What's the best external finish for wood?

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What's the best external finish for wood?

Postby martin54 » Fri Apr 26, 2019 6:22 pm

Need some expert advice on finishing external wooden signs if possible.

I would like to give the sign the best possible chance of lasting & as finishing is something I am very weak at thought it best to ask for help. this is a piece of Oak, the Fairy inlay is Hornbeam. It will be fitted to the top of a post in Woodand so exterior but not in direct sun light.
I have used Automotive Lacquer on a number of projects with good results but these have all been internal so not sure if that would be OK or if I would be better with something like Yacht varnish. I already have both of these, or is there something else that would be better?
I have already checked & I can use either the Laquer or Varnish with the Paints I have used to colour the text.

wishing well oak.jpg
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Re: What's the best external finish for wood?

Postby Leo » Fri Apr 26, 2019 6:28 pm

I don't have any experience with exterior finishing of wooden signs, but I have spend a lot of time in and around the marine environment in my younger days. I have done marine varnish on boats.

I GOOD marine spar varnish is thick and flexible. It needs to be flexible to it can expand and contract with sun and cold in a very corrosive and hostile environment - on a boat in salt water.

Spar varnish IS a yellowing varnish.

My recommendation is to at least consider it. Epiphanes is a well known good brand
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Re: What's the best external finish for wood?

Postby ger21 » Fri Apr 26, 2019 7:14 pm

Seal with 3 coats of epoxy, followed by several coats of varnish, or an automotive urethane clear coat.
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Re: What's the best external finish for wood?

Postby garylmast » Fri Apr 26, 2019 7:45 pm

A while back I carved an Eagle, using cedar and maple to put on top of a gazebo I built in my backyard. The cedar was from 25-year old fence I tore down, so I though that would be the perfect wood for the body. After staining, I also coated it with a clear, UV lacquer top coat. After the second year, being in the full sun, I started getting some rot, so I coated it with a clear Marine Grade Epoxy that was UV Resistant, that I got off of Amazon. I also wasn't shy on how thick I put it on. That was last year. I just took this picture and it looks as good as I coated it yesterday.

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Re: What's the best external finish for wood?

Postby wb9tpg » Fri Apr 26, 2019 8:10 pm

ger21 wrote:Seal with 3 coats of epoxy, followed by several coats of varnish, or an automotive urethane clear coat.


Epoxy then Shellac (for UV protection) - requires yearly coating

or

Epoxy, then Spar Varnish - longer lasting



For the Epoxy it's always West System Epoxy with 207 clear hardener = $$$$$ but it's the best.
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Re: What's the best external finish for wood?

Postby TReischl » Fri Apr 26, 2019 9:26 pm

Nice eagle Gary!

All we can do is try to keep Mother Nature from running wild with our stuff.

I once asked my uncle what was the best finish. In his inimitable way he said:

"Look at it this way, if there was a finish that stood up to time and lasted forever, farmers would have been using it long ago because no one likes painting a barn."

There is some wisdom buried in there.
"If you see a good fight, get in it." Dr. Vernon Jones
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Re: What's the best external finish for wood?

Postby Phil » Sat Apr 27, 2019 1:29 pm

In my experience the best route is to select a species that has natural rot resistance. A google search came up with these:
Redwood.
American mahogany.
Cypress.
Western red cedar.
Pacific yew.
Teak.
Black walnut.
White oak.


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Re: What's the best external finish for wood?

Postby martin54 » Sat Apr 27, 2019 3:39 pm

Thanks for the replies people, bit of a surprise to see coat with Epoxy & then Varnish, I was expecting something along the lines of one or the other lol I know there is nothing that will prevent Mother Nature so was just looking for something to help persaude her to slow down a little :lol: :lol:

Phil, in the UK most of those would be difficult to get hold of or I would have to buy as PAR timber but a search which includes UK at the end puts European Oak towards the top of the list & that's what I have used. Interestingly Larch is only listed as moderately resistant & I thought that was right at the top of the tree (pun intended).
I did originally start this with a piece of Larch for that very reason but had problems with paint bleed, maybe because of the grain structure I'm not sure but I thought I had sealed it properly before painting :oops:
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Re: What's the best external finish for wood?

Postby Savannahdan » Sat Apr 27, 2019 8:50 pm

One of my latest projects is a set of slab oak legs for a concrete top garden bench. Frankly it might have been quicker, simpler and longer lasting to have just constructed a mold for replacement concrete legs. But, I had this chunk of oak slab and thought it would be nice to route designs in the legs, including the curved leg design, inset a corian v-carved emblem and use lag bolts to provide levelling for the legs. I got a recommendation from a forester to use tung oil to protect the wood. So, I coated, soaked and brushed on so much tung oil that I lost count but sort of stopped when they seemed to be loaded. I also decided to use some spray on automotive lacquer to make it a little shiny and maybe fill in open grain. The legs sit far enough under the top that I don't think they'll get much rain and sun. I'll try to get some pics to share. I'm sure that the legs will need some re-coating somewhere down the pike. The forester who made the recommendation uses the tung oil on slab benches he makes for clients that have them sitting outside. He says they only have to re-coat as needed and don't have to scrape off pealing varnishes, etc.
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Re: What's the best external finish for wood?

Postby wb9tpg » Sun Apr 28, 2019 1:01 pm

martin54 wrote:Thanks for the replies people, bit of a surprise to see coat with Epoxy & then Varnish,

Epoxy has little UV protection and needs a Spar Varnish or Shellac coating to protect it
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Re: What's the best external finish for wood?

Postby ger21 » Sun Apr 28, 2019 1:53 pm

While shellac itself is UV resistant, it is not UV blocking, so it offers zero UV protection for the Epoxy below it.

If the finished piece will be in the sun, the finish won't last. There's no way around.

If you want it to remain looking "like new", wood species is irrelevant.

Some of the woods mentioned above are much more weather and rot resistant than others, but they''ll need to become gray and weathered long before that becomes an issue.
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Re: What's the best external finish for wood?

Postby Phil » Sun Apr 28, 2019 3:27 pm

http://www.hardwooddistributors.org/pos ... fied-wood/
Martin, I've never used this but it looks like a good choice for outdoor projects. Restits rot and insects.

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