What causes epoxy to do this?

I laid down this this, pre-tape coat in a warm garage (75-degrees plus), on warm structure that had been sanded to bare wood and wiped lightly with acetone, and then the acetone allowed to completely evaporate.

The goo seems to be repelled from areas Will the wetting coat do the same? It's a little alarming...

Thanks,

Curtis

(Sorry for the crappy phone pics).

 

Looking at it, It would appear to be contamination from silicone wax, though some oily woods do have a similar effect. Probably some minor cracks or pinholes and when you polished the boat the silicone based polish soaked the wood, or maybe the acetone cloth was used for polishing.

 

You seem to have some sort of surface contamination. The acetone wipe isn't a good idea. What looks to have happened is you've wiped it down and this caused a reaction, with tannins or oils in the wood, which though the acetone flashed off, the now diluted and partly liquified tannins reacted with the wet goo.

Also you don't appear to have sealed the wood, which tends to lock down these types of troubles. The first coat of epoxy over raw wood is the one that will have the most potential for issues, so extra care needs to be made to prevent pooling of goo on the surface, which prevents out gassing, plus make sure the work is clean and dry.

It's likely this is a combination of issues, another to consider is, the warm garage, but relatively cold wood. This is a guarantee for out gassing. The warm air will draw gasses from within the wood's cellular structure to the surface, forming bubbles in any pooled goo, many of which will pop.

Use the "mash and go" method I describe on my site for applying goo to raw wood. This insures you will not have out gassing problems. Also make sure the wood is just as warm, if not slightly warmer than the ambient temperature in the shop. The goo should (or could) be warmer than ambient temperatures. After sealing raw wood, there should be a dull sheen all over, no shine and possibly some seemingly bare spots. What this means is you've applied enough epoxy to soak in, but not so much that it pools on the surface. Once the sealing coat is dry, you lightly sand it and then you can "bulk" up subsequent coats of goo.

 

The boat was previously covered in glass with poly resin. It had all been stripped off (most of it - resin and all - just pulled off in a sheet. Nothing was applied to the wood except sandpaper after that. It is an old boat, with what appears to be ACX fir ply used on the skin.

Not looking forward to sanding it down to prevent the divots from telegraphing through, especially if epoxy reacts this way on the entire boat. What a massive P.I.T.A.

Thanks, Paul, I will go and read about the mash & go technique. Elsewhere (all over, really) one reads about pre-coating wood but never how much, how thick, etc.. I guess it's better to learn this lesson with a small strip along the edge than a quart all over the deck...

 

The initial coat of epoxy should seal the surface and prevent further contamination issues other then blush. If this surface is is preped and the sealing coated applied properly, it goes much nicer. It's probable you released some still trapped styrene based solvents, left over from the polyester sheathing. I know this sounds crazy, but amazingly enough, some of the cells in the wood, could still after all this time, have trapped pockets of chemicals that out gassed when the sheath was removed and the surface sanded (exposing the cell tops). When you get it sanded good, give it a a wet acetone wash down, scrubbing as you go, then wait a few days, before putting any epoxy over it. This should let you scrub out the other contaminates and flash off sufficiently, for a new coat of goo.

 

Paul, thanks for mulling this over and getting back to me. It actually makes a lot of sense.

There is, of course, a ton of information online about finishing new building material, but I have considered many times over the last several months, what effect - if any - the boat being as old as it is, might have on the refinishing - the old glues and filler material, paints (I've been careful about lead) and even the old resin formulation, and what kinds of problems they might cause.

I sanded, filled and faired any protuberances or depressions/scratches to within a couple thou, but pretty much ignored the tiny scratches or nicks that would easily be filled with resin on the first coat. As you can see in one of the pics there are voids where there are some very small nicks in the wood and that is common to spots that appeared as voids in the coat of goo. I figure that either some of the acetone easily penetrated and soaked in those areas that didn't dry in time, or, as you suggest, allowing a path for reaction and outgassing, or both.

At any rate, after your timely first response I went in and scraped the excess goo down to the thin first coat, and that seems to have done the trick as it is a continuous hard coat now. A good lesson learned. I will try as you have suggested, and this time let the acetone evaporate for a couple days followed with a mash & go coat. I don't anticipate any further problems.

Well, until I flip the boat to find out just how rotton the keelson is

As always, thanks to you and everyone who have responded

Curtis

 

The mash and go technique is only necessary on raw wood, where out gassing might be an issue. Subsequent coats should be as uniform as you can make them.

 

My experience has been that wiping with solvents frequently introduces contaminants.

My procedure is wash any existing epoxy coats with water to remove blush, sand with 80 grit, brush off the dust, than lay down the epoxy coat. Don't touch the sanded surface with bare hands because the oil on your fingers is a contaminate.

Try it and you will see that fisheyes are much less of a problem. If you do see a fisheye forming, you can get rid of it by quickly wiping the epoxy over that area off with a clean paper towel, the brush more epoxy over the spot you wiped.

Acetone should not be used anywhere near epoxy anyway, the correct solvent is denatured alcohol.

 

Thanks, guys!

 

Day 3 of wiping with hot water and Scotch Brite and I still have blush. The water doesn't lift it or dissolve it - it just smears around. The Scotch Brite picks some up, of course, but when I think I've gotten it all and let it sit over night to dry the area is still sticky. This is just a 4" strip around the sheer, I can't imagine going through this on a large area...

I'm two more days of frustration away from grinding it all down to wood, selling the epoxy on Craigslist and fiberglassing this thing. I've followed all the suggestions & directions to a tee and nothing is working.

I'm a survivor and incredibly stubborn person, but this just about has me beat...

 

Blush is water soluble, though a little soap helps. I use a few drops of dish washing liquid in a bucket and this is enough. What brand of epoxy are you using?

 

Fiberglassite.com. Wrote them and they replied that if the structure was below 65* that might prevent the epoxy from curing (NOW they tell me. I don't think the numbers on the web site are that low and I wouldn't have made the purchase if I had been aware).

I'm starting to question as to whether it is *all* simply blush.

After scrubbing the water in the bucket is cloudy, but the waxy substance on the scotch brite pad does not breakdown in hot water.

Doesn't look like the boat will be splashed until possibly the end of summer as I refuse to run a kero heater unattended. Believe me, house fires are less than fun.

This is a HUGE disappointment after almost 9-months work on all the structure.

 

The hardener must be pretty slow, because most will eventually cure at 65 degrees. Slow hardeners will have difficulty below this temperature. Damn, Fiberglassite products aren't cheap. Why them?

To answer your question, I think you might be right and the goo isn't cured yet. How easy is it to push a fingernail into the surface? Can you make a dent with it?

 

Yeah, got a nice reply from fiberglassite and I am pretty convinced it is uncured goo I am dealing with. Interestingly enough, it is far stickier on the side near the garage wall than it is on the more open side, so I think I need to move the air more efficiently in the space. I just need to adapt and configure the garage for extended warmer temps. It's drywalled and (I assume) insulated, so I will tape the window, get a small fan for convection and go get a 2K watt heater and just take it from there. I'm not beat yet!

I got 1.3 gal of epoxy for $85, and that was the best price I could find at the time. If I had known about the temp range needed I probably would have spent the extra for fast/cold weather cure at Paul O's place. Lesson learned, and that's the point, right? The learning, not necessarily the doing.

Thanks again for your support and advice, Paul.

 

Have you considered heat lamps? You can move them around and eventually get all the resin to fully cure.