"You may be able to sand down to unstained wood and re-seal." The problem that usually shows up is that the urine can penetrate at the joints between the strips of floor, and you simply cannot 'sand out' enough to remove the staining that came in from the edge of the strips. If it is a small area you can remove strips and replace them. If the floor is old look at closets fr a ready source of matching wood. The new wood in the closet will not show as badly

I had my floors all totally refinished (they were awful) about 10 years ago, - before all other refurbishments were done, which sometimes abused the floor finish (I'm sure my dog helped some :). The poly is mostly worn off and I'm now about to screen them before putting a few new coats on, re-crowning the totally finished place! In two spots there appears to be an oily-like substance - or stain - that got under or into what finish is/not left. I've tried regular cleaning methods with no change. How can I be sure these are 'cleaned up/out' after screening (I'm not sure if I'll be able to tell after screening) or perhaps there is something else I should have available or plan to do...? (If this was a piece of furniture with 'maybe a food stain, I might use a dark stain to try to blend all better, but I want to keep all of these floors the natural golden color with just poly.) Thank you for any help, info/advice! D.

I am thinking I was talking about benches that I did completly out of the sun in the shop, for some reason those kind of project have to be set outside for the twp finish to set up. Unless your porch is completly walled/roofed in making it dark inside twp will be fine. J

You want to start with a chemical stripper. Methylene Chloride is the most common, fastest working, strongest, and unfortunately, most noxious. Put it on and let it work. Do a few steps at a time. If you have nice weather, open the windows for a breeze. The biggest problem people have is not giving it enough time and then having to spend more time and effort on a second, third, fourth ... application. Scrape off with a putty knife and follow up with a scotch-brite stripping pad. Neutralize / rinse as directed on the can of stripper. Then let the wood dry thoroughly. This will remove the polyurethane and generally most of the stain. Oak, having coarse pores in the spring-wood, might retain some of the stain in these rings. Don't kill yourself trying to get it out, just leave it as a contrast. Often people think they can just "sand off" the finish and avoid the chemicals. Bad idea. After a whole weekend and a pile of gummed up sandpaper, and only part way through the project, they think it's a bad idea, too. The other risks are that the finish is removed unevenly (causing the subsequent stain to absorb unevenly) and if there is veneer (not likely on your steps, but highly likely on casegoods), it's easy to sand through. An exception to this guideline is if you are doing a hardwood floor with a drum sander and removing significant amounts of wood with 36 grit belts. Once dry, do a light sanding with a fine sandpaper (120-220). I think you might want a stain, something like a "golden oak" if for no other reason than to even out the tones in the various pieces of wood. If you want to preview what the unstained wood with varnish only would look like, simply wipe some areas with a rag dampened with mineral spirits. I would also recommend applying a good floor-quality polyurethane. This is one instance where you need the abrasion resistance of a poly. Get a good brand, not just a can of polyurethane at the grocery store. Just because it says "Great for Floors" on the front of the cans mean that it's the best choice. If you want, you can thin it 50-50 with mineral spirits, creating your own "wiping varnish" and wipe it on. You will need 2-3 times as many coats as a brushed on finish, but it's fairly foolproof as a DIY or beginner. I also like to sand between coats to smooth it all out, remove imperfections and dust nibs. If you are wiping on, every other coat should be OK. If you are brushing, be sure to thin it so it flows out better.