Sharpening in Japan developed into an art form during the evolution of the Japanese sword, the Togishi (sword polisher) used a variety of different grades of natural stone to shape and refine the forged blade, the many intricate stages of polishing refine the profile and appearance of the sword, revealing it’s astounding beauty and unlocking the breath-taking sharpness that the edge is capable of.
Sharpening with Japanese waterstones is regarded as one of the most effective methods to maintain knives and tools. Here is a basic overview to the different types available:
(Rough stone: used for bevel setting, thinning and repair work)
(Medium grit stone: used for refining the edge and removing scratches from the Aratoishi)
(Fine stone: Polishes, refines and de-burrs the edge)
The cutting edge
The edge of your knife under magnification will have what appears to be thousands of microscopic teeth, the size and uniformity of these teeth are dictated by the abrasive used to sharpen the knife. Rough stones leave very toothy edges that make the knife cut best when pulled back and forth; Japanese knives are designed to be used with a push cut, to enable this a finer edge is recommended.
Polished vs toothy edges
The types of food your cutting should influence your decision as to which stone to finish the sharpening with. When cutting delicate ingredients like fish or herbs for example, a super fine edge is recommended as it will very cleanly cut these delicate ingredients. A knife used for general Mise on place will benefit from a toothier edge, this will better engage with a larger variety of ingredients and be a little more robust.
Manmade sharpening stones have controlled particle sizes, making them highly efficient at cutting the steels in which they were intended for.
Consisting of abrasive particles held within a resin bond, generally vitrified stones need soaking to allow the stones to effectively release abrasive during sharpening.
The bond of a ceramic stone is made from magnesia, this gives the stone greater density and a higher cutting efficiency. Heavily alloyed stainless knives and powdered steel cutlery are much more effectively sharpened using this type of stone.
These rough stones are used for levelling out the surface of your other sharpening stones. Stones that become dished won’t be as effective so regular flattening is recommended.
Nagura stones are used for conditioning the surface of your sharpening stones after flattening, for unclogging steel from the pores of your stone during sharpening or for raising an abrasive slurry. Natural nagura stones are also available.
Tennen toishi (Natural stones)
Natural sharpening stones vary enormously in price, appearance, hardness and cutting ability. These Stones are best utilised on carbon steel cutlery, allowing the sharpener to bring out the contrasting steels used in a blade or bring out a temper line that may be present. The natural abrasive particles released from a natural stone fracture during sharpening, thus the slurry formed on the surface of the stone will become more and more refined giving you a finer finish that has different sized teeth forming the edge; a natural stone is capable of leaving the edge of a knife highly polished and at the same time toothy. Natural stones are much more expensive to buy and take a greater understanding to use to their full potential.
Diamond plates are extremely aggressive and remove material rapidly whilst remaining flat. They are extremely useful when used for flattening other sharpening stones; caution is recommended when using diamond plates for sharpening.
Honing steels/pull though sharpeners
Honing steels often create recurve at the heel portion of a knife when used frequently, when this happens the edge wont fully contact the cutting board rendering that part of the knife ineffective. Diamond steels in particular can rapidly disturb the profile of a blade and should ideally be avoided.
Pull though systems cannot account for blade thickness, hardness, steel type and the type of ingredients you’re going to prepare. It’s impossible to realise the full potential of your knives with these systems.