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Removing a bad batch of epoxy

Posted: Sun Nov 06, 2022 5:11 pm
by jbo_c
So, I can finally stop being proud of myself for not having mis-mixed a batch of epoxy. I finally screwed one up Friday evening.

One disadvantage of working wet on wet: if you screw up the first batch, you have to remove all subsequent work to get to it and fix it. BAH !!!! Happily, it was a (relatively) small overall area and I’ve pulled off the three(!!!) layers of fiberglass above the bad batch.

The question is, how do you remove the gummy bad batch now that it’s exposed? It was a “neat” coat prior to glassing, so there’s no more glass to get off. You can’t really sand it - gums up the paper instantly. I thought maybe vinegar would do it since you can clean uncured epoxy with it, but that doesn’t seem to be working.

I did do a root cause analysis and I think I have a method to make sure it doesn’t happen again.

Thanks.

Jbo


PS: After the realization and subsequent correction, I may be looking for a new church. I you know one in the Gainesville, Georgia area that might still accept me, reach out. LOL

Re: Removing a bad batch of epoxy

Posted: Sun Nov 06, 2022 9:09 pm
by OneWayTraffic
I'd start with acetone, after you've scraped everything you can.

Re: Removing a bad batch of epoxy

Posted: Mon Nov 07, 2022 11:03 am
by TomW1
+1

Re: Removing a bad batch of epoxy

Posted: Mon Nov 07, 2022 11:30 am
by bklake
I have not used this tool for this situation but have for other epoxy related situations. A carbide blade paint scraper. I can't explain why but it does such a great job removing stuff. Far better than a similarly sharp steel scraper.

Re: Removing a bad batch of epoxy

Posted: Mon Nov 07, 2022 2:13 pm
by jbo_c
I use one for removing threads and roughness in finished glass layups prior to sanding. I wondered how that would work.

Jbo

Re: Removing a bad batch of epoxy

Posted: Mon Nov 07, 2022 6:03 pm
by jbo_c
Tried the acetone when I got home this evening. Definitely not quick if it’s going to be the best. Did a fair amount of scrubbing with acetone and a green pad. Still tacky. Will work on it some more.

Jbo

Re: Removing a bad batch of epoxy

Posted: Tue Nov 08, 2022 3:29 pm
by TomW1
jbo_c wrote: Mon Nov 07, 2022 2:13 pm I use one for removing threads and roughness in finished glass layups prior to sanding. I wondered how that would work.

Jbo

Sanding that not cured epoxy will gum up a sandining pad in about a minute. 8O Tom

Re: Removing a bad batch of epoxy

Posted: Tue Nov 08, 2022 4:09 pm
by jbo_c
Undeniable, Tom. I was referring to the scraper. :)

Have also wondered about using a wire wheel but don’t want to be flinging uncured epoxy all over myself. Can’t be healthy.

Jbo

Re: Removing a bad batch of epoxy

Posted: Tue Nov 08, 2022 5:08 pm
by OrangeQuest
Try going back to the vinegar and scrubbing pads. Maybe even try a little dawn dishwashing soap mixed in with the vinegar. If it is gummy, you want it to stop sticking to itself.

Re: Removing a bad batch of epoxy

Posted: Tue Nov 08, 2022 8:00 pm
by Jaysen
I'd use the scraper to get "most" of it off. Use the vinegar/acetone/soap, but with the scraper, you can just wipe the tool clean. You may want to take just a bit of the wood off with the scraper as well to get any bad gel out of the wood pores.

I found that "a scraper like device" (in my case random piece of sheet metal) made cleaning raw resin off a plywood floor much easier.

Don't ask. I'm not telling you how that happened.

Re: Removing a bad batch of epoxy

Posted: Wed Nov 09, 2022 10:50 am
by OrangeQuest
If you are still in the scrapping stage of removal, then use a vinegar/dawn soap mix to help keep the gunk from sticking to the scrapper and it will be more effective.

The hardest part is going to get out the epoxy that soaked down into the wood so any new epoxy will stick and bond.

Re: Removing a bad batch of epoxy

Posted: Thu Nov 10, 2022 9:37 am
by pee wee
Once the epoxy has been removed from the surface I'd scrub the area with acetone or MEK. What a pain!

Re: Removing a bad batch of epoxy

Posted: Thu Nov 10, 2022 12:56 pm
by Fuzz
I bet you will not let it happen again! So a little good will come from this :wink:

Re: Removing a bad batch of epoxy

Posted: Fri Nov 11, 2022 3:00 am
by OneWayTraffic
OrangeQuest wrote: Wed Nov 09, 2022 10:50 am If you are still in the scrapping stage of removal, then use a vinegar/dawn soap mix to help keep the gunk from sticking to the scrapper and it will be more effective.

The hardest part is going to get out the epoxy that soaked down into the wood so any new epoxy will stick and bond.
If that's a concern, and especially on a small but critical area, I'd get out the grinder and a 36 grit. Remove the top layer of plywood and build up with some extra glass. Larger areas acetone, and then give it a week or so before trying again.

Re: Removing a bad batch of epoxy

Posted: Mon Nov 21, 2022 9:23 am
by jbo_c
Basically, didn’t have much luck with any of the chemicals. Ended up using a grinder with a wire wheel, then wiping down with laquer thinner and following with 50 grit paper.

Also seemed to help that it was really cold. The bad epoxy firmed up a lot when it was cold, so made it a point of doing it early on a morning when it was right at freezing.

It did gouge into the wood and a few small places that had been glasses previously, but in general didn’t cause as much collateral damage as I thought it might.

Jbo

Re: Removing a bad batch of epoxy

Posted: Mon Nov 21, 2022 9:25 am
by jbo_c
Say ‘hello’ to my little friend.

Image

Re: Removing a bad batch of epoxy

Posted: Mon Nov 21, 2022 9:33 am
by OrangeQuest
I just had to remove a piece I glued in and realized it was in the wrong place, had to remove a 3' piece, I caught it just at the soft but not yielding stage of curing. Took my multitool with a straight 1.5" wide blade and started cutting it off. The epoxy just wanted to gum up and cutting was very slow. So I dipped a small sponge brush into vinegar and painted where I was cutting. The blade started cutting like butter without gumming up and was a lot easier to remove. All the remaining glue, I just used the blade and vinegar and scraped down to the neat epoxy that was below. You can't tell I screwed up at all. The blade was old and dull, the vinegar acted as a lube to keep the gunk from sticking to it. Maybe something to consider in the future if the need arises again.

Re: Removing a bad batch of epoxy

Posted: Mon Nov 21, 2022 9:58 am
by jbo_c
Good one, Orange. Hopefully I never need that information. :)

Jbo

Re: Removing a bad batch of epoxy

Posted: Sun Dec 18, 2022 7:01 pm
by TomW1
jbo did you get your epoxy repaired. Tom

Re: Removing a bad batch of epoxy

Posted: Sun Dec 18, 2022 8:34 pm
by jbo_c
I got all the goop off, but cold got here before I could go back over with good stuff. Looks like it will be spring before I I can finish the repair.

Thanks for checking in.

Jbo