Bob Flexner's book "Understanding Wood Finishing"

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Forum topic by dvail12 posted 06-06-2018 12:34 PM 558 views 0 times favorited 4 replies Add to Favorites Watch
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22 posts in 2574 days

06-06-2018 12:34 PM

Is a pretty good reference for wood finishing. It doesn’t answer all of the questions I come up with, so I am asking this question of my fellow Lumberjocks.

I just made a screen door out of reclaimed long leaf southern yellow pine. Not easy to work with but very pretty grain and pretty hard and rot resistant. It will be exposed to morning sun. I would like to keep the natural grain and not paint. Many years ago I heard a story about tung oil. I was told that on old wooden work boats tung oil was used because no sanding or scraping was required to maintain, just apply a few more coats. Perhaps true, perhaps not.

In Flexner’s book, he says at least 5 coats for water resistance. So I put pure tung oil cut 50/50 with gum turpentine and wiped on a thin coat. After an hour or so, rewiped with a clean cloth. Let dry for 2 days, light 0000 steel wool and recoat with the same method. So far as predicted, finish is not consistent. Presumably because the porosity of the grain isn’t consistent.

Flexner states that many tung oil finishes are actually tung oil and varnish mixed and heated, or have no tung oil at all. So if some of these finishes are mixtures can a varnish/tung oil mixture top coat a tung oil sealing coat? And to answer my own question, top coating with varnish will mean a lot more maintenance due to sun exposure.

That was a long way to get to the final question. What would be the easiest way to keep a natural finish without having to sand, scrape, and recoat every two years?

-- Dvail12

4 replies so far

View chrisstef's profile


18021 posts in 3608 days

#1 posted 06-06-2018 12:59 PM

I dont think there’s much you can do aside from using marine varnishes. Even those will require maintenance.

“You gotta pay the cost to be the boss”.

-- Its not a crack, its a casting imperfection.

View dvail12's profile


22 posts in 2574 days

#2 posted 06-06-2018 01:16 PM

Regrettably, I think you are right. There is a two part varnish that I use on my boats. Lasts longer, but still requires the scutt work. I think the best practice with those finishes is to stay ahead of them.

-- Dvail12

View jimintx's profile


933 posts in 2186 days

#3 posted 06-06-2018 01:36 PM

dvail12, couple things:

I have used tung oil on many boats over many years. It was always on trim pieces, not the hull itself. It was used mostly on teak, and sometimes mahogany. I’m not sure a broad, boat analogy works for the situation you are working on.

However, for boats with wooden masts, the mast is not teak or mahogany, but mostly they are fir, or similar. Masts do sit out in the sun. To my knowledge, those get coated with marine spar varnish, and recoated from time to time as determined by visual observation of the degradation of the finish.

Given your door, I believe I would stain as desired, use a grain filler, then coat with several (3 to 5, maybe) coats of spar varnish. Then expect to sand and recoat, perhaps once a year or so, maybe longer…

If you can change the title of this thread to something about the actual question, I think you will get a better response rate. I read it because I recently acquired the book you mention, and was curious to see what you had to say about it.

In this thread, I think you really want to get some feedback on clear finishes for outdoor wooden pieces.

good luck.

-- Jim, Houston, TX

View Fred Hargis's profile

Fred Hargis

5921 posts in 3095 days

#4 posted 06-07-2018 11:32 AM

Well, I’ve suggested this before, and still think it’s a good approach. First, there’s not a clear finish that won’t some kind of maintenance over time….live with that or choose tinted paint. So, you wnat a clear finish that will last as long as possible between maintenance, and the true marine spar varnishes will do that. They are very expensive, take many coats for max protection, and are oil based which I’m not sure you want (I don’t know what “natural” is your opinion). So here’s another, cheaper, and easier approach. Try untinted exterior paint. If you want the look of oil finishes, go with an oil based version. You would want to buy the tint base for the deeper colors (usually #4, or labeled “deep color”, those for the lighter colors have some TiO2 in them. If you want a water clear finish, try an acrylic product, SW A100 will dry clear and have the outdoor protection you want. It may pay to be choosy when buying these if you choose to go this route, not all dry clear, and they pretty much all look cloudy in the can. But they work well, and may solve your problem. Again, this is the exterior deep color base, with no tint.

-- Our village hasn't lost it's idiot, he was elected to congress.

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