uncured epoxy problem

[Bluegill]

What should I do ???? I applied 6 oz fiberglass and epoxy to the bottom of my new build Bluegill skiff. I made up 5 batches of 12 oz of epoxy, because that is the biggest measuring container I had. I either did a poor job of stiring/mixing or measuring hardener and resin. Anyway, one batch did not cure. I partially removed uncured epoxy using a squiggee, rags and alcohol, and rags and acetone. Squiggee, rags and alcohol, and rags and acetone only partially removes epoxy from the fiberglass. What should I do ???? I thought I should just let it set-cure-dry for a day, then apply additional coats of epoxy to fill-in fiber weave.

[chas]

Heat first, to get the mix to set; sounds like it may be too late for that. More heat and a steel scraper to remove the uncured section. Pumps are a Godsend for mixing epoxy. / Jim

[JimConlin]

Errors in mixing epoxy are less likely if you adopt routines and make them habitual.
Dunno how I adopted it, but my ingrained habit is to stir a pot of epoxy 64 strokes (that's 4 x 4 x 4), scrape the sides and do 16 more.

[John How]

I started mixing by weight. Small digital scales are cheap and very useful and your mix will be spot on every time.

[P.I. Stazzer-Newt]

I started mixing by weight. Small digital scales are cheap and very useful and your mix will be spot on every time.

YUP. I switched after an unfortunate experience with those damnable pump things.

Kitchen scales inside a clear polythene bag.

[Sayla]

What should I do ???? I applied 6 oz fiberglass and epoxy to the bottom of my new build Bluegill skiff. I made up 5 batches of 12 oz of epoxy, because that is the biggest measuring container I had. I either did a poor job of stiring/mixing or measuring hardener and resin. Anyway, one batch did not cure. I partially removed uncured epoxy using a squiggee, rags and alcohol, and rags and acetone. Squiggee, rags and alcohol, and rags and acetone only partially removes epoxy from the fiberglass. What should I do ???? I thought I should just let it set-cure-dry for a day, then apply additional coats of epoxy to fill-in fiber weave.

Hard to visualise where your problem is - the one batch that didn't cure, where is it - everywhere? one section? whole topcoat? - something seems to have gone wrong with the mix and will likely have to come off - I suppose it would seem that you could wait, as it would be coming off anyway if it doesn't set

The upside is that you're far more unlikely to poorly mix a batch ever again - it happened to me, once.

sayla

[TerryLL]

I'm also a strong advocate of mixing by weight. Using the weight method allows precise measurement of amounts down in the 1/4 ounce range (7 grams).

But doing a 12 ounce batch (340 grams) that doesn't go off indicates that one or more essential steps in the measuring and mixing process was missed. The key to consistent results is to have an established routine, as Jim mentions. I developed a checklist that I lay right next to the scale with boxes to check off as I mix up a batch, insuring that I don't miss a step. A bit anal, yes, but over the course of 4 epoxy-ply builds I have yet to have a batch that didn't set properly.

[Eddiebou]

If you can find a mixing vessel with straight sides, like cylinder, coffee can, etc., not flaired or tapered, you can simply make incremental marks on a stick. It doesn't matter what increment, 1/2", 1", whatever you like. If the epoxy is 5 to 1, make 6 marks, 5 for the resin, 1 for the hardener. This makes it pretty easy to mix whatever size batch you want.
Remember that epoxy will go off quicker in a deep, narrow vessel than it will in a shallow, wide one. After mixing in the cylinder, pour it into a shallow pan. If you need to set it aside and do something, put the pan in the refrigerator.
It is really easy to mess up counting pump strokes ,etc. Stir it untill you think it's stired enough, then stir it more, and more, but get it out of that deep container within a few minutes. I've had epoxy get so hot that it melts a plastic container. It will burn your hands, fume and crystalize on a hot day, especially after adding filler.

[Bluegill]

Hard to visualise where your problem is - the one batch that didn't cure, where is it - everywhere? one section? whole topcoat? - something seems to have gone wrong with the mix and will likely have to come off - I suppose it would seem that you could wait, as it would be coming off anyway if it doesn't set sayla

This epoxy was applied as the initial coat for fiberglassing the wood hull bottom.
Around 25% of the fiberglass area on the hull bottom has the non-setting-up epoxy.
I have gone over fiberglass several times with alcohol, acetone, rags.
The fiberglass is stretched tight on all sides of non-set-up area, that is, there is a big oblong area with non-set-up epoxy and fiberglass, surrounded by set-up epoxy and fiberglass.
The un-cured epoxy is underneath the fiberglass. I have removed MUCH un-cured epoxy, but the fiberglass surely inhibits complete removal.

