whetstones? water, or oil-based

Hi,
I've been into woodworking for a while; just transitioning to marblecarving.
An instructor gave me what seems sound advice that to polish the marble, rather than chewing through sandpaper, to use a water-based whetstone to grind and polish it smooth. In this case, you want small, skinny fragments, not to pay for new, flat, large whetstones.
SO-- in my quest for trashed stones to pick up dirt-cheap, what's the difference between a stone that requires oil, and one that requires water? I assume the oil-based are tighter-bonded, and will dissolve rapidly with water...? Or maybe they'll still work for my purposes?
There is, that I know of:
carborundum (gray stones) aluminum oxide (white or maybe grey, the cheaper ones) silicon carbide (green usually, probably the binder holding the particles in place) diamond
...then a slew of natural stones, the minerals of which I don't have a clue.
which need oil as a rule, which water, what governs this? How to tell when staring at a photo on ebay of 25 trashed honing stones all jumbled together?
thanks! -Bernard Arnest
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Grit is grit, lube is lube. "Wet" stones are not as tightly bonded as oilstones, because their reason for existing is to rapidly create a slurry of their substance which does the polishing. Oil stones create a slurry slowly.
Polishing marble can be done with a chunk of limestone or other marble. Way it was done for years. Other good method is to use graded loose grit and a piece of wood. (Mandatory Woodworking Content) Might even consider a "scary slick" method using sandpaper.
Use what ever lube required to wash away the product of your efforts. If the stone was originally an oilstone, it'll be a bit slimy at first, but it'll come around.
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Not all water-lubricated stones work in this way. The friable stones, like the Japanese waterstones, use a slurry on the surface of the stone. Other stones aren't friable, work as a bonded stone, yet still use water as a lubricant. Most fine, hard stones (Arkansas are a good example) will work perfectly well with either water or a light oil (although not water after using oil!)
For use polishing marble I'd expect to use a hard-bonded stone. Using a friable stone for polishing a large surface rather than just an edge is a tricky skill -- it's one of the harder aspects to sword polishing. Try a cheap fine Japanese synthetic stone of maybe 4000 grit (equivalent) and upwards. These are hard enough to work without needing a slurry.
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wrote:

Of course he can clean the oil out with detergent, he just has to live with some slime initially.
I've always thought of the wet stone process more as lapping than honing, personally.
Once again, hair of the dog would be my recommendation.
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Unused oil stones can be used with water. If they've been used with oil, water won't sheet, so you're stuck with oil. Water stones are ruined the second some bonehead tries to hone with oil.
Any reason you can't wet sand with silicon carbide wet-dry paper? At Mohs 9 hardness, the paper won't wear as fast as it'll clog. Wet sanding with a few drops of dish soap added will keep the paper open and cutting forever.
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