[Alexdi]

I hope someone can point me in the right direction before I dig myself into a deeper hole. I have an apartment with unfinished gray/white stone tiles with a rough surface. Last year, I (stupidly and ambitiously) decided to coat the floor with something to make it easier to clean. That something was this:

http://www.minwax.com/products/oil_based_clear_protective_finishes/fast_drying_polyurethane.html

It said it was clear and suitable for floors, so that's what I thought I needed. It turned out to be tinted yellow, which I discovered only after doing half of my floor. So now half the floor is a matte grayish white, and the other half is a dingy and shiny yellow.

Having clearly chosen the wrong product and soon to move out of the apartment, I decided to strip off the poly. Much deliberation and questioning of staff at Home Depot resulted in me buying this:

http://www.wmbarr.com/product.aspx?catid=36&prodid=63

I tried a tiny dab in a corner and it stripped the poly off very quickly, so I tried it on a full tile. I left it for an hour and was pleased to discover it stripped off the poly. But... it also turned the tile noticeably pink. So now my (landlord's) kitchen floor is a patchwork of ugly colors.

What stripper can I use to get off the rest of the poly off without dying the tile below? I assume it'd have to be clear, but really, beyond that I have no idea. If this item can be purchased at Ace or Lowe's or Home Depot, that'd be awesome.

And a bonus question, is there anything I can put on the pink tile to make it whitish again? Soapy water didn't do anything, nor paint thinner.

Thanks for your help, my damage deposit appreciates this quite a lot!

EDIT: Here's a picture that should give some idea what was there before, what I did, and the result of using the wrong stripper.

 

[Alexdi]

So, I solved this one. The Citristrip needed mineral oil or KS3 (Klean Strip 3) "after wash" to take away some of the pink appearance. That one tile is not completely perfect, but in the dim lighting of my kitchen, the color difference isn't apparent unless you're looking for it.

As to the rest of the poly, I used KS3 clear liquid stripper. My procedure was as follows:
1) Pour a puddle of KS3 over 1/4 of the area of a particular tile
2) Use a 2" brush to spread it evenly across the entire tile
3) Wait a minute (or just start pouring on another tile and come back to the first when you finish), then use a plastic paint scraper to take off the poly
4) Do a few more tiles, then come back to the first with a handheld plastic scrub brush after the surface has dried to get all the uneven areas the scraper couldn't pick up

KS3 is extremely effective. The poly would come off on the brush literally as I was spreading the KS3 over the tile, not 5 seconds after I'd poured it. Citristrip may have been even more effective, but I wouldn't use it on anything porous.

Some notes:
- Err on the side of more stripper. Not enough results in having to do the tile twice and having streaks of leftover poly.
- I started with a steel scrub brush, which ended up leaving a gray residue I had to mop the floor to remove. Steel isn't necessary, the poly in the crevices should come up easily with the plastic brush after it dries. If it doesn't, use more stripper.
- Don't accidentally mix 409 and mineral oil by dumping them on the floor, they'll react and make a nasty smell.