Spar Finish Flaking @ 18 months.

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Forum topic by Eric posted 12-30-2013 12:54 AM 2577 views 1 time favorited 25 replies Add to Favorites Watch
View Eric's profile


221 posts in 2538 days

12-30-2013 12:54 AM

I built this chair a year and a half ago.

It now looks like this:

Here’s a close-up of the arm:

Is this typical? Why is my finish peeling?

-- Eric

25 replies so far

View Loren's profile


10476 posts in 3675 days

#1 posted 12-30-2013 01:10 AM

Well, 18 months is a disappointing run for outdoor spar
varnish, but not unheard of. It’s the light that makes
it do that more than the moisture I think. Paint is
obviously easier to maintain. If you want to do the
varnish again, I suggest getting some chair covers
for when you aren’t using them.

View distrbd's profile


2252 posts in 2473 days

#2 posted 12-30-2013 01:21 AM

Isn’t spar varnish designed for boats to protect the surface from moisture and UV rays?I’m no expert but it looks like the moisture content in that wood was too high and the spar did not allow it to breath .

-- Ken from Ontario, Canada

View kajunkraft's profile


152 posts in 2237 days

#3 posted 12-30-2013 01:30 AM

Not that I claim to be an expert in this area, but I’ve always heard that UV from the sun needs to be reflected (deflected?). For this to happen there has to be some pigment in the finish (ie: not just a clear finish). Thompson’s Water Seal, for example, is something that always comes to mind for outdoor projects and they now promote a UV “inhibitor” for their finish. I build mainly outdoor furniture and use Ready Seal pretty much exclusively, although I’m sure others are pretty good too. I have never experienced the cracking/peeling that your pictures show. Nevertheless, there seems to be a lot of interest in a “shiny” finish, which I have not yet figured out how to achieve for outdoor furniture.

View Lee Barker's profile

Lee Barker

2170 posts in 2877 days

#4 posted 12-30-2013 01:59 AM

Ken, my understanding is that spar varnish is more flexible than regular varnishes so the exterior wood can expand and contract without affecting the finish.

Also, wood does not breathe. It takes in moisture and releases it as humidity and temperature vary.

This case is severe. I suspect, in addition to the UV damage, that the wood may have been moisture rich when the finish was applied. Eric, did you have a moisture meter reading on the cedar before you built the chair?

Beautiful workmanship, by the way. I looked at your Projects page.



-- " his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View Eric's profile


221 posts in 2538 days

#5 posted 12-30-2013 02:04 AM

No moisture meter. I purchased the cedar in the summer months right from the homecenter…. nothing fancy.

-- Eric

View gfadvm's profile


14940 posts in 2717 days

#6 posted 12-30-2013 02:04 AM

I suspect that is Spar Urethane rather than true Spar Varnish as I have had the exact same experience with MinWax Spar Urethane on chairs in my barn. They haven’t ever gotten wet but are exposed to direct sun for most of the afternoon.

True Spar Varnish is a different breed of finish that I have no personal experience with but am told that it is used in marine applications.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View pintodeluxe's profile


5706 posts in 2840 days

#7 posted 12-30-2013 02:04 AM

I won’t build outdoor wood furniture for this reason.

I have not had good luck with spar finish. We used it on a door many years ago. Someone taped a mail notice on the front door with scotch tape. When we removed the tape it peeled the finish right off.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View Eric's profile


221 posts in 2538 days

#8 posted 12-30-2013 02:09 AM

Just checked the old can. Yes. It is Varathane Spar Urethane. The chairs sit out year-round.

-- Eric

View Loren's profile


10476 posts in 3675 days

#9 posted 12-30-2013 02:18 AM

My folks have a cabin in the mountains. 2 doors down there
is another the owner finishes with spar varnish. The side
that gets the sun gets devastated while the shady sides
hold up a lot better. It snows up there too, which
only makes the situation worse I imagine. The place
looks gorgeous when the varnish is not peeling off.

Every year on a boat I think you go over every varnished
surface with a wire brush, sand and recoat. The salt
air is the worst, combined with the sun hitting it.

View Dusty56's profile


11819 posts in 3715 days

#10 posted 12-30-2013 02:46 AM

Just part of an article about “spar” varnishes and urethanes:

”Now, lets take a look at the marine varnish pretenders—the so-called “spar varnish” made from linseed oil and urethane resin. “Spar Urethane” varnish should be avoided in any exterior application in which even moderate exposure to direct sunlight is likely. We need look no further than the properties of varnish made from urethane resin (polyurethane) to understand why. Urethane resin varnishes suffer two weaknesses that have direct bearing on varnish used in exterior applications in general, and marine applications in particular.

First, urethane resin is highly subject to UV damage. Polyurethane will begin to yellow, develop hair-line cracks, and loose adhesion with the wood very quickly in a full-sun environment. Soon thereafter it will begin to flake and peel from the surface. The more popular spar urethane varnishes can be expected to completely fail in as little as a single season in a full-sun environment. Even in moderate sun they are likely to last no more than a couple of seasons.”

-- I'm absolutely positive that I couldn't be more uncertain!

View distrbd's profile


2252 posts in 2473 days

#11 posted 12-30-2013 03:53 AM

Mr Lee Barker,thank you for pointing out my mistake of using the wrong terminology,my point was that it looked like the moisture content of wood was high and the spar varnish might have trapped it in the wood in other words it did not release the moisture it had taken in,like you said”the wood may have been moisture rich when the finish was applied.”
Loren I had no idea direct sunlight would destroy the spar varnish,I had heard wood surfaces with 2 part epoxy should not be left under direct sunlight,but never knew that about spar varnish.

-- Ken from Ontario, Canada

View Eric's profile


221 posts in 2538 days

#12 posted 12-30-2013 05:05 AM

Dusty. You are definitely describing what I am seeing.

Does anyone have a good alternative recommendation for cedar outdoor year-round?


-- Eric

View jumbojack's profile


1677 posts in 2651 days

#13 posted 12-30-2013 05:30 AM

were these fence boards?

-- Made in America, with American made tools....Shopsmith

View Loren's profile


10476 posts in 3675 days

#14 posted 12-30-2013 06:12 AM


View shipwright's profile


7992 posts in 2825 days

#15 posted 12-30-2013 06:31 AM

-Red Cedar is notorious for not taking finishes well even paint. It’s natural oils just don’t like it.
-UV rays actually attack and degrade the surface layer of wood cells under a clear finish and cause adhesion failure.
-All bright finishes on boats are an ongoing maintenance situation.

Things that have worked for me are:

1)With red or yellow cedar and with oily wood in general you can stabilize the surface by applying a coat or two of S1 epoxy sealer (System Three). It has a high level of lacquer thinner and can penetrate and seal the surface. follow that with your high UV resistant clear finish. Revisit the topcoat annually…. sand , repair, re-coat.

2) Cetol (Sikkens)

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees.

showing 1 through 15 of 25 replies

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