Epoxy fisheyes over old plywood

[RJTangen]

Hi all,

First, I apologize if this has been covered elsewhere - I searched first, but couldn't find my particular issue.

Situation: I'm in Portland, OR, refinishing a 1966 Calkins Bartender - ply on frame construction. 19' trailer boat. I think the plywood is fir. The polyester based fiberglass on the the boat's bottom was cracked and delaminated in places, so I peeled it off, sanded the bare wood smooth with 80 grit, and am now attempting to apply a marine epoxy/fiberglass replacement bottom. The hull is plenty strong, so I'm really only looking for adhesion, abrasion resistance, and waterproofing from the epoxy.

The trouble I'm having is that the epoxy goes on fine, but about 15 minutes into the cure, it starts to crawl and fisheye, resulting in a very rough surface with ridges, valleys, craters, and rims. When it first happened, I sanded it all off down to the bare wood, then washed with acetone and papertowels - 4 total washes - and re-applied. It happened again. No change. Next, I took it back down to bare wood and scrubbed different areas with soap & water, TSP & water, acetone, and in one spot nothing at all - just sanded clean. Put on new epoxy, with the same result in each area. Everything I've read says that fisheye comes from surface contamination, but I've gone to great lengths to avoid that - new brushes, new mixing containers, new mixing sticks, no waxed containers, gloved hands only, etc.

I'm using TAP Plastics Marine Epoxy with slow hardener, which I'm told is a good product. I'm well within the temperature range of the epoxy, and it cures and hardens nicely - just not flat! I called TAP and they were at a loss - but they also said their epoxy expert had gone home for the day, and I should call back tomorrow. I'll do that. I've not tried any other brand of epoxy, and I'm a little leary of spending the money for what amounts to trial and error.

Here's a link to a couple pics of the boat and a close-up to a patch of lumpy epoxy: https://picasaweb.google.com/rjtange...eat=directlink

(sorry, I tried to attach it here, but it says the file size is too big?)

I've exhausted my very small bag of tricks and am hoping someone here has experienced and conquered a problem like this! As a side note, I'm utterly amazed at how this stuff sticks to absolutely everything except what I want it to! It's on my glasses, my watch, my fingers, the steering wheel of my truck and my garage floor. No fisheye in any of those places!

Thanks!
Randy

[Oldad]

No idea, you've already done all of the things I would have tried. Definitely looks like it is reacting with something in or on the plywood unless you have a bad batch of epoxy.

Oldad scratching his head over this one... wait, what acetone did you use, some acetone leaves a residue... could that be it??

[RJTangen]

I used Klean-Strip Acetone, from a new can. Bought it at Ace Hardware up the street. http://www.wmbarr.com/product.aspx?catid=21&prodid=39

I have not tried cleaning the wood with Denatured Alcohol yet, and I've seen some people have had success with it. I'll try that next.

I also suspect it may be the epoxy. West System claims to have anti-fisheye properties, so I may buy a small quantity of that and try it.

[David G]

My first thought is the epoxy. I've never used Tap brand, and never known anyone who has. If you decide to use another brand, there are some proven choices available locally. System3 at Crosscut Hardwood. West System at West Marine.

You can try the acetone wash. You could also try applying additional layers of epoxy (after sanding a bit) until the fish-eye stops (which it may or may not). Definitely talk to the resident Tap expert. I'd be more incline, however, to contact the tech line at West System... and trust their advice. Keep us posted.

[JimConlin]

Lose the acetone.

Wash with water and a scotchbrite pad.
Dry with paper towels.
Sand flat.
Recoat.

[David G]

Jim,

Sounds like you think it's simply a case of amine contamination. From the description... it sound more radical than that...

[skaraborgcraft]

Im just wondering what someone may have put on the ply before applying the original polyester and cloth,especially if it "peeled off" clean without taking any ply fibres with it. I wouldnt bother with acetone,but if you can get some automotive silicon remover from a body spray shop,that would be worth a try. I cant see any reason why the epoxy itself would react like that,so some kind of reaction is going on with something left in the ply.

[bahma]

I suggest you try puttying your epoxy on a test panel of new plywood, and then a couple of coats of Smiths CPES before your resin.

Must say I've never heard of Tap resin.