[JimD]

...
The un-cured epoxy is underneath the fiberglass. I have removed MUCH un-cured epoxy, but the fiberglass surely inhibits complete removal.

Take off the glass. Throw it away. Start over. Since the uncured epoxy has already had plenty of time to soak into the wood you may have a tough time cleaning it. Lots of acetone is what I'd try. Bummer.

[TerryLL]

It's time to think about cutting out the FG over the uncured section and cleaning that area properly, then laying in a FG patch over the area with new epoxy.

edited to add: Follow JimD's advice.

[Bluegill]

Take off the glass. Throw it away. Start over. Since the uncured epoxy has already had plenty of time to soak into the wood you may have a tough time cleaning it. Lots of acetone is what I'd try. Bummer.

How about applying hardener to uncured epoxy ????

[wizbang 13]

negatory.
treating epoxy like polyester is what got you into this jam

[Bluegill]

I think this happened.
When mixing, I had 4 containers before me; 2 resin and 2 hardener containers. I think I poured 8 oz of RESIN, the added 4 oz of RESIN (instead of hardener).

[JimD]

How about applying hardener to uncured epoxy ????

Nope, won't work as you can neither be certain you're adding exactly the right amount and even if you could you can't mix it. Unfortunately, there isn't anything to be done other than get rid of it all, clean it up meticulously, and start over.

[Gib Etheridge]

At this point I would cut out the uncured area then use a scraper to clean it down to wood.. Next I would use a heat lamp to heat a small portion of that area. Then mix a small batch and use it to apply a small piece of glass leaving a tab of glass sticking up then immediately remove the heat. Once the new resin is cured I would grasp the tab and rip it off. If wood comes with it you can go from there.

[Bluegill]

At this point I would cut out the uncured area then use a scraper to clean it down to wood.. Next I would use a heat lamp to heat a small portion of that area. Then mix a small batch and use it to apply a small piece of glass leaving a tab of glass sticking up then immediately remove the heat. Once the new resin is cured I would grasp the tab and rip it off. If wood comes with it you can go from there.

Many days before fiberglassing, I applied 2 thinned coats of epoxy to the plywood bottom, so the new epoxy will not penetrate into the wood as you suggest. I removed the uncured epoxy and fiberglass. A razor was used to cut fiberglass, then the epoxy and cloth peals off very, very easily. A heat gun was used to remove epoxy where it is was glued down tight. I removed fiberglass in a rectalinear shape, which will make it easier to cover the repair job. I was surprised how removal was so easy.

[PhaseLockedLoop]

I'm also a strong advocate of mixing by weight. Using the weight method allows precise measurement of amounts down in the 1/4 ounce range (7 grams).

But doing a 12 ounce batch (340 grams) that doesn't go off indicates that one or more essential steps in the measuring and mixing process was missed. The key to consistent results is to have an established routine, as Jim mentions. I developed a checklist that I lay right next to the scale with boxes to check off as I mix up a batch, insuring that I don't miss a step. A bit anal, yes, but over the course of 4 epoxy-ply builds I have yet to have a batch that didn't set properly.

Keep in mind that ratios by weight are usually different that ratios by volume: 3 to 1 by volume won't be 3 to 1 by weight unless the resin and hardener weigh the same per volume, which they hardly ever do. Fortunately mix ratios aren't so fussy that the stuff won't cure anyway, but it's best to try to get it right when you can.

[RodB]

Many days before fiberglassing, I applied 2 thinned coats of epoxy to the plywood bottom, so the new epoxy will not penetrate into the wood as you suggest. I removed the uncured epoxy and fiberglass. A razor was used to cut fiberglass, then the epoxy and cloth peals off very, very easily. A heat gun was used to remove epoxy where it is was glued down tight. I removed fiberglass in a rectalinear shape, which will make it easier to cover the repair job. I was surprised how removal was so easy.

Then you are home free... just clean all well with acetone and then sand the underlying cured epoxy with 80 grit... and even the surrounding glass that was saturated with properly mixed epoxy and then begin with the new cloth to remedy the surface.

Good luck... we all make mistakes now and then.

RodB