Cleaning a Stone

 If by double sided you mean two sides looking different, I don't know how you would tell the actual grit count beyond visually assessing coarse or fine unless it is printed on the stone. As to cleaning you really don't give enough info, IMO.  What do you mean by "filthy"?  Has the stone been used with oil or water?  If oil, I imagine a drop or two of water will bead up.  If water, then a couple drops of water will probably quickly soak in.  If it were me, I'd determine if oil or water was the medium and proceed to flatten the stone.  Using a pencil inscribe a moderate grid on the side to be flattened.  Then use either a flattening stone or else some 320-400 grit wet sandpaper that has been wetted and placed on a nice really flat surface such as a hunk of polished marble.  You can usually get a piece of marble tile from Home Depot for a few bucks.  Wetting the paper and the surface keeps the sandpaper from moving around, kind of like the wet paper towel between your countertop and a plastic cutting board.

Applying even but light pressure make either small circles or figure 8's with the stone on the surface.  Check the pencil marks frequently until they have all just dissapeared.  You may even want to put fresh pencil lines on and repeat the process.  If the stone is now flat the new pencil lines will quickly and evenly disappear.  This won't clean the stone, per se, but you are removing an outer layer.  If it is still discolored it will be more of a cosmetic problem that will perhaps improve with a bit of scrubbing with a bristle brush.

The above applies to stones that have been used with water.  If the stone's history is oil, I would proceed the same except instead of sandpaper I would use something like the DMT brand of diamond hones, say the 325 grit.  They can be used dry because you don't want to mix oil and water.  If you say stored in a shed, and filthy, I suspect it was used with oil and used to sharpen shop tools.

Hope this helps,
Rich

Edit:  I say the diamond stone can be used dry but upon reflection I would recommend lubing with oil if the stone is impregnated with oil.  The diamond stone is actually not stone but steel and the oil would clean up easily.  For actual sharpening the diamond stones are used dry.
Edited by CaboSailor - 3/19/10 at 1:58pm

Not a "wet stone," but a "whet stone."  To whet is to sharpen -- as in "whetting" ones appetite with an appetizer. 

A stone with "two-sides" is called a "combination stone."  Each side is a different grit -- one significantly coarser than the other.  What the actual grits are, depends on the particular stone.  There are three basic processes to sharpening -- profile/repair, sharpening itself, and polishing.  Two surfaces can't do all three, so it helps to know the grit levels before jumping into any particular task. 

Cabo has a lot of things right.  One of them is that the first thing you have to do is determine whether the stone is a "waterstone," or an "oilstone."  That's fairly easy to do, despite the fact that not all oilstones have ever been used with oil.  Of course, most of them have been used with oil.  The vast majority of whetstones to found in America are oilstones, not waterstones.  So, you really shouldn't be too surprised if oil was used.

Soak the stone in water deep enough to cover it completely for about ten minutes, then start scrubbing it with a stiff brush.  No soap, no detergent -- just the brush.  If it's a waterstone, most of the dirt (actually "swarf") should start coming off.  If it's an oilstone -- especially if it's been used with oil -- the brush won't make much of a dent in the grime.

Don't worry about getting water on an oilstone.  Cabo was mistaken about that.  It's absolutely not a problem.  On the other hand oil on a waterstone can be quite a problem -- and you really shouldn't get soap on a waterstone either.

If it's a waterstone, there's not much need to clean it further.  Normal flattening and use will keep it clean enough.  The grime is a mix of dried out abrasive, binder and swarf called "slurry," aka "mud."  Most waterstones work best with a bit of left over slurry.  And once you do flatten and clean them, you have to work up some mud by sharpening or with a nagura stone to make waterstones work well.

If, as seems more likely, it's an oilstone, and it's as dirty as you described it's also probably clogged.  Clogging means that the stones pores are full of swarf and gunk and that the stone can no longer cut metal cleanly.  In turn, that means that stone will have to be thoroughly cleaned.   

There are a number of ways to go about it, depending on how dirty the stone is.  If the stone is really filthy, you'll have to soak it in a solvent like kerosene or mineral spirits, and do some sanding (you can use ordinary coarse sandpaper).  However, as a preliminary let's start with something easier. 

Try scurbbing the stone with an ordinary scouring powder like Comet or Ajax and a stiff brush.  A wire brush like a barbecue brush is fine.  Take your time and repeat the process a few times.  After a while you should at least be able to see the actual colors of the stone.  

If one side is orange-red, and the other grey-brown you have a Norton combination India -- and that's a good thing.  The dark side is a coarse India and is useful for repairing knicks.  The orange-red side is a fine India and is a very good stone for working up a sharp but coarse edge on soft steels.  An 8 x 2 x 1 coarse/fine India runs just under $20. 

