# I think I screwed up... Spar Urethane on an outdoor table



## GregTP (Oct 26, 2015)

hello all, I think I might have screwed up. Working on an outdoor table for my covered deck. The top is a lovely and hard to come by (at least in my neck of the woods) 35" wide double live edge slab of dawn redwood. After flattening the slab and sanding I am up to 4 coats of Minwax spar urethane, recommended from a good friend of the family who has been running a high end cabinet and furniture business for 40 years (also a sawyer and where I got the 10' long slab for FREE!). He has made several tables and outdoor bar tops out of the same stock and swears by the minwax finish. The intended location of the table is fully covered, 18'x13' deck so it should have no more that 2-3 hours of sunlight per day.

I should have done my research but after looking for some in-between coats advise on the forum I am seeing nothing but horror stories form this product. Is there anything I can do now, short of sanding it all off and getting some proper spar varnish? My thought was, is it possible to sand and finish the last coat of spar that I have on there now and switch to the proper marine stuff? Would that protect the urethane and hopefully prevent the splitting and peeling, or will it happen anyway?


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## wapakfred (Jul 29, 2011)

I don't think so. I would strip it all off and start over. Anything you put on top of it will be dependent on the substrate finish.


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## Yonak (Mar 27, 2014)

A cursory search for Minwax spar urethane on these pages didn't show the horror stories you're talking about. What were the problems reported ? Were the application procedures the same as yours and for usage in the same conditions ?


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## ric53 (Mar 29, 2014)

I have used Minwax spar urethane in the past and have had no issues. What issues are you expecting since your photo shows none.


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## GregTP (Oct 26, 2015)

Thanks Fred, that is largely what I suspected but you can always hope for a miracle cure!

Yonak, i found most of the issues under the finishing forum, I searched Spar urethane in the toolbar. Most were similar stories although the worst of them seemed to be one or two coats that were in direct, all day sunlight. Looks like after a season or two the urethane discolors, flakes, and peels.

The advise I got was 6-8 thick coats, wet sanding in between with 400 grit paper.

I think my solution is going to be sticking with what I have on there now and making it an indoor table, I have two more smaller slabs that would be perfect as end tables so I think I will just make a set and replace the cheap tables I have in the living room.


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## splintergroup (Jan 20, 2015)

I've had the Minwax Spar Varnish flake after two years outdoors, went with Epifanies Spar Varnish (Jamestown Distributors) and it is still fine after five years.

Any surface film type finish will fail outdoors eventually. The key is flexibility (hence the 'spar' formula) and the UV protection.

Penetrating oil finishes do well (Penofin for example) if regularly re-applied.

You can sand the old stuff away and apply something else or just leave it be and see what happens. I'd refinish at the first hints of failure however, that slab is beauteous!


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## ThomasChippendale (Nov 6, 2015)

The problems related on the internet could be caused by improper application, Minwax would be out of business if they produced sub-standard products.

The main mistake I have seen is applying too few coats. To endure outdoor exposure, one needs a thick film. I would keep the 4 coats already applied and continue with a better quality Spar varnish such as Epiphane or one of the Interlux products available from marine supply stores. Apply as thick a coat as possible, to the edge of having runs and sand between well dried coats with 220 grit. Whipe with mineral spirits as a final wash between coats and put no less than 8 coats total, adding a fresh coat every season.

45 years of boating experience varnishing teak and mahogany.


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## wapakfred (Jul 29, 2011)

I'll somewhat disagree with your assessment. Anything with urethane resins in it is going to fail outdoors, they just don't work well in that application. All of the quality true marine varnishes are based on a different resin, usually alkyd. I am humbled by your experience, but I'd bet it was always working with the good finishes….not the crap like Helmsman.


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## wormil (Nov 19, 2011)

If it's for use under a covered deck then it's only semi outdoors and since there isn't actually a problem I think you'd be foolish to sand it off and start over. Also the internet has a horror story for everything. If you make every decision based on internet advice, every decision you make will be wrong according to someone.


