Whetstones may be natural or artificial stones. Artificial stones usually come in the form of a bonded abrasive composed of a ceramic such as silicon carbide (carborundum) or of aluminium oxide (corundum). Bonded abrasives provide a faster cutting action than natural stones. They are commonly available as a double-sided block with a coarse grit on one side and a fine grit on the other enabling one stone to satisfy the basic requirements of sharpening. Some shapes are designed for specific purposes such as sharpening scythes, drills or serrations.[9] 

Different knives are sharpened differently according to grind (edge geometry) and application. For example, surgical scalpels are extremely sharp but fragile, and are generally disposed of, rather than sharpened, after use. Straight razors used for shaving must cut with minimal pressure, and thus must be very sharp with a small angle and often a hollow grind. Typically these are stropped daily or more often. Kitchen knives are less sharp, and generally cut by slicing rather than just pressing, and are steeled daily. At the other extreme, an axe for chopping wood will be less sharp still, and is primarily used to split wood by chopping, not by slicing, and may be reground but will not be sharpened daily. In general, but not always, the harder the material to be cut, the higher (duller) the angle of the edge.

A common myth is that sharpening steels actually sharpen knives, and can replace stones or other sharpening devices. Steels actually hone a knife and help keep its edge if used regularly. A steel should be used before and after each knife use for proper maintenance. Easily enough, it's used the same way you use a sharpening stone. To find the proper angle, hold the knife horizontally with the edge touching the steel. Move the spine upward to create a 45-degree angle, and then half that again for your optimal sharpening angle.
On the other hand, the surfaces of knives that have been looked after may blacken a little, but this is a different type of iron oxide than ordinary reddish rust. This black oxidation is mainly triiron tetraoxide (Fe3O4). It coats the surface of the metal and prevents ordinary rust from getting in. It will not discolor food and poses no threat to hygiene.
Whetstones may be natural or artificial stones. Artificial stones usually come in the form of a bonded abrasive composed of a ceramic such as silicon carbide (carborundum) or of aluminium oxide (corundum). Bonded abrasives provide a faster cutting action than natural stones. They are commonly available as a double-sided block with a coarse grit on one side and a fine grit on the other enabling one stone to satisfy the basic requirements of sharpening. Some shapes are designed for specific purposes such as sharpening scythes, drills or serrations.[9]
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