Getting fed up with MAS epoxy

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Re: Getting fed up with MAS epoxy

Postby DanaDCole on Sun Sep 13, 2015 12:50 pm

Well I guess I'll try it although I don't see how it is possible to have amine blush or any surface contamination. As I said I'm using MAS with slow hardener and scrubbing it down good with denatured alcohol before I start. Also, I had the same problem, though not quite as bad, with the first coat, which was over bare wood that had also been cleaned with alcohol.

I'll sand her down pretty smooth and not worry about sanding through to wood here and there. I happen to have some Interlux YMA601V Fiberglass Surface Prep which I purchased by mistake but they won't allow me to return. It is for removing all contaminants and amine blush. So maybe it's a good thing I have it. Or I could use MEK, but it seems to me the YMA601V might be exactly the right thing.
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Re: Getting fed up with MAS epoxy

Postby craig on Sun Sep 13, 2015 5:36 pm

I bet you had tape there to block off paint from the sides. Residue from the tape will do that to epoxy (at least the punters tape that I'm using does).
Titania, launched January 2015
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Re: Getting fed up with MAS epoxy

Postby DanaDCole on Sun Sep 13, 2015 5:47 pm

Hah! Such smart people on this forum. That's why I rely on it. :) One thing, though--what the picture shows is the second coat that I applied over the first before "thin film set," so I don't know how paint residue would get through the first coat. Anyway, I'll sand it down, wash the crap out of it with MEK, and try again.

If that doesn't work to heck with it. I know someone who has a beautiful boat except that the side panels show patterns under the paint similar to what I get after the initial sanding of the MAS epoxy. Obviously he gave up too.
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Re: Getting fed up with MAS epoxy--Final Decision

Postby DanaDCole on Mon Sep 14, 2015 11:05 am

This morning I tried a small experiment. Instead of sanding all the affected areas I tried sanding a small section of the port toe rail. Though trying to sand off the lumps while keeping the pressure light, I still sanded through near an edge. So I changed to 120 grit and sanded that entire section down to wood, except for a few small areas that retained some epoxy, followed by thorough cleaning with alcohol. Here is the result:
Image

Then I applied a thin layer of epoxy. I tried to get a shot of that immediately afterwards, but it turned out to be too far out of focus. Anyway, I can say that at that time the surface was fairly smooth, with a few brush strokes here and there.

Here is a closeup of the forward end of the re-epoxied area after one hour:
Image
This is one of the sections that was down to bare wood, so given that fact and the thorough cleaning I can't see how there could be any contaminants remaining (maybe the mahogany still contains some liquids). Though this is an improvement, I can guarantee that any attempts to sand it smooth will definitely take it down to bare wood in spots.
So my decision is to go ahead and sand all the bright-finish areas down smooth (except on the inner side of the toe rails where water can collect) and varnish them. If I have to re-varnish every year or two then so be it.
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Re: Getting fed up with MAS epoxy

Postby jwv630 on Tue Sep 15, 2015 10:45 am

Hi Dana:

Nasty....Suggest you consider emailing John Harris, the owner of CLC, directly on this problem. Include your pictures with the email. He has always been very gracious and responsive to my many questions.

Good luck,
Jimmy V
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Re: Getting fed up with MAS epoxy

Postby craig on Tue Sep 15, 2015 12:59 pm

I am extremely shocked that this still happened to freshly-sanded wood. I still think it's a surface "contamination" issue caused by an oily substance. You must be right, and it's just the inherent oily nature of the wood? I'm not sure.

I think it's totally acceptable to say FORGETIT and move on. I am still curious whether a thorough scrub with dish soap would fix the problem.
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Re: Getting fed up with MAS epoxy

Postby John C. Harris on Thu Sep 17, 2015 9:25 am

DanaDCole wrote:I got a shot of some of the epoxy on the toe rail. In order to show the texture, the only light is coming from outside the garage so I had to use a very slow shutter speed (1 1/2 sec) to keep enough of it in focus, even at f11. Image
The epoxy is applied over several previous coats that had been sanded smooth. In this case the only places it had sanded through were at a few of the corners. What I may do is sand this smooth and only recoat areas that sanded through, leaving them a little rough.

I didn't get any pictures of what the epoxy looked like before it started to "curdle" but I can assure you that it went on very smoothly, just a few brush lines.




I'm absolutely certain that I'm seeing surface contamination here. This isn't some innate problem with MAS epoxy. ALL of the epoxy brands are fussy about contaminated surfaces. SOMETHING is on that surface that's causing the epoxy to bead up, a phenomenon known as "fisheyes." I would scrub surfaces with denatured alcohol and a clean rag before applying epoxy. Believe me, if MAS did that all the time, I'd drop it like a bad habit!

In terms of the leveling properties of epoxy, it's true that none of the brands are going to smooth out like varnish. It's just not in the nature of epoxy to do that, though there are things you can do to help. Very thin coats, for example, but I'm always in a hurry to build thickness with my epoxy coating so I don't have the patience for that. A lot of professionals use a heat gun after rolling out a coating to lower the viscosity so that the epoxy levels better, but this doesn't work in every application.

Epoxy: A miracle material, but with its own frustrating idiosyncrasies. I teach an entire one-week course on wood-epoxy techniques at the WoodenBoat School every summer, and we're still only able to scratch the surface of all the tricks out there.
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Re: Getting fed up with MAS epoxy

Postby DanaDCole on Fri Sep 25, 2015 9:23 pm

Thanks John. This was very odd indeed. These particular bits of wood were the only places I had this problem, and you can be sure that I had cleaned them and scrubbed them well with denatured alcohol before applying epoxy. The thing is, I had the same problem with subsequent coats of epoxy! Later I epoxied the bits for the dropboards, which were cut from the same mahogany board and they came out just fine. The only thing I can think to attribute it to is atmospheric conditions, although as far as I could tell they were very similar in both instances. That leaves solar flares as the only possibility. :D Well I'm not going to worry about it. If I have to re-varnish those small bits every year or two, so be it.
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