Outdoor clearcoat/varnish?

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Forum topic by Don Butler posted 06-11-2010 02:58 PM 13081 views 2 times favorited 8 replies Add to Favorites Watch
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Don Butler

1092 posts in 3393 days

06-11-2010 02:58 PM

Topic tags/keywords: question walnut finishing

I realize that marine spar may be the best, but what other finishes are there to use in outdoor projects?

I have a job building a truck bed for a custom street rod. He wants it to be in Black Walnut and it should resemble a fine furniture finish.
It will be driven on the street, and likely will be rained upon. It also may be put to the test with various things carried in the truck, like coolers, folding chairs, etc.

So what is your best advice.
I have no experience with projects like this.


-- No trees were damaged in posting this message, but thousands of electrons were seriously inconvenienced.

8 replies so far

View CaptainSkully's profile


1598 posts in 3556 days

#1 posted 06-11-2010 04:58 PM

I work at West Marine, and most woodworkers use West Systems epoxy with the 207 clear hardener to encapsulate the wood truck beds, then they coat it with Epiphanes (properly thinned) or some other varnish for UV protection. I’ve heard good things about West Marine’s Five Star Premium Varnish, but haven’t used it yet.

-- You can't control the wind, but you can trim your sails

View a1Jim's profile


117091 posts in 3575 days

#2 posted 06-11-2010 05:04 PM

Sounds like good stuff

-- wood crafting & woodworking classes

View swirt's profile


2736 posts in 2969 days

#3 posted 06-11-2010 05:10 PM

Sikkens Cetol-1 works pretty good. Though it imparts quite a bit of tint due to the UV inhibitors. It does build a nice finish though. Three coats to start, then 1 topcoat as the finish wears off. The wear-off rate depends on exposure and abbrasion. I have cedar adirondack chairs that are exposed to sun, rain, and snow and sit outside 365 days a year. I top coat them roughly every 3 years. I have a table that is under cover in a gazebo that is 10 years old and I have never had to put another top-coat on.

It is a breathable finish that won’t crack like poly. The only time it may crack is if the wood develops a check that it can’t span.

-- Galootish log blog,

View hObOmOnk's profile


1381 posts in 4125 days

#4 posted 06-11-2010 08:49 PM

I too am a fan of Sikkens Cetol.

Avoid the low-end so-called Spar Urethane consumer-grade finishes. They are insipid.

Here’s a good source for nautical finishes, including spar varnish: Jamestown Distributors.

-- 温故知新

View Jim's profile


7 posts in 2904 days

#5 posted 06-11-2010 10:41 PM

Oh no…......this is my first post….....but I have to disagree about using Cetol on black walnut. I agree with CaptainSkully…........West System epoxy is the easiest to use resin system, and will give you superb results.
(I built a sea kayak with it… first real wood project. Simple to use, yielding superb results.) Once you completely seal the wood, varnish it with a marine grade varnish for UV protection.

As swirt posted, Cetol “imparts quite a bit of tint”, due to pigment in Cetol. I tried Cetol on a few outdoor objects, and was not impressed with how it looked a year later. With beautiful black walnut, I would suggest not covering it with a pigmented product. Opinions are like noses, Ford/Chevy, etcetera…........if you live near eastern Virginia, I’ll give you some Cetol to test for yourself. At the minimum, do a “trail run” using Cetol on a piece of black walnut, to see if you like how it looks, then ask your customer if he likes how it looks.

hobomonk and swirt, please pardon the difference in opinion, I’m not wanting to sound belligerent.

-- Just easing along; life is good.

View gerrym526's profile


274 posts in 3806 days

#6 posted 06-11-2010 11:18 PM

As mentioned with Cetol having a UV inhibiting tint-there’s a very good reason for this. UV breaks down the cellulose structure of the wood. The more UV protection (e.g. tints, translucent, or solid body stains), the longer the wood lasts. That’s why no clearcoat finish will keep wood outdoors from deteriorating, and latex house paint on your home’s trim will keep wood from breaking down forever (it completely blocks out UV).
You’ll need to advise your client that the more outdoor usage the truck bed gets, the shorter the life of the “fine furniture finish”-that way he won’t be unpleasantly surprised and mad at you.

-- Gerry

View swirt's profile


2736 posts in 2969 days

#7 posted 06-12-2010 03:51 AM

No worries Jim. I have no problem whatsoever with differing opinions or even contradictions. I agree, it would be a shame to cover black walnut with any tint.

I guess part of it all depends on the use and how much outside exposure it will actually get. My complaint with any of the epoxy or spar systems is that if left outside, they will fail eventually, and when they do, you pretty much have to remove it all and start over. There is no renewing it with just another coat.

If the custom street rod only spends a handful of days a year outside, then there is no issue and anything with some uv inhibitors will work.

-- Galootish log blog,

View swirt's profile


2736 posts in 2969 days

#8 posted 06-12-2010 04:12 AM

FineWoodworking did a torture test of a bunch of finishes, (did not include any sikkens products) but it is an interesting read.
also here is some followup discussion from one of the editors

Don, one other thought I had was to recommend Ipe as an alternative to Black Walnut. Similar look, but Ipe is quite a bit more weather resistant on its own.

-- Galootish log blog,

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