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Discussion Starter · #1 ·
I just built a sprial stair handrail out of mahogany. It is for an exterior set of steps that is under a cantilivered roof above. It does not get directly hit by the elements but is subject to being outside. We would like to stain it to closer match existing ipe stair treads. My question is what would be the best clear coat for this application?
 

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Old School
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I've tried all kinds of "spar" varnishes. The problem I've found is that they will need refinishing after they dry out, crystallize and get flakey. Refinishing is a PITA and requires a lot of sanding and the reapplication process. Most of the top brands direct a multiple coat finish. For example Interlux Schooner requires 5-6 coats.

I've gone to the oil type finish, using pure Tung oil, with and without wax. It maintains easier and to refinish is much simpler. I think it looks better than the "film" type finishes.
 

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I used General Finishes Arm-R-Seal (oil + urethane resin from Rockler) to finish a mahogany tree swing last summer. My thinking was that the oil would make refinishing easier - if needed, and I hoped to get 5 years out of the first application. The swing collects snow in the winter, so I had to redo it this spring (a couple spots got pale). All I had to do was wipe a new coat on it. No sanding. It looks great for now. But the jury is still out.
Dave
 

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Polyurethane

would be my suggestion.

Ed
 

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Discussion Starter · #8 ·
Well, I have been discussing this with the painter on the job and he is saying to use "pennafin" rosewood oil? My only concern with this is the way I built this handrail was by laminating 1/8" strips of mahgany together and screwing the inside wraps together then laminating the outside with glue only. Will the oil delaminate the strips or am I safe with this. My other idea is to spray it with a waterbased polyurathane, with I have been using for all my interior applications.
 

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I use to preach Minwax's Helmsman Spar Urethane for exterior UV protection on woods you wanted to keep the fade from happening. Until quite recently in fact. But I have had some samples all turn south and I mean all at once.

I only put sample UV coats on eastern red cedar and bois d arc (osage) because they are indigenous woods that have alot of beautiful color I hate to see fade out from the sun.

The Helmsman Spar is the best thing I have found to prolong the inevitable, but as cab'man points out, it is not a question of if, but when. the direct sunlight is going to break it down eventually it is a matter of physics. I am glad it broke down when it did because iwas actually going to spray our entire exterior with the stuff. YIKES! What a mistake that would have been. The reapplication would have been a nightmare. It would have to have been stripped and prepped before recovering with something.

I hope one day some genius will come up with something that will prevent color loss but probably not in our lifetimes. Persoanlly I would not use anything like a polyurethane in your application whatsoever. I would use something that takes a brightener at most when it comes time to refinish, and it comes time alot sooner than you think.

Take cabinetmans advice and stay away from the polyurethanes in this application. Just my advice based on my experience, other posters experiences are just as valid even though they are not the same as mine.
 

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Discussion Starter · #10 ·
I will take a pic of the handrail at my shop and the jobsite where it will be installed. There is no direct contact with sun, rain, snow, ect. Just the outside weather changes and on rare occasion wind driven rain or overspray from the hose from cleaning the home. Thanks for all the advice so far...
 

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Rain won't hurt it from the outside, but the moisture trying to get released from the inside of the wood is what eventually comes through the film.

No direct sunlight is good but if the wood faces a wider swing of moisture release and absorption than the the film can allow, that is what breaks it down.

This is not me trying to sound like I am a guru I am simply repeating what a chemist at DOW chemical tried to drive into my little pea brain one time recently when I was lucky enough to get some of his time over the phone. As I have said I am serious about trying to find a magic bullet for color preservation I just don't think it will happen in our lifetime if ever.

I have also spoken with chemists at Minwax, Deft, others more than I can remember right offhand, and a real small company in Seattle who is doing research on whale oil by-products (totally un-PC especially in Seattle) for siding sealers but I have yet to speak with a single credible soul who says they can offer a color preservative that can withstand both UV and moisture attacks for any reasonable length of time.

Please let me know if you do.
 

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check out www.Bristolfinish.com for a catalyzed acrylic urethane that's used on top end yachts.
I've used this stuff, and find it to be the best so far. Better than ICA 2k, way better than Helmsman, and other standard marine varnishes.
 
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