Varnish vs. polyurethane - Kinda long story - SailNet Community
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post #1 of 5 Old 07-08-2007 Thread Starter
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Varnish vs. polyurethane - Kinda long story

So this weekend I put three coats of "varnish" on the exterior teak parts; 4 handrails, the companionway hatch and surrounds, and the rails that the cabin hatch slides in. The teak had never been varnished before, and was pretty gray and dirty. I gave everything a quick hand sanding, (220grit) and then ran a tack cloth over everything. So far so good…..

I then dug around in the storage closet and found an old can of combination stain/polyurethane varnish, (light maple), but rather then spend good money on the correct varnish, I used this crap. Not only did it turn the nice clean teak a really dark, dirty brown, but it looks like I intentionally painted it.

Fortunately, after one coat I ran out of the maple/stain/varnish stuff and headed off to West Marine to make another sketchy purchase. As I was reading labels, it occurred to me that I probably shouldn’t put real varnish (like Spars) over this other crap, as it might not adhere, or it might cause some weird chemical reaction; so I decided to get some MORE polyurethane varnish. This time I went with clear, hoping that a few coats of high gloss sheen might hide the brown stain. Well….needles to say, it didn’t hide much, but after two more coats it sure is shiny!

Anyway, as I was finishing up, these two guys stopped by to give me hard time about working instead of sailing, when one of them saw the polyurethane varnish and said “You can’t use that stuff on the exterior!” and I’m like, “What!?” I consulted the can, and it was pretty silent on the issue of interior vs. exterior, it only suggests that I not apply when it’s below freezing, (duh).

So my question is… I screwed? Is it all going to flake off after the first full moon? Or what? Would it help to apply another coat of real varnish on top?
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post #2 of 5 Old 07-08-2007
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A lot of the polyurethane varnishes aren't designed for outdoor use. I would strip it and go with a good exterior grade varnish.


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post #3 of 5 Old 07-08-2007
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I redid my front door with a polyurethane that said on the can it was for outside use. Read the can carefully as I also have a can that has the stain mixed in that says not foe exterior use. I believe the major difference is UV inhibitors are added for exterior use.
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post #4 of 5 Old 07-08-2007
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Did the same thing a few years ago. I had some Minwax Spar Urethane, rated for exterior use, and thought, "waste not, want not". After one year the cellophane effect took over. It seems to lift, almost from underneath, and seperates from the wood in small sheets like it was cellophane being peeled back. You have to remove it or, do as I did, tolerate it peeling for a year or so and then remove the rest. The UV inhibitors are not up to the task of the marine environment.

Fortunately, i got some good advise here on sailnet for removal. A heat gun works great at softening and removing it. You must be careful with it's use as it will soften the surrounding gel coat as well. You soften small sections at a time and then scrape them off with a putty knife or plastic scraper, being careful not to gouge the wood or gel-coat. If you inadvertently heat the gel-coat, be very careful not to gouge it with your scraper and allow it to cool-it'll be fine then.

After removing the 98% you can get with the heat gun, go over it will sandpaper to clean it up. Do not get agressive with the sandpaper, you'll just remove wood needlessly. Use the heat gun again if you encounter resistance. After that you can use some oxalic acid to clean up the teak. you can find it at the hardware in crystal form or it is the active ingredient in some deck cleaners. Cleans the teak up beautifully. Wet the gel-coat down with water before applying and wash down well afterwards. Let dry.

I used conventional spar varnish on mine. The West Marine Skipper's is rated well. Good old spar varnish is far superior to the urethane based "varnishes" at resisting UV light. You should plan on adding a top coat each season. Some carry an old nailpolish bottle with some varnish in it, a small piece of sandpaper, so they can repair any damage that may occur over the sailing season. Fixing those dings as they occur helps to keep the coating intact and does not allow moisture to get under the coating.

If you do a seasonal topcoat or two you can reduce your brightwork maintenance to a minimum. If you are too lax about it, you'll be back to stripping it down sooner than later.

Many like Cetol. Check out the old threads on it's use. If you want that deep wet look you have to finish the Cetol off with their gloss topcoat. There is some pigmentation, orangeish i believe, in the regular Cetol. Cetol Light is supposed to be less tinted. It's a little pricey, too.

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post #5 of 5 Old 07-09-2007 Thread Starter
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Thanks for the advice. I like the heat gun idea, (I bought one just recently to remove some hull stripes). I think I'm going to wait it out and see how long it lasts, then I'll attempt to remove it
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