Honing & Sharpening your Japanese style kitchen knife

Much has been said and written about sharpening and polishing of Japanese