Shellac For Oak Window Casing?

I have a north-facing bathroom window that gets a fair amount of condensation in the winter. I need to replace the casing due to damage, plus I need to paint the room.
Rather than going with painted casing, I was planning on using oak. My preference is always clear shellac rather than poly, since the latter tends to yellow.
Will shellac have any problem holding up to that environment? I guess I can always try it, and if it doesn't work out, just sand it off and do poly.
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I love shellac but I don't think it is right for this application. I would go with white oak and seal it with a water based poly which will have less of a yellowish cast than oil based. I would choose to go with an exterior grade poly with UV protection. My two cents.

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Painted is almost always the best for harsher environments. You have to balance wear with appearance, and only you can do that.

Keep in mind that shellac on its own has very little resistance to water. It will discolor, and in an area where it will be repeated exposed to water will allow the wood underneath it to discolor. And while shellac doesn't yellow as fast as poly, it will certainly discolor.

Ditto all above for you concerns with UV resistance when using shellac. While a good exterior grade poly has UV inhibitors, shellac has none. You will be surprised how rapidly the finish will degrade with exposure to sun AND water. This application is not shellac's strong suit.
And if you leave the shellac alone long enough to allow the underlying material to discolor, sanding off the shellac an putting on some poly will look like a poor refinishing job, depending on how long you let it go.
Oak can be problematic in its finishing as it is. The large tubules in oak require a finish that is elastic enough to span its texture without sacrificing its strength. To get that much shellac on a project, you will probably need to get to about 6 mil or so, when dried. (That can be a lot of effort!)
Remember that NOT sealing the tubules closed or using a not-to-elastic finish will result in a quick finish failure. Even more so in a wet, sunny exposure area like you have.
Modern finishes are formulated so well these days you have a lot options. You could use some of the spar type vanishes, polys, etc., which will all eventually yellow, but provide good service.
You can apply a polyurethane conversion lacquer which will provide great service and not yellow rapidly. It is easy to recoat, but unless you are talking about small areas must be sprayed. (Hell, spray it anyway!)
There are some alternatives in the water based polyurethanes. Still little experience on that front here, but the upper end, high grade products such as ML Campbell, Sherwin Williams industrial line, Oxford, etc., make some great products that don't yellow.
Shellac as an undercoat is a great idea, especially if you are going with the big box store finishes like Minwax, Olympic (I wouldn't use their products) or Varathane.
I believe that the Sherwin Williams products request that you don't use a primer at all, but put a multiple coat application of their product instead. The theory there (well tested BTW) is that a clean finish in proper application sticks to itself better than it would another product.
If you cannot find the products you want locally, I would go to your city's biggest Sherwin Williams store. They have so many damn products I am sure they must have a water based clear finish that is UV resistant.
I am just now digging into the Sherwin Williams line. With the demise of my favorite commercial coating supplier here in town, I have been looking for a new finishing line to use. SW has some fantastic products. Pricey, but with a professional discount not bad.
As an aside of my personal opinion, I don't really care what I spend for clear finishes. An ugly looking job is its own punishment. As you go up the ladder on product quality you will find that many of the better quality products not only are much more forgiving in their application, they give a better end product.
Often times you are talking about just a few dollars difference a gallon to get from OK quality to great. If you have problems with a product and you get an unacceptable job at the end of its application, a few bucks at that point seems pretty inexpensive. A trip to a real paint/coatings store can be well worth the trip to see what is out there.
As far as the water based stuff goes, you might want to ping BARRY. He finishes kitchen cabs and the like, and he could tell you about the issues with MLC products and water exposure. I think he would know if there was a UV inhibitor for you application.
Robert
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I agree with most of what has been said EXCEPT the part about Sherwin Williams. I have used their Nitrocellulose Lacquer in the past. It is the best! However, I have been trying to use their water based lacquer off and on for about 2 years now. I am not a happy camper. It is a real challenge to get a consistent coating. Maybe I don't have the correct HVLP system,but I don't recommend it for amateurs!
I just switched back to my old favorite Hydrocote. I have used their water based Super Lac and their Polyurethane in the past with great and EASY success. Even old stuff product works great and goes on easily. I am just about to try their Resistane replacement for Super Lac this weekend.
Len to finish up a job. success.
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Most of the replies seem, to me, to suggest repair of exterior casings. Condensation on the windows and subsequent damage, to me, implies interior casings. I'm supposing the poster is citing moisture damage, not weather or sun damage.
Use a marine finish, if you are repairing the interior. Maybe even apply tung oil or BLO, then topcoat after it dries very well. UV light shouldn't affect the finish (through the window panes), too much, except after several years, maybe.
Double posted?? Sorry if I did. I got an error message when I "sent" before.
Sonny
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Yes, I wasn't clear. I was referring to the interior casing around the windows. The casings themselves don't get condensation, of course.
The windows, even though they're good quality low-e windows, still get some condensation after a shower, especially when it is brutally cold as it is right now.

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snipped-for-privacy@uiuc.edu wrote:

I like ML Campbell Ultrastar.
BTW... EVERYBODY makes a great nitrocellulose lacquer...
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Perry Aynum wrote:

It would seem to me the first step would be to repair the cause of the cold air infiltration which is causing the condensation.
--
Jack Novak
Buffalo, NY - USA
  Click to see the full signature.
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Oak (and maple, and some other woods) mildew badly when wet (making dark stains, aka "spalting"). Shellac can turn milky with moisture absorbed.
Substitute other materials, it'll work better. How about spar varnish on yellow cedar?
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