Several years ago I decided to lap my well used Arkansas stones -- Washita 
(pink/grey), Soft Arkansas (grey), and Hard Arkansas (white).  I used a 
piece of window glass sitting on newspaper on top of my cast iron table saw 
surface, which I know to be very flat.  I made a slurry with silicon carbide 
powder and water.  You can buy silicon carbide powder at a lapidary supply 
shop and it comes in various grits to be used for tumbling agate and the 
like -- I bought coarse (60 to 80 grit) and medium (220 grit).  Using a 
figure 8 motion, I lapped each with the coarse powder.  Because the stones 
had been used with oil, they didn't absorb the water and it was easy to see 
the dished portion.

When the stones were flat, I turned the glass over and repeated the process 
with the medium grit silicon carbide powder.  This left a nice flat surface 
which I gave a final dressing with a sheet of 320 grit "wet and dry" 
sandpaper and water. My stones were not badly dished to start with, but if 
they had been, I would have flattened them on a cement block before using 
the silicon carbide powder.  It took around 2 hours to lap the three stones 
on both sides.

Ken Vaughn 

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