Removing polyurethane stains from grout

"That's not stain on your grout," announced the professional floor cleaner guy, crouching on the kitchen tile and picking at my grout lines with a razor blade. "That's polyurethane, circa 1980. Stuff looks like hell. Been stuck on that grout for 20 years. Paint stripper will do her though." Note: I had been thinking of my floor as male, but it was apparently female. That kind of mistake can cause trouble in bars, but I was in a whole other kind of trouble.

As I recently reported, all of my favourite household chemicals had failed to clean my weirdly dark grout, and I knew the previous owners had tried everything too, including calling in a cleaning service. But I was curious, so I called the local cleaning service too, and they went straight to work with their grout-bleaching chemicals. Nothing. No change. Then they tried their floor-stripping compound. Nope. Still grungy. We all sat on the floor for a while, staring at the grout lines, a whole lotta thinking going on.

The grout itself was buried under a thick yellowish-brown coating, like the nail polish you see on rebellious teenagers. That gave me an idea, so we tried nail polish remover. Suddenly there came a signal from the grout gods. The mottled veneer on the grout turned gummy. We scraped, reapplied nail polish remover, let it sit and then scraped again. After 15 minutes of drenching, dabbing, scraping, and inhaling acetone, the grout was finally bare and lovely. But, let's ask ourselves - is clean grout worth 15 minutes for every 12 inches in 300 linear feet of grout? Let's calculate: That's 4500 minutes, or 75 hours, or two 40-hour work weeks, not including lunch breaks.

I announced decisively that I didn't care anymore. But just then, the cleaner guy came up with a theory. He surmised that the obstinate coating was polyurethane, dating back to the nationwide polyurethane craze of the late 70's and '80's. He figured paint stripper was the only way to go. I squealed, as any concerned homeowner would, "Why the devil would anyone coat a slate floor with polyurethane?"

The floor guy couldn't tell me why. And that's when I knew I should have hired the psychic cleaners, the ones with the motto "We explain how and why the people who owned your place 30 years ago screwed up, so we can all blame those people while you pay us to fix it."

I did a bit of research. Twenty or thirty years ago, polyurethane was the modern wonder finish, all the rage as a replacement for wax, lacquer, varnish and shellac. Once they discovered how well polyurethane worked on furniture, people tried it on boats, metal, masonry, decks and tile, places polyurethane was never intended to go. It was a nasty era. Remember Phentex yarn? It was from the same period. I had a Phentex poncho. Remember ponchos? I'll stop now.

So anyway. Paint stripper did the trick in my situation. But while I was on the floor stripping the polyurethane with citrus-based paint remover, I received a stream of helpful communiqués from you, my fellow handypersons. Thank you. Here are some pithy excerpts:

Mag, Mag, Mag...where have you been girl? ZEP makes a fabulous grout cleaner - I know, I've used it on three bathrooms. Just pour it on, scrub with an old toothbrush (or your husband's if he won't help), rinse and voila!
Edna Mang, Bolton

Thanks, Edna. This is one of the products I tried first, before I realized my grout was covered with polyurethane. By the way, ZEP grout cleaner contains the solvent hydrochloric acid, so it works great on carpet saturated with cat vomit, even desiccated cat vomit in well-concealed locations which humans don't find for days).

Hi Mag,
I may have the answer for your dirty grout problem...and no muscle power required! A few years ago my dog was sick on my tile floor. I cleaned it with Fantastik and then left a little extra on overnight so it could soak into the grout. In the morning the spot was spotless. Last summer I cleaned my son's apartment's old, old bathroom floor the same way, but I had to do it 4 nights in a row. I have told sooooo many people about this so you may want to try it.
Doug and Dianne Lamb

Note: Thanks for the great tip, but your dog was only sick ONCE, a few YEARS ago? Cats are sick every twenty minutes.

I'm a mother of four and my mother lives with us too! My ceramic tiles take a lot of beating. I've used Old Dutch powder with a toothbrush sitting on a tiny footstool but that's a lot of work. But Oxy-Clean (for the laundry) is really fantastic - a little more expensive than bleach and Old Dutch powder but works well with a toothbrush and faster too! Apply the Oxy-Clean, rub into the grout with a wet toothbrush and leave it to soak for a few minutes, then scrub again with toothbrush and wipe with clean rag or sponge. Good Luck.
Carol Reis, Caledon East

Hi Mag,
Re: dirty grout. Try Mildew stain remover made by ZEP, purchased from Home Depot (32oz bottle ). Contains sodium hypochlorite. The stain remover dissolves most dirt as you watch, however a toothbrush works for more stubborn stains.
George, Pickering

Dear Mag:
Don't knock "the richly emotional foothills of peri-menopause"; they ensure that you will be believed when you threaten with death or dismemberment anyone who dirties your newly cleaned floor!
Carol Peck, Toronto

And finally, adventurous readers will be eager to try this ingenious use for a food product:

Hey Mag...why not try Tang on your floor. Since it works great on toilets, it may be your ticket to clean floors. My toilet was almost black from years of not being cleaned (before my time here) and from the minerally water we have. One pack of Tang and I could even see some white at the bottom of the bowl. Good luck.
Jen P.

Astronauts always pack extra Tang in case they pull toilet maintenance in Zero G.