Poly over old stained wainscoating?


We have some old dark staind wainscoating in one of our bathrooms. I would like to clean it up and put on a protective coat of poly.
I'm not sure what the old finish is, but I was thinking of doing the following: 1. Cleaning it with alcahol or mineral spirits? (I know if the old finish was shellac, then alcahol would tend to dissolve it) 2. Cover it with a couple of applications of oil-based wipe-on satin polyurethane
Is this a good idea? If so, anything to add to my approach? If not, any suggestions on a better approach?
If possible, I would like to avoid a major project of stripping off the old finish and staining and starting from scratch...
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How big is this bathroom? If you are trying to improve the looks, then there really is no substitute for doing it right. Might be even easier and faster to simply replace the wainscoting with new.
What you are presently proposing could end up with something worse than what you have now.
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snipped-for-privacy@dog.com writes:

I would prefer not to replace the wainscoting for 2 reasons: 1. I assume that the quality of old wood is almost always better than new 2. Ultimately, we are likely to remodel the entire bathroom, so I would prefer not to invest in new materials that may be ripped out in 5 years.

Other than ripping out and replacing, how would you go about it... (and can it be done without stripping off all the old finish and stain)
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In that case, clean with TSP, lightly sand, and paint it.
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blueman wrote:

try rec.woodworking
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wrote:

WOW!! Great idea!
Wait a minute.....
Robert?
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The finish on the wainscot is probably shot. It most likely has little bits of soap here and there, hairspray, a splash of this and that, and no telling how much cleaner has been used on it.
You didn't say what the pattern was on the wainscot, but I will assume that it is at least wood since it was stained.
If it is a good factory finish, your coating will flake off after a period of use, depending on how long, hot and steamy the showers are after finishing.
You didn't say how old the finish was, either.
If it is a shellac based finish in a smaller bathroom, you will almost always be able to tell the degredation of the finish as you get closer to the shower. Shellac in the bathroom: bad.
If there is no or little degredation of the finish and it looks very smooth and uniform when viewed at an obtuse angle in the light (flashlight), it is probably factory finished. Look for telltale signs of hand finishing behind toilets, in corners, behind doors in tight spots, etc. If it is all *perfect*, then it will be a factory cured finish made to repel things that want to stick to it.
When folks were still remodeling bathrooms (boy.... that seems like a long time ago!) we ran into the prefinished panels from the 70s and 80s when dark colors were the rage. I found no way to refinish them satisfactorily, so if the client insisted, we replaced them with other panels.
If it was a bead board pattern, we hooked up a ROS to the shop vac and sanded anything that was to be painted down to bare wood. The grooves in trims and panels were sanded as good as reasonably possible by hand.
As a sidebar, in the old pine bead board patterns, it wasn't unusual for the beads and grooves to be rough from the mill. Not so much of a big deal when you are staining or clear coating. When painting... it looks ugly. So the solution there is to sand the beads, and fill the length of the grooves with a tiny bead of caulk. Each one. Makes it look brand new.
After surface prep, we put on two/three coats of BIN (primer/stain kill) depending on how dark the stain actually was when we got to it. Then two coats of a good oil based enamel. Change out the cap rail, and you are in business.
When I look at anything that is stained dark, I don't give any options. Most of the time the question is "can you take off part of the color? We like it overall, but it is about two shades too dark".
The answer? No.
You can strip, sand, and restain, but that is exactly what you are trying to avoid.
I would replace it or paint it. There is no simple solution to a clear coat refinish job other than to leave it alone.
My 0.02.
Robert
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I bet it will work.
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blueman wrote:

If the old finish was shellac, you probably would have had water spots (white) on it by now. I would clean it first with cool water and detergent - I do the same with good furniture - which will not harm the wood if you don't saturate it and leave it wet. Bathrooms don't get greasy like a kitchen, so I would not be inclined to use m.s. I do use m.s. to remove wax and greasy dirt. Let it dry well. If the finish is glossy, rub it down with fine steel wool prior to clear coat. Vacuum dust very well.
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I assume m.s = mineral spirits. I agree about the lack of grease but was thinking that there must be 50+ years of grime there.
What would be the disadvantage of using mineral spirits? Also what about TSP, would that be helpful or necessary?
Finally, if surface is cleaned and the gloss (if any) is knocked down, can I assume that a standard poly would stick well and not start flaking off (assuming I apply it properly)
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Don't sell the grime short on screwing up your finish. If it has been cleaned with soap, there is left over oils and other remnants from different types of cleaners that remain after cleaning. What do you think provides the glue that forms dust and dirt into grime? If the remnants weren't left behind, the grime would simply be dust.

Sounds like you are willing to take a chance. Unlike a homeowner that will hopefully be garnering the praise of a wife for a good effort, I have to provide a warranty for my work.
Since a job done halfway is often its own punishment, I don't take chances with the extra effort it takes to do the job right.
However, you will be much less hard on your results than you would if you paid someone to do the job for you.
You shouldn't assume that because a surface is clean that you will get a good bond for a dissimilar finish that will sitting on top of an improperly prepared surface.
BUT, if you just want a quick job use whatever you have on hand to clean it, scuff up the surface and slather on the poly. Even in a steamy, wet environment you may get some good service time out of it.
Since you don't have a warranty to worry about, your options are pretty open.
Robert
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blueman wrote:

Yes, mineral spirits. Grime should come off with good scrub with household cleaner, just taking care not to let water puddle into joints or moldings. Wring out rag and scrub well. I do the same with good furniture that gets fingerprints, like the backs of dining chairs and have never had negative effects.

I haven't used TSP in many, many years. Don't know of disadvantages of m.s. other than fumes and disposal. I use a lot of it when stripping wood. Also used it to get old, gummy grease off kitchen cabinets, in which case the grease can soften varnish and you lose some finish along with the dirt. I have used m.s. also to take of built-up furniture wax - it is the solvent in paste wax.

Certainly seems so. Only thing I know that would allow flaking would be wet surface, high gloss or greasy dirt. Fine steel wool is good for taking down gloss, IMO, because it dulls finish more gently than sand paper. Gotta be sure to clean up fine particles of steel wool, esp. with water-based final coat because it can rust. Green 3M pads work well, too.
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blueman wrote:

Try a bit on a spot that doesn't show. See if it works. As others said, you want it really clean first.
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I ended up doing the following: 1. Cleaned the old beadboard with fantastic. 2. Rubbed with 0-4 steel wool and scraped away any (old) paint splatters 3. Filled holes with stained-to-match mix of West epoxy and low density filler 4. Wiped down with alcahol 5. Rubbed in some Minwax matching dark stain 6. Applied 4 coats of Minwax semi-gloss oil-based poly with a cloth
Looks great now -- only time will tell how long it holds up...
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