Norman.
Man o War Cay

[bahma]

What I meant was, do the test panel, if result OK, then apply CPES to the boat, or to be sure do a test panel with CPES then the TAP.

Norman

[RJTangen]

Thanks all for your speedy replies!

Testing the epoxy on new plywood is a great idea! I'll do that for sure. If it crawls on new plywood I should have a great claim to get my money back from TAP, and a very good reason to shift to a different brand! (TAP Plastics is a retailer/wholesaler of fiberglass and plastic materials in the Pac NW region - all the way to the SF Bay Area, I think. Neat store, nice guys, and local.) I have also considered the CPES route, and believe that to be a very valid option - even without considering the current fisheye problem.

It sure does seem like there's something in or on that plywood. I did a little sandpaper work and found that after sanding the epoxy off, it still causes plain water to fisheye! That's on what appears to be clean, dry, freshly-sanded-with-80-grit plywood. A great deal more sanding eventually produced a surface that the water didn't react to, so I guess maybe I've found my solution, as unpleasant as it is. 1. Sand off grumpy lumpy epoxy. 2. Sand off oily/contaminated wood 3. Test bare wood with clean water looking for fisheye/surface tension action (bad) or smooth sheeting & penetration (good). 4. Dry, dry, dry, then wait for it to dry some more. 5. Pretend it was all a bad dream and start over.

While I can't imagine that the original builder would have put anything on the plywood prior to the old glass, I wonder if the old polyester resin deposited some kind of chemical byproduct similar or analogous to amine blush into the wood, which may have contributed to the delamination issues to begin with. I'm really grasping at straws here, but it seems conceivable. I guess another very long shot would be the fact that the inside of the plywood was originally (and is now) finished with a linseed oil derivative (Daly's Seafin Teak Oil). It doesn't make sense to me that oil would soak completely through 3/8" marine ply, though. Maybe around fasteners or loose joints, but not the entire surface. No way.

Thanks again, and I'll be sure to close this loop if I find a solution. It must be a rare problem indeed, as even good 'ol Google doesn't offer up much help. Some surfboard and fly rod builders have had fishy epoxy too, but no definitive solutions could be found.

[Tom Lathrop]

Fish eyes "cratering" is a problem that vexed us early on with epoxy. System 3 was particularly susceptable and no easy solution was found until the epoxy suppliers did somethng to solve it. Now, its rare. If the resin has high surface tension, it will tend to pull away fro the slightest contaminant or irregularity on the surface. Low surface tension material like that of soap, fish slime or other wetting agents tends not to crater at all. In spite of their claims otherwise, it usually the epoxy that is at fault.

Of course wax, oil or even fingerprints can cause craters too.

[David G]

It's entirely possible that there is some 'product' on the plywood of your hull that's causing your issues. There were a lot of home-built Bartenders built over the years. A good number of 'innovative' handy men who might have thought it a fine idea to 'preserve' the plywood with any number of concoctions. OTOH - if yours was factory built, by Caulkins, you can probably assume it didn't come with some contaminant. Though said guck could have been added later.

[PaulT]

I do think it would be prudent to stop using solvents to try to clean this up. Likely the solvents are simply diluting the contaminant and driving it deeper into the ply with each application. Soap and water, perhaps, but acetone, alcohol, various thinners...most are petroleum based and may be leaving oily residues. Also, a small leak in the original skin and the same oily residue you find on the outside of a hull is now trapped between the polyester fiberglass and the plywood. May have been part of the problem.
I really don't know the solution, but the CPES would be next on my list, as well as the previously mentioned test panels, were it mine.

[wizbang 13]

wax in the polyester? is the 80 grit gumming up ? I duuno, that is a mess.I would grind the living daylights out of it with 36. I have never washed up with acetone.
And I would use dynel,for the things you want, not fg.

[Oldad]

There is a residue from inexpensive hardware store acetone. If you can get some,the kind that is sold to auto body repair shops, you should have better results. It has no residue. I did a quick google search and found numerous references to the residue left behind by hardware store acetone. Of course it could be something altogether different.