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## ThomasChippendale (Nov 6, 2015)

I must be mixing-up Urethane with Polyurethane. I have always used the real stuff, oil based, alkyds and Polyurethanes so it has always been durable, and pretty.

http://www.defender.com/product.jsp?path=-1|2200442|2200478&id=2108231
http://www.jamestowndistributors.com/userportal/document.do?docId=309#CP313670
http://www.westmarine.com/buy/bristol--bristol-amber-urethane-finish--P003692852


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## GregTP (Oct 26, 2015)

Thanks guys,
Risk M I agree that the internet is full of the bad, people don't get as excited over a product that does what it says it does.


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## bondogaposis (Dec 18, 2011)

I wouldn't do anything until, when and if it fails.


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## kelvancra (May 4, 2010)

I'm with Bondo - it aint broke [yet], so don't fix it.

For reference, one of the big differences between interior and exterior, U.V. protection aside, is the amount of oil used in the product. More oil means less durability, but more flexibility. More flexibility means more tolerance of dimensional shifts in the wood.

One thing you can do to crank of the life is, make sure EVERY surface is sealed. If you haven't already, think about applying highly thinned oil based poly to the underside. Initially, thin as much as fifty percent. As long as the wood takes the thinned finish, keep adding. It may soak for an hour and be ready for more. Then two hours…........

A big piece of, essentially, plastic wood cannot gain or lose moisture, so will not expand and contract as its counterpart. This could add years to the longevity of your work. It did to the one I did and which sat in front of a fire place for decades.


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## gfadvm (Jan 13, 2011)

Sunlight exposure (not water) has always caused MinWax Spar Urethane to crack and peel in ALL outdoor projects I have used it on. I like/use this finish a lot (just not where it will be exposed to direct sunlight).


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## kelvancra (May 4, 2010)

I forgot an important detail to my post, above:

You can add flex to cheap surface coats, like Varithane or MinWax, by adding more hardening oil. You might have to experiment, but you could play with trying, for example, twenty-five percent more oil. If needed, you could also add thinner, as needed.

Again, more flex will allow the finish to hold up better to dimensional shifts due to gain and loss of moisture.

Keep in mind, even the best finish can be knocked off the wood if moisture can get behind it.


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## dhazelton (Feb 11, 2012)

That looks gorgeous. Use it like it is and recoat down the road if it fails. You could always put a screen of some type hanging from the edge of the overhang so the sun doesn't beat on it.


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## GregTP (Oct 26, 2015)

So my end solution was to keep the spar urethane and make this an indoor table. I didnt seal the bottom of the table because this was not kiln dried wood and I wanted it to be able to breathe, or more accurately, I wanted somewhere for the trapped moisture to go other than through the finish.

I suffered for a long time trying to get the final coat completed. I ended up dry sanding with 220 paper, polishing with 00 steel wool, then sanding with 1200 grit and mineral oil, then finally polishing with silicone free automotive polis









hing compound. I had two "final coats" as I learned an important lesson about letting the last coat cure before trying to polish it…

Finished pictures below


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## Dj1225 (Apr 27, 2012)

I used this on a walnut table that is on my covered porch. It gets very little rain and no direct sun and it appears to look as it did the very first day which is over 5 years ago. I also sprayed two coats on outdoor chairs that are in direct contact with the elements. It has not held up well. I am actually disassembling the chairs to sand and refinish. Most likely I did not put enough coats on the chairs. If you are under cover it should be fine. Just watch and re apply at the first signs of wear.


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## GregTP (Oct 26, 2015)

Table update.

After a few weeks in the house, the crack that runs the length of the top (through those big knots in the picture above) widened significantly; maybe 1/4". So I took the top off and back out to the shop. I had to belt sand the middle of the table down to get both sides of the crack flat again then put four butterflies in. I should have done it to begin with and I think I knew that then but I had already spent too much time on this project and was getting anxious to get it finished. A lesson well learned I guess.

I made the butterflies out of cherry, I'm hoping after they age they will compliment the reds and browns nicely. I had to pour in quite a bit of epoxy to refill the crack and will get to work sanding and smoothing that later this week
I covered the butterflies in painters tape just to keep the epoxy out of the grain. I will have to end up stripping the spar urethane finish down all the way and restarting. I think I will go with a standard poly finish this go-round since I've decided to keep this as an indoor table.