If one side is light grey and the other is dark grey, it's probably a coarse/fine silicon carbide stone from one manufacturer or another (possibly a Norton Crystolon), and is most likely not worth saving.  Not that the stones aren't useful, but they're not a first choice for kitchen knives (too coarse), and they're very cheap to replace.  Nortons cost around $15, and everything else is cheaper.

If either of the surfaces is white or pinkish-white, chances are you have a combination Arkansas.  Combination stones aren't expensive, but even combi Arkansas are still probably keepers.

After scrubbing and scouring the stone, the next step is to thoroughly wash it.  The easiest way to do that is to run it in the dishwasher a few times.  You CAN do this with dishes in the dishwasher -- no problem.  But if you do, it's probably best to give it it's first ride when no woman is present in the house. 

Another way, is to get some cheap chain and put it the bottom of a non-reactive pot to allow water to circulate beneath the stone, add some water, some dishwasher detergent (you want the dry stuff), the stone, and boil it for ten minutes.  Turn the stone over and boil it for another time.  The diswasher doesn't do quite as good a job, but it's easier.

If that doesn't get the stone really clean, you'll have to soak it in kerosene or some other solvent for a few days to loosen the dried up oil that's clogged the pores, thoroughly wash it (dishwasher), and sand it off.  You can use regular 120# sandpaper if you like.

For the time being, there's no need to buy a $50 DMT to take care of what might be a $5 oilstone. 

Anyway, get back to us and let us know whether it's a water or oilstone, and what the colors are.  Once we have some idea of what the stone looks like, we can probably identify it and give you some idea of what it should be used for, and whether it's worth spending a lot of time on or whether, if it's cheap enough, it would make more sense to replace it. If you have a digital camera, pictures would make it easier.

Hope this helps,
BDL

PS.  If you want to get into the differences between oil and waterstones, ask.

If you're right about the age, it's almost certainly an Arkansas.  Sixty years is a little old for an SiC, and a nice wooden box a little rich for any manmade stone.  The light grey side was probably originally white and was probably either a Washita or soft Arkansas.  The dark side is probably a "surgical black" Arkansas.  As a practical matter you can't get good Washitas anymore and good surgical blacks are pretty scarce as well (although you can still get reliably good blacks from one source, Hall's Pro Edge).

Whether it's worth cleaning up enough to make it work as well as ever it could is an open question.  It depends on you, your knife kit, and what you want from a sharpening kit.  

Modern waterstones are faster and more efficient than any Arkansas, and with the right grit choice you can get an even finer finish than you could with any Ark -- not to mention a heck of a lot faster. 

So, what are you planning on shapening?  If kitchen knives, you probably don't want to sharpen modern Japanese knives with them -- but they'll handle just about anything else, slowly.

BTW, the whole thing about "slow" and "fast" isn't just how long it takes.  Slower stones take more strokes, and more strokes means a higher probability of error (dulling instead of sharpening). 

I'm not sure how much this will help, but you may want to take a look.

BDL

Not to hijack or anything but now you've have me curious.

  I have a combination stone which is orange-red on the one side which is actually the coarser grit and a slate grey on the other.  It measures about 7" x 2" x 1" so would this be an india combi stone?

 It's about eighty years old now and has always made me wonder about it. 

Orange is almost always Norton India.  Brownish orange is a medium India, and reddish orange is a fine India.  I'm not aware of any combis sith a medium India.  Norton's made the IB-8 (8x2x1), coarse/fine India forever.  Norton also made two India/Arks.  One a fine/translucent I don't think they make anymore, and the other a medium/soft they still do.  But I'm not sure how long ago they started making India/Ark combis. 

Get the stone super clean, try sharpening and polishing an appropriate knife or tool, and let us know how it works out.  A translucent Arkansas is will be very slow, but should take you to a very fine polish.  Translucent Arks were one of the two standard final stones for dental and surgical stones, so that should give you some idea of what they can accomplish with reasonably good technique.  

A fine India cuts quickly and should net you a very good working edge.  If you thumb drag a fine India edge it should feel sharp but a little rough.  A medium isn't a lot faster but is a lot coarser.  It's not really about sharpening, but more about profiling. 

On the other hand, with good technique a soft Arkansas should get you pretty close to what you expect from a good knife out of the box.  That is sharp, but not highly polished.

There are plenty of soft Arks around, and they're fairly inexpensive.  So if your stone is the medium/soft it's easy to replace -- about $45 for the stone, and $60 for the stone plus a (very good) "sharpening station" and a couple of accessories.  But if one side is a translucent from sixty ears ago it's a find.  It seems like most modern mines are a little depleted but the stones they do produce are good quality.  It's still pretty easy to buy a high quality translucent, but expensive.  

Hope this helps,
BDL