I posted this under Finishing last week and got no responses in the two or three hours before it was pushed under the electronic carpet. So I am taking the liberty of posting it here, in hopes someone might have a suggestion and might have just missed it. If you saw it and ignored it, I apologize for posting it again.
I’ve built a porch swing from mahagany. It will be on a covered porch, so it will get wet only from blown rain, though it will get a fair amount of sun. Any ideas on an appropriate finish? None?
Replies
Hi Mark:
IMHO good ole spar varnish is the only way to go. An exterior piece will typically (I don't know where you live?) move more than an interior piece even if "covered" as is your swing. This type of varnish stays more flexible than even an exterior grade poly. Spar varnish is also your best protection from the UV rays that your swing will get. Hope this helps.
It does help. Thank you very much.
I went through the same dilema a couple of weeks ago on how to finish a couple of adirondack chairs I made out of spanish cedar. The way I understood it. If you go with the spar one day you will have to refinish it which entails sanding of all of the previous finish. If you go with an oil you will probably want to renew it every year. I chose to do nothing and just let them turn a silvery gray, and so far they look great. My thinking was if I don't like the way they look or are holding up in a few yrs I can always sand them down and put a finish on them. FWIW
Mark
I have mahogany(a lot of it) on a sailboat that stays in the water (outside) all the time and I use varnish. Two aspects of varnish and mahogany: 1) varnish can be redone periodically WITHOUT sanding or stripping it all off each time you recoat. The key is to recoat (after a light sanding ) before the varnish breaks (wears through)and you get bare wood. I have been doing this for several years with no problem. 2) Mahogany can bleach out and end up looking blonde where there is a lot of exposure to sun. Different pieces of wood will "fade" differently but direct sunlight for a few years can result in blonde mahagony. Not bad looking but sometimes unexpected.
Do you re-coat every year?
Yes, I recoat every year. Actually, to assure I stay ahead of it I put on about 3 coats twice a year. Keep in mind I am in S. Carolina and we get a loy of direct sun. For porch furniture not in the sun constantly, not so much recoat would do.
Thank you for the response. I really would prefer to leave the piece unfinished, but on the other hand I'd like to protect it if the protection is going to be meaningful and my wife, for whom this is a birthday present, says she wants it finished and I have to calibrate how hard to argue with her. Shall I suggest that she finish it? God, that makes me laugh.
It makes me laugh even harder when they suggest that they'll finish it.
Sun, not water is the enemy here. Because the sun's UV rays can get through the clear finish, it breaks down the surface of the wood, causing the varnish to flake. Spar varnish with UV inhibitors slows, but does not stop this process. A pigmented finish slows the process even more. Paint would prevent UV degredation the best, but defeats your purpose. There's a marine product called Cetol that has a lot of pigment, but still lets some grain show through. I'm not crazy about how it looks, but it's a reasonable compromise between looks and eternal sanding. I'd steer clear of oil, it can become gummy when exposed to humidity, something that would be very undesirable in a chair. One last option. Make a cover for the chair and keep it covered when not in use. It will keep the sun off and reduce your maintenence.
PS, if you do go with Varnish, get it from a marine store. Get a good brand. Epiphanes comes to mind.....
Thanks. I think you're right about the UV being the worst enemy, and I have thought about the cover. Not sure my wife would go for it, because for her having the swing out there "looking nice" is probably 85% of the reason for having it.
We use Epiphane, from Jamestown Distributors, on our front office door, and recoat every 2 years. It is a Southern exposure in Center City, Philadelphia. No pix, but we started with a pigmented stain, and touch it up as needed before applying 2 coats.
On my home 3 years ago I built and installed 3 sets of mahogany french storm doors, pix below, which were "stained" with potassium dichromate (applied outside, of course), and then 2 or 3 coats of a good spar varnish, McCloskeys I think, and have not touched them since. The exposure on the set pictured is Western. I am sure recoating will be required, but it is not as bad as I thought it would be.
That's good information, and nice-looking doors. Thanks.
Penofin.
You win the award for brevity.
What's penofin?
An exterior grade PENotrating Oil FINinsh - hence the name Penofin.
As opposed to nilns for peNetratIng oiL fiNiSh.
You think it's equal to or better than spar varnish?
Really two different products. If you want the ultimate in film finishes, you can't beat spar varnish, but it's not repairable. It's strip and refinish.
But does the other stuff provide the same level of UV protection and resistance to moisture changes? I don't really care about a film finish per se - I'm not trying to protect the piece from scratches or nicks.
Oh, heck Mark I don't really know. I know that I've used it in lieu of a film forming finish as the client didn't want one. The client has reapplied the stuff every year, the door has not warped (it's not located in a deep porch, nor is there a substantial overhang). I would have to assume that a thick varnish, and spar certainly is that, provides the ultimate in protection for wood exposed to the elements. It has it's place and you have to give the devil his due. If there is no objection to a profound film finish, then I'd use the spar in a heartbeat. At some point it will have to be stripped (mechanically or chemically) and completely re-done. The Penofin in simply refreshed from time to time. It has UV inhibitors, but no product can completely stop UV graying of wood. They will all change color over time if they're outdoors. The only way to get the old color back is with a belt sander with 60 grit.
That said, I wouldn't rely on any finish to inhibit excess movement in an outdoor application. Rather, I would specify quartersawn or riftsawn stuff. I have built a few entry doors in residential and ecclesiastical settings and have never used anything but these two (at least in recent memory). I don't need no stinking badges, and I don't need a call back. It's the best or nuttin' at all with 'ole Charlie.
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