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## AlaskaGuy (Jan 29, 2012)

http://askhlm.com/Articles/ArticleViewPage/tabid/75/ArticleId/1/Marine-Varnish.aspx


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## GregTP (Oct 26, 2015)

That was very informative, thanks alaskaguy!


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## JBrow (Nov 18, 2015)

GregTP,

Although you solved your outdoor furniture finishing problem by making that beautiful table a piece of family room furniture, I thought I would add my experience with outdoor tables for anyone who might stumble on this thread in the future. By the way, moving the table indoors allows you to enjoy it year round rather than just in the summertime (if you are like me and live in a 4 season climate of the mid-west). Kudos on the butterflies; excellent craftsmanship!

I too have a covered patio. It faces west so on a sunny day, 2-3 hours of setting sunlight invades the patio. Also, windblown rain enters the patio space.

I had metal frames for an end table and a coffee table. I painted the frames black and constructed tops from red oak. I used Plain Sawn lumber, not the best for outdoor projects. But that was what I had. I applied 5 coats of Helmsman Spar Varnish semi-gloss polyurethane I think (don't exactly remember the number of coats), screwed the tops to the frames, and put them on the patio. Even though these tables were store in a shed in the winter, within two years, the tops failed. The both table tops cupped badly. The finish seemed fine, though a little dull.

Undaunted, I went back into the shop and glued up two more table tops from red oak, again from Plain Sawn lumber. However, this time I used the router and a core box bit to route groves on the bottom of the table tops, from one end to the other parallel with the grain. I spaced the groves about 3" apart (center to center) and they were about ¼" deep. The table tops are 3/4" thick. After sanding, I applied 5 coats of Helmsman Spar Varnish, semi-gloss polyurethane. The tables have completed their second summer of duty. The tops are stable and holding up well.

As far as the durability of the finish, it is holding up fine, although the glossiness has faded. I will probably add another coat or two this year after a light sanding.

I think what happened on the original tops that cupped is that there was not enough finish to prevent moisture from entering the tops (if it is even possible to apply enough finish to achieve this result). Moisture entered the tops, caused expansion that overwhelmed the provision I had made for expansion and contraction. The moisture caused the wood fibers to swell and without room for lateral expansion, the tops expanded upward forming the cup. I counted on the 5 coats of finish to keep moisture content under control. Obviously I was wrong.


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## Unknowncraftsman (Jun 23, 2013)

I thought Gregs table very nice,great idea keeping it inside.
I would like to share a finish I have had good sucess with.Just apply 3 or more full coats to all sides it's very easy to use and water based.It must have Uv blockers holds up outside just like clear paint.


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## OSU55 (Dec 14, 2012)

An exterior base 4 or 5 oil based paint will dry clear and provide about as good of protection as you can get.


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## GregTP (Oct 26, 2015)

Thanks guys, sounds like good advice all around.


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## shampeon (Jun 3, 2012)

JBrow: I think the red oak contributed to your problem. The end grain on red oak is porous, compared to white oak, where the pores are filled with tyloses. That's why white oak is used for barrels, ships, and outdoor furniture.


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## eflanders (May 2, 2013)

Based on my wooden boat building experience, spar varnish issues are usually caused by improper application. Sunlight/UV is the destroyer of most clear finishes. Spar varnishes have a UV inhibitor added to them to slow down the degradation, but even the best spar varnish needs to get reapplied every few years. How often? Well that all depends upon the exposure amount, the number of base coats used and the original wood surface texture. Most boat builders will use At Least 4 coats at a bare minimum and the quality builders in certain environments will do doable that as a minimum. Even when you use an epoxy as your finish base coat, you will still need to top coat it with the 4 coats of Spar Varnish. But some woods are more suited to outdoor, water environments than others as we all know. What many folks don't know that red oak is really bad in an outdoor environment. White oak is what some boat builders use instead as it will not readily absorb water like the red oak will.


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## BurlyBob (Mar 13, 2012)

I'll leave all the advice about finishes to others. Let me just say that is a beautiful piece of wood and it t turned into a beautiful coffee table. I think your decision to keep it indoors was the right one. I wish I could find a slab like that.