Oldad hoping you get it figgered out

Just read Wizz's post and recall the polyester wax thing.. that might be it

[SchoonerRat]

You might also look for environmental contamination. Are you coating outdoors? What is your neighborhood like? Nearby industry that might be releasing something oily or waxy into the atmosphere? Are you near an airport or power station? Anybody nearby spraying silicone lube (death to any finish)?

If you're doing everything right and you're confident that the problem isn't your epoxy (I have no experience or knowledge of TAP) you might need to look further than your workshop.

[Cuyahoga Chuck]

A lot of commonly available solvents are products of re-distillation of scrap solvents. They usually can't get a really pure product. Body shop solvents have to be pure to avoid befouling a surface so that the paint won't cure properly.

[Todd Bradshaw]

Contamination is everywhere - even from exhaust if your "boat shop" also happens to garage your wife's car in its off hours. I suppose it could be the surfacing wax from the polyester if the builder used waxed resin for the initial layers instead of laminating resin, though that stuff usually migrates away to the surface, not down toward the wood. In any case, the fewer solvents you put on things that you want to epoxy coat, the better off you will be. All that washing with various chemicals is just asking for trouble.

[RJTangen]

So today was a science day. Here's what I did:

I had a piece of scrap fir plywood that I bought new about a month ago. It's never been finished, but it's not been babied either. It's been in the bed of my truck, on an old greasy work bench, on the garage floor, handled with my grubby mitts over and over, and exposed to the atmosphere in my "boat shop" for the same amount of time as the boat hull. I didn't wear gloves. I used a previously used mixing cup and stir stick and a new foam brush. It was cool, cloudy and humid out, and my attitude was skeptical and slightly surly. I made no effort to hold my mouth right.

I epoxied four 4" wide strips on the scrap wood. The first strip was with no treatment at all. Second strip had been sanded with 80 grit, using sandpaper that I used on the boat hull yesterday. Third strip was sanded and then scrubbed with acetone. Fourth strip was sanded, scrubbed with acetone, and given a prolonged, close-up blast from my compressed air hose (I had used compressed air at one point to blow dust off the hull - thought there may be compressor oil mist in the air).

Results: NONE OF THEM FISHEYED. Not even a little bit. They all layed nice and smooth, penetrated into the wood what appears to be an appropriate amount, and are happily curing just like the epoxy gods want them to. The smoothest, prettiest strip is the one that was sanded only. The others have very slight imperfections.

My conclusions:
1. The epoxy is fine. It may or may not be as good at dealing with contaminated surfaces as some other brands, but given a fair shake, it works right.
2. Sandpaper residue didn't cause it.
3. Acetone didn't cause it. This is self-evident, as the original fisheye happened before I had applied any acetone. I understand now that acetone likely didn't help anything, and probably made it worse.
4. Compresser oil didn't cause it. Again, I now know it's not good practice, and will cease its use.
5. Old boats can be frustrating.
6. Mechanics (like me) should stick with iron and steel and not carelessly dabble in the voodoo magic that is wood finishing.

To further nail this thing shut, I went back to the boat hull - right next to the spot where I took the photo of the fisheye - and sanded it heavily. I used what remained of the epoxy from the sample strips and the same equipment, and in the spot where I sanded, it did not fisheye at all. It DID fisheye around the edges where the sanding feathered out, but in the middle, it was (and is) nice, smooth, and well-behaved.

I have no idea what's in that wood, but I know I don't want it there, and I know I can get rid of it by sanding. It seems like the hard part is going to be knowing when I've sanded enough. There is no visible color or layer. I guess I just need to sand until I think I'm done, then do it all again. Fisheyed epoxy is nasty, expensive, and frustrating, and I don't ever want to see it again.

Thanks all for your attention and input. If anyone would like some quality time behind a sander, let me know!

Randy

[SamSam]

So today was a science day. Here's what I did:

...my attitude was skeptical and slightly surly. I made no effort to hold my mouth right.

There's the secret, show no fear.

Forget the 80 grit, use 36 as Wizbang says. Rent a sander or visit the pawn shop if you don't have one big enough. A 6 or 8" random orbit air powered would be the most excellent solution. Pawn shops are full of tools nowadays, offer them about 1/3 of what they ask. Again, show no fear. The best way to clean the surface is to brush with one hand and strong vacuum with the other, instead of blowing dust off, it sucks the stuff out of the nooks and crannies and pores better.