Yup, old gunk of some sort that needs to be removed from the slate. Try getting it off by escalating through the various possibilities-- industrial strength wax stripper, ammonia, various organic solvents (with very good ventilation, denatured alcohol, acetone, Goof-Off etc) and then paint stripper starting with something like SafeStrip and moving to one with dichloromethane (again with very good ventilation) until you find something that takes it off. (I don't mean you should use all of them, just go from the gentlest to harshest until you find the one that is sufficient to the job). The good news is that its a rock and hard to hurt in any serious way. Once you get it to soften a scrub brush will get into the cracks. Wire brushes or abrasive pads can scratch the slate and should be avoided (white or gray Scotch-brite is OK, but doesn't do much. Red or green will probably scratch). Once it's clean apply a good quality sealer from a flooring supply place or as recommended by a stone yard-- it will look bad after it's been cleaned, but a coat of sealer will bring it back to like new.

Milo, I sent "just a pb" an idea on his "pretty pictures" thread, I love the geometric look. Try very large, 24" white travertine pavers with a cantilevered edge, larger if you have the budget. Cool enough to walk on (we're in Vegas), maybe do the edge as an ogee or waterfall look as well, for the pool coping. Heck, as long as I am spending your money, add some glass with a waterfall effect into the pool. I've seen one from the second story all the way to the waterline that spilled into the pool.The water trickles across the glass. If anyone can do it, looks like "just" can. Send pictures when you proceed, Barb

Rina, Bill and I had a delightful conversation last night involving you, or at least plants cuttings for you. Contact me privately for more information, as I think you'll be delighted, too. Bill's a generous guy, even offering to send me some jade cuttings, which I respectfully declined when I told him he's too generous and I didn't want to clutter up this Forum with questions about them. Talk with you soon!

Here is what a brand new sponge looked like after scrubbing one of the (same) tiles that are on the walls. Sorry it's out of focus. I'm sure I focused on the "no detail" sponge. Here is an old sponge and the same brand new one that I had just used on the wall. I used it on half of a 20" floor tile Here is my bathroom floor As you can see, I'm not rubbing on the top surface of the porcelain tile (unless the top surface is dirt!). While taking pictures for this thread, I did paid closer attention and looked harder at areas next to areas I'd scrubbed with the ME. I used the ME in a "X" pattern. I don't beleive anyone would ever notice it unless I pointed it out, but I finally DID see a slight color difference (lighter) in the area I cleaned. You have to stand back to see it. I'm guessing due to the color and pattern of the tile, this is (probably a perfect tile/color to hide filth!). I do use alcohol with my steam mop but not in the reservoir. I spray it on the floor as I'm cleaning. I thought steam as all I needed to clean and just sprayed on the alcohol as an added layer of germ eliminator. I have to respectfully disagree that MEs don't clean anything (unless "clean" isn't the same thing as "remove" in this case). It's removing grime that my steam cleaner can't. It's removed light scuff marks on my 7-8" baseboards. I was cleaning/removing some paint from the porcelain tile in the hall when I decided to LIGHTLY attempt cleaning/removing a scuff mark from the trim. I've been using MEs for years when I get a food splatter on my well sealed tumbled travertine kitchen backsplash. Just hit it once, twice at the most and it's GONE...even in a grout line. That's cleaning in my book :) I was looking at asking DH to touch up the baseboards all over the house before company arrives next month. They look great now. 90% of what I (cleaned?) shows no sign of removing any of the shine from the semi-gloss paint. I went a bit too hard on a couple of spots but unless you get the light JUST right and look at it at JUST the right angle, you can't see it. It has extended the need for touchup painting. I cleaned/removed light grime on doors and door trim being sure to use a very light touch. What didn't come off immediately will be touched up with paint. If I removed more gloss from the paint than I can see...that's OK (cause I can't see it and it looks better than dirt and scuffs). 99% came off lightly using the ME. This ALL started doing post remodel clean up and it just spread...