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## JBrow (Nov 18, 2015)

shampeon & eflanders,

I agree with both of you; that there are generally better choices for outdoor projects than red oak. Its huge pores soak up moisture like sponge, which I found out on my original table tops. But if properly done, it can survive at outdoor environment. But anyone buying lumber for a specific outdoor would do well to heed your advice - and avoid red oak.

In my case, some time ago, I purchase 3000 bf of red oak at an incredibly low price. Now what on earth am I going to do with all that oak? I am slowly working through that pile. In addition to the failed table tops and the table tops that remain in service, I constructed an outdoor backyard fence.

The red oak fence is a picket fence constructed in 2009 with lap joints and round edges and sloped surfaces. The only unprotected end grain is on the bottom rail of the fence, where the pickets terminate. The gate hinge is also constructed like a piano hinge from oak. It has held up surprisingly well, with minimal checking.

But the fence has been a maintenance nightmare. I initially coated all surfaces before assembly with 2 coats of Sikkens SDR, a product designed for no-sand reapplications. It is a penetrating finish, rather than a film forming finish. Then every year, I hand sanded the spots, especially on the top rail, where the finish failed, spot applied finish on the sanded area and then applied a fresh coat on all exposed surfaces. This 3 day project was not much fun.

Last spring, after speaking with Sikkens, I changed products to Sikkens Proluxe Cetol 1 RE Exterior Clear Stain. That required removing the prior finish and applying two coats of the Cetol 1 - a 3 week project. That finish seems to be holding up better, but I am sure I will be out there this spring with sand paper and more stain. But while the maintenance is ugly, the fence is pretty.

Conclusion. Yes, for outdoor projects, avoid red oak unless you have tons of it, pay close attention to construction methods, and be prepared for frequent and never ending maintenance.


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## GregTP (Oct 26, 2015)

Thanks BurlyBob. I still have three smaller slabs (about 2 ft long by 30ish inches wide) that i unfortunately cut from the remaining 6ft of original slab. My first design called for using the smaller slabs as live edge legs with a large arch cut out to create separate feet and remove some of the bulk. But after I cut all the parts (I didn't cut the arches) and set them up as a mock it looked like Fred Flintstones's table… So I built a simple base out of poplar and I will use the other three slabs to make matching end tables eventually.

The guy who brought my friend this wood wanted him to cut it into chunks so he could split it for firewood!!!! Thank goodness for a well trained eye.


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## Wondermutt (Jan 21, 2016)

I have a table much like your and was not sure of the topcoat. So I went to my local auto parts store and bought some carnuba car wax. Put on three coats followed by a light buffing with a orbital buffer, and so far so good. No issues with fading nor peeling.

Good Luck

WM


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## TarHeelz (Sep 13, 2012)

Yes. This finish will, if left alone exposed to sunlight, eventually fail.

Unfortunately, every finish, if left alone outside exposed to sunlight, will eventually fail.

The key to your future happiness is maintenance. You maintain the exterior of your house by cleaning and painting it periodically. You maintain your deck by cleaning and staining or sealing it periodically. If you apply the same thinking to this beautiful table, you should be quite pleased.


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## GregTP (Oct 26, 2015)

So I finally finished this project, hopefully for the last time . We are in the middle of buying a new home and selling our current one so my shop time has been pretty severely limited recently.

I fixed the crack with four butterflies as mentioned above. I ended up taking a bit of gamble in that I didn't strip the entire top down (see photos above). Four coats of brushed on Spar to build up a bit faster and then 10 coats of sprayed Spar to finish it off. It turned out nice and is now back in the house. Sorry the images a bit rough, low light first thing in the morning! The only thing I'm not completely happy with is the stock I chose for the butterflies (cherry), it might have been nicer with something that had a bit more interest like some spalted maple but you live and learn!


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## Jockstrap (Jan 18, 2019)

Hello
I've had some problems getting the urethane to dry on a project ( outdoor wooden bench).
It never seems to cure properly. My workshop is outdoors and unheated until I turn the heater on.
Living in the Pacific Northwest the weather is often wet and cool and occasionally freezes.
I'm hoping…fingers and toes crossed…that it's still usable and that the problem is something else.
Any thoughts would be appreciated.
Thanks


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