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

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Forum topic by GregTP posted 11-09-2015 01:33 PM 1848 views 0 times favorited 32 replies Add to Favorites Watch
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GregTP

51 posts in 406 days


11-09-2015 01:33 PM

Topic tags/keywords: spar urethane outdoor furniture live edge table finishing

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?

-- From exercise machine warning label: "Step ladders can cause injury and even death; the ROM machine is more dangerous than a stepladder"


32 replies so far

View Fred Hargis's profile

Fred Hargis

3935 posts in 1956 days


#1 posted 11-09-2015 02:59 PM

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.

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

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Yonak

979 posts in 983 days


#2 posted 11-09-2015 03:49 PM

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 ?

View ric53's profile

ric53

147 posts in 982 days


#3 posted 11-09-2015 04:06 PM

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

-- Ric, Mazomanie

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GregTP

51 posts in 406 days


#4 posted 11-09-2015 04:10 PM

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.

-- From exercise machine warning label: "Step ladders can cause injury and even death; the ROM machine is more dangerous than a stepladder"

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splintergroup

827 posts in 685 days


#5 posted 11-10-2015 03:25 PM

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

244 posts in 395 days


#6 posted 11-10-2015 03:53 PM

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.

-- PJ

View Fred Hargis's profile

Fred Hargis

3935 posts in 1956 days


#7 posted 11-10-2015 04:05 PM

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.

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

View Rick M's profile

Rick M

7910 posts in 1843 days


#8 posted 11-10-2015 07:23 PM

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.

-- http://thewoodknack.blogspot.com/

View ThomasChippendale's profile

ThomasChippendale

244 posts in 395 days


#9 posted 11-10-2015 08:02 PM

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

-- PJ

View GregTP's profile

GregTP

51 posts in 406 days


#10 posted 11-10-2015 09:25 PM

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.

-- From exercise machine warning label: "Step ladders can cause injury and even death; the ROM machine is more dangerous than a stepladder"

View bondogaposis's profile (online now)

bondogaposis

4027 posts in 1814 days


#11 posted 11-10-2015 09:33 PM

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

-- Bondo Gaposis

View Kelly's profile

Kelly

1113 posts in 2407 days


#12 posted 11-10-2015 09:44 PM

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.

View gfadvm's profile

gfadvm

14940 posts in 2153 days


#13 posted 11-16-2015 01:59 AM

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).

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

View Kelly's profile

Kelly

1113 posts in 2407 days


#14 posted 11-20-2015 12:08 AM

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.

View dhazelton's profile

dhazelton

2324 posts in 1759 days


#15 posted 11-20-2015 12:49 AM

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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