I own a "medium" grade ceramic stone by Spyderco which works excellently without any cutting fluid (typically used dry). These ceramics are manufactured using synthetic sapphires which are just one notch below diamonds on the Mohs mineral hardness scale. The Mohs Scale was developed by Friedrich Mohs in 1812 and is used to classify minerals by hardness. It is a relative scale, being that each mineral is classified based on its comparison to another mineral of known hardness. A sample of the scale is shown below:
DMT diamond bench stone which flattened it well, but really did a number on the steel plate. I have read in other blogs and message boards and a common theme seems to be that the harder Spyderco stones (fine and ultra fine) come very flat but I can not speak from any personal experience on the matter. The Woodcraft website states that the manufacturer guarantees the stone's flatness within 0.020 inches or roughly one half of one millimeter. These stones can be cleaned with a powdered kitchen abrasive cleaner like "Barkeepers Friend", soap and water or put in an autoclave (if you just so happen to own an autoclave).
The Shapton ceramic on glass stones are a newer concept, but one that I would love to try out. They come very highly recommended from many sources. They can be cleaned with a little water or a small amount of soap, they also require a little water on the surface before and during their use but they should be stored dry. From what I have heard and read they do come very flat out of the box, but they also require flattening prior to each use just like a regular waterstone. Shapton recommends using their DGLP (Diamond on Glass Lapping Plate) to flatten the stones. The lapping plate is rather expensive ($380), as are many of the ceramic on glass stones (especially the higher grit stones) but they are of high quality and should last through many years of regular use.
I just got a set of Spyderco ceramic files, which are spectacular. They come in a set of various shapes which is helpful for sharpening a variety of tools and shaping all kinds of small metal parts, they are all approximately a 1/4" diameter and 5" long. Because they are so hard, they will sharpen and shape anything including carbide blades, just like the full size ceramic stones. I have tried them on several different types of metal already and they work like a charm . They clean up with a little soap and water or Barkeeper's Friend. I haven't tried the triangular one on a saw yet but I am curious about its ability to sharpen one. Another nice feature about these is that they come in a leather case which is actually really well made. The case keeps them from rattling around in a tool chest and prevents them from getting damaged.
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