outdoor finish on white oak bench

[Michael MacDonald]

I have built a bench for my front porch with white oak (heavy sucker). I had planned on finishing it with Watco danish oil in a medium walnut tint... and then spraying spar varnish from Helmsmans. So I was researching that approach to get some feel-good confirmation. uh oh.

I have learned from some seemingly authoritative web sites that spar varnish (and helmsmans in particular) is not so great: it is soft, it doesn't protect against moisture well, and the UV protection wears out eventually. The real feature of spar varnish seems to be that the softness of the finish allows for wood movement (e..g stress on masts and yard arms on sailboats), but that the other features one typically attributes to it (moisture protection, UV protection) aren't really there. Funny, because most recommendation specify spar varnish (woodwhisper, this forum, and many others)... seems like conventional wisdom maybe is off-kilter? or am I just personally off-kilter?

here is the main reference that seems to buck conventional wisdom and has thrown me off course: http://www.hardwoodlumberandmore.com/Hardwood/Finishing/MarineVarnish.html

So now what? I really like the way the danish oil made the white oak grain pop on my test pieces... I would like to stick with that as the first treatment. Watco makes an external oil as well, which is nice--but only in Natural. (Actually, the final tint is not so far off from the med walnut.) But why do I suspect those writers at the web site reference above would dismiss it out of hand?

So I am considering a coat of the danish oil, then after a day trying a coat or two or three of the Watco external oil. Don't even know if that makes sense--will the external oil coat penetrate enough to do any good?

Any other suggestions? I am really lost at this point... rug completely pulled out from under me. derailed and bewildered.

just for kicks... here is dry assembly from a few weeks ago... bottom and lid are missing, and I hadn't yet finished turning the legs:
http://i953.photobucket.com/albums/ae20/miwmacdo/DSCF0876.jpg

[Scott Holmes]

The website you reference is Steve Mickley, a friend of mine. I've never seen or heard him blunder when it comes to answering finishing questions...he knows his stuff. If he doesn't know an answer, he'll tell you so. I strive to be the same...

"Exterior oil" from Watco is Marketing hype. Oil only finishes provide very little protection.

Spar and marine varnishes are different. Both are exterior meaning they are what is called long-oil varnish, softer, and more flexible, also LESS waterproof because they are softer and more flexible.

Marine varnishes have UV inhibitors in them; spar not so much.

Polyurethane resin varnishes (poly is only a type of varnish, not a type of finish by itself) is highly susecptible to UV damage. WHY would a manufacturer make an exterior finish with poly? you ask... PROFIT ! Poly varnish is very cheap to make compared to the other varnishes.

The best marine varnishes are available at boat supply houses or marinas. Don't let the $40+ per quart scare you, it's worth every penny. It will still need to be recoated every 5-7 years. No stripping required.

Here in Houston, Helmsmans marine (poly) wont last a year outside; and it gets chaulky so it must be stripped before it can be recoated. Wood below is often damaged by the UV.

[Michael MacDonald]

Well, I hope I didn't come off as questioning Steve M... I guess I am just surprised that abrasion and water resistance are not part of the equation... I certainly don't question the science behind why that is the case. The article linked in the OP was the first time I had ever heard marine varnish criticized for my intended use... so it was a reality check. I had originally come across marine varnish as a recommendation without also hearing some of the trade-offs--this is what put me off balance.

I had read that urethane yellows and cracks with UV exposure... I don't want that.

In the end, the bench will sit on a covered porch that gets afternoon sun. So water protection is probably not as critical as UV protection. And I don't ever want to have to sand this thing again.

After getting some of the names of better non-urethane products from various posts and articles--Epifanes and Waterlox Marine, I started to research and only found high gloss. Not great for me. I found that Sikkens Door&Window and Certol Marine have satin products, and I plan to order one of those.

not sure if it is still worthwhile to put the danish oil down first... it looked good on my test scraps, but then I was using helmsmans on top. don't know if it adds any value--the sikkens products already have an amber tint, I think.

I have to say, I get a kick out of milling all the components, but time slows down when it is time to sand and finish.

[Howard Acheson]

not sure if it is still worthwhile to put the danish oil down first... it looked good on my test scraps, but then I was using helmsmans on top. don't know if it adds any value--the sikkens products already have an amber tint, I think.



You can still use the Watco as a coloring agent and overcoat it with another oil based true marine finish. Watco Danish oil is just a mixture of boiled linseed oil and very small amount of varnrish. Other than their Natural, a small amount of stain is added to give you the color.

But, let me make a point, ANY finish, even the best true marine finish containing UV inhibitors, will lose its effectiveness as it absorbs UV. Approximately annually, you will notice that the finish is becoming cloudy. At this point it must be lightly sanded with 220 paper and a couple of new coats of finish applied. This maintenance is the only way to maintain the long term appearance of the item.

BTW, marine finishing professionals know about the deficiencies of consumer grade exterior finishes. You will never find those products being used in a boatyard or by a yacht builder. Interior short oil varnishes are used where ever the surface could be walked on or otherwise abused. Long oil exterior varnishes are used for spars and such that are subjected to rapidly changing environmental conditions. These surfaces do not require much abrasion protection. Unfortunately, most amateur finishers only know what they see from suppliers of consumer products and those products are more subject to marketing than to performance.

[Michael MacDonald]

great... that is helpful. Thanks Scott and Howie... after resetting my expectations on the marine varnish, I feel a little better... after weeks of noodling over these choices with some level of stree, I finally think I am making a non-stupid choice... really, that is all I ask for. Not a very high barre.