chemically inert finishes that won't harm your foam through solvents....but can cause damage through heat if applied in heavy coats or allowed to puddle. Happy carving.....D

[Brady Watson]

Darrell,
As posted above:

"FSC-88-WB...The WB means it is water based"

Standard FSC88 is solvent-based. The WB version is not. I've found it is best to coat the part with FSC88WB and THEN use epoxy. This will eliminate the 'pimple' effect on raw foam that you get with the pink and blue stuff. Not sure how the white fairs with straight epoxy.

-B

[artisan]

Sorry Brady...I stand corrected. I've only seen the solvent based product and look forward to trying it out....D

[nschlee]

Fred, Try System Three's WR-155 Primer, this is a 2 part water based epoxy primer. It is easily mixed, can be sprayed, rolled or brushed, we use it for many different applications. It sets up rock hard and is waterproof, most any top coat can be used over it, as long as the primer is COMPLETELY cured. It's available in white or gray, it is not cheap, $88 a gal., but it is a fantastic product. We use it mostly for signs and boat hulls.

[itoolfred]

Neal,
Where do you purchase the WR-155? Just looked on their website and they don't have anyone here in AZ.
Thx
Fred

[nschlee]

Fred,
We're a System Three dealer, but the frt. from Alaska would be a killer. System Three sells direct (retail), the WR-155 is not considered hazardous, it can be shipped UPS Ground or mailed no problem. It is also available in quarts (approx. $40).

Another excellent Sys III product is their WR-LPU Clear Gloss 2 Part Polyurethane Top Coat, also water based. It is water white, has UV absorbers, will not yellow or loose it's gloss for years (depending on exposure) & is moisture, solvent and fuel resistant, $48 a quart with the cross-linker.
If you login to their website they have pricing, info sheets and MSDS available.