Repair for Bad Epoxy Mix

[sailalex]

After putting on a final coat of epoxy on cedar planks for a Handy Billy (sand and fill complete)I made the dumb mistake of changing the measure routine and ended up with half the hardener needed and it is uncured.
I am asking for your experience on several repair options:
1) lightly brush only hardener over the uncured epoxy with the hope it will "kick"
2) try another coat of properly measured epoxy over the existing uncured coat with the hope it will chemically bond and harden the entire surface
3) of course the worst option(from a labor standpoint) is to take a heat gun and remove all uncured and use acetone for the residual
I appreciate any of your experiences with this problem; thanks for your assist.

[JimD]

Bummer. Been there, too. There is one and only one fix. Remove the bad batch completely.

[Steve Miller]

Agree with Jim on that. Sorry.

[Nicholas Carey]

Sadly, epoxy isn't polyester. Adding more hardener won't "make it kick", as the hardener in epoxy isn't a catalyst in the same way that the catalyst (MEK?) used in polyester work is.

Epoxy hardener has to be mixed well with the resin in the right proportions in order for the chemical reaction to take place. If you have insufficient hardener, you'll wind up with uncured resin; if you have too much hardener, you'll wind up with uncured hardener. In either case, a sticky, gooey mess.

And adding a properly mixed batch on top of the uncured mess won't help: it might cure, but its adhesion will only be as strong as its substrate (and in the case of uncured epoxy, that ain't much).

Sorry…as noted above, heat gun, scrapers, vinegar, rags and labor is your only solution.

Wear protective gloves and or a barrier coat: exposure to uncured epoxy will [eventually] sensitize you to it.

[Keith Wilson]

Normally, I'd say there's no alternative to scraping it all off, but here there may be hope. It's a non-structural coating with too much resin, and will be painted over later. People who know a lot more about epoxy chemistry have told me that a resin-rich mixture will eventually self-polymerize and cure. OTOH, only half the hardener is pretty extreme.

How is it now? Rubbery? Sticky? Liquid? If you're talking about a heat gun to remove the residue, I suspect rubbery. Can you wait a week and see what happens? If it appears to be hardening, you might put on another layer of epoxy (correct mixture, not excess hardener), assuming the bad layer will continue to cure underneath. It might work. One way or another don't paint on hardener, that will just make it worse.

OTOH, calling the manufacturer might be a good idea. Fortunately, the only batch of epoxy I've really botched involved a carefully measured mix of two parts resin and one part resin, :rolleyes: so it wasn't too bad to wipe off. If you do have to remove it, you might look into a less-toxic alternative to acetone. One of those d-limonene based orange cleaners might work; they cut uncured epoxy pretty well.

[sailalex]

Thanks for all your responses. The surface is more "sticky" than anything; it leaves a fingerprint and has been on for about 3 days. It seems ( my hope?) that today seems a little firmer than in the past two days so I am going to let it stay for about a week and see what happens.
My friend also suggested applying a new coat following the logic that since one coat is so thin, it would be okay. Has anyone tried to put a coat on top or heard of someone doing that? The idea is that "some" of the hardener from the topcoat would be enough to help "kick" the underlying coat enough to finish the cure.
I intend to check with West tomorrow but they likely will say take it off as they do in their book.I am also running a test on another piece of wood duplicating the condition and checking the results.
Thanks again and if anyone has experience or heard of someone putting another coat on top of uncured epoxy, I would really like to hear of the result.
Will keep you posted. Thanks!

[Tonyr]

Adding a new coat on top of an earlier uncured/semi-cured coat (half the hardener, i.e. a 10:1 mixture, Vs the 5:1 called for) results in a cured coat on top of the uncured coat. Sorry! I have just tried this, and am now in the sticky process of removing everything. I cut through the cloth, and then peeled it very slowly off in strips about 10 inches wide. The remaining goo is a scrape-able layer - I have done about a quarter so far. I will finish with solvent (vinegar would be nice, if it works).

Fortunately, the affected area is only about 6 square feet, out of some 180 sq feet total, since I am epoxy-ing the cloth in batch mode, rather than all of it at one time.

Welcome to the miss-mixing club.

Tony.

[paul oman]

Get off as much of the sticky mess as possible (scrape, solvent etc) then topcoat with a correctly mixed batch.

Mistakes like this happen all the time!

regards

paul oman
progressive epoxy polymers
www.epoxyproducts.com/marine.html (http://www.epoxyproducts.com/marine.html)