Strange epoxy problem

I completely sanded my boat, but then decided to apply a thin coat of resin in a few places that I thought could use some extra protection. I wiped the hull with a damp rag to get rid of the sanded epoxy dust and let it dry for a couple of days. After applying the resin, it started to set up, but it didn't stick in certain areas. There are holes about 1/4 inch in diameter where there is no resin, surrounded by areas covered by resin. (Sorry, I don't have a digital camera to post a picture.) 

 Anybody know what's going on? I'm using MAS slow hardener, so I don't think it's blush, but I'm guessing there must be some sort of contamination on the hull. If you decide to apply resin to an area that's been sanded is there some sort of prep that needs to be done first?

Thank you,


10 replies:

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RE: Strange epoxy problem

Ah, the dreaded fish eye problem. Not really so strange or uncommon, Mark. There are a few causes, contamination from oil (possibly from your hands) or dust, surface tension, probably others. No big deal, just do a light sanding over those areas and roll on another thin coat of epoxy. Once it's all sanded nobody will ever know they were there.

George K

RE: Strange epoxy problem

Thanks, George. My hand prints are all over this project, so that's probably what caused the problem. I sanded off the mess and applied a new coat and it looks OK again.


RE: Strange epoxy problem

I had the same problem as Mark when filling the deck on my MC 16.5 Hybrid.  I had been following all the tips for preventing fisheye on the CLC builders tips.  I have used this garage  for several year as a woodshop and have never used aerosols or WD-40 ETC. 

My only guess was that it started when I used some syringes to measure as my pumps were getting old.  So following CLC advice I rinsed it in denatured alcohol, sanded as much as I dared, scuffed the fisheye spots with a scotch brite pad, and rinsed in alcohol again.  

It covered 90% of the fisheyes over the next two coats.  Then last night I applied what I hoped to be the last coat of epoxy and it beaded off the boat like it was covered in Rainex.  It was the worse coat yet as 80% of the epoxy didnt stick and the fisheyes were 2-3- times as big.  Some as big as a quarter. Last nights coat was with a new batch of epoxy and new pumps.  I am so frustrated and angry at this point that I barely slept last night.  

I would be extremely greatful for any ideas at this point as I have no clue what is causing the fisheyes.  Also I asume that if I just sand it and apply the varnish it too will fisheye?  




RE: Strange epoxy problem

It's possible that you have amine blush that is interfering with subsequent coats.  Although MAS isn't supposed to blush, it can happen.  I noted that you're working in a garage, and if it's hot, you're more likely to get blush (particularly if you had a good deal of time between coats).  I'm not sure what else would cause the problem to that degree all over the boat unless you had a bunch of contaminates in the air - but you indicated that isn't likely.  If it's blush, you can just rinse it off the boat with clean water (some people use soap) and allow to dry before adding a fresh layer.

I had some minor fisheye problems, which I think resulted from too thin a coat when the surface tension pulled the epoxy into pools. However, that doesn't sound like what's happening here.

All that said, I'm new to this as well, so others may have better ideas.  Best of luck solving the problem.


RE: Strange epoxy problem

That sounds like serious contamination. Besides the sources already mentioned, there's heater exhaust, dryer exhaust, motor exhaust, tack rags, dust rags that had been in a dryer with fabric softener and contaminated alcohol. Any chance that any of those got near your boat?



RE: Strange epoxy problem

Zach and Laszlo,

 Thanks for the reply.  I will try washing it with water.  I have been using the MAS with slow hardener, and my shop is air conditioned around 72 when I'm epoxying.  I have been vigilant about sprays in the shop for years.  It has a natural gas heater vented outside (it hasn't run for months)  no dryers and I cant fit a vehicle in the shop. The alcohol should have been clean I never reuse it,  I didn't use a tack rag but I did use paper shop towels.So I am going to try rags with no softener, and rinsing with lacquer thinner (per CLC advice this morning) and see what happens.  I thought I had it licked and then it came back with a vengeance.  Thanks



RE: Strange epoxy problem

I have heard that some denatured alcohols are recycled.  Check the fine print.  These shouldn't be used to clean anything you want to put a finish on.  Sandpaper bought in a store where someone used a silicon or oil spray could contaminate your hull.  Laszlo's list is a good one to check your building space against.  If you can't nail down the contaminate, use a virgin solvent and clean, unwashed rags (paper towels?) to wipe your hull just before you apply the next epoxy coat.  The solvent needs to be dry, not aged; waiting leaves time for contamination.  Good luck.

RE: Strange epoxy problem

Thanks, I did use new sandaper from Home Depot yesterday and the front of the package was open.  Hadn't thought of that.  I also didn't know that about the alcohol.  Laszlo's list is much better than the builder tips on CLC website, but I have been watching out for those things.  Hopefully with a wash, different sandpaper, new solvent and rags, followed by epoxy will do the trick. 

RE: Strange epoxy problem

At this point I would begin to suspect the epoxy itself is contaminated.  The problem you describe seems rather extreme considering the care you are taking.  The odds against contaminated sand paper, etc seem pretty high.  I would get a new set of resin and hardener, sand all the old off and try again. 

RE: Strange epoxy problem

Well the problem I had was with brand new epoxy and pumps, but I just finished about an hour ago and there are only a few maybe 7-8 small  fisheyes about 1/8" that I think will disappear with sanding.  So I am not sure where the problem was but it seems mostly resolved.  Thanks again for your advice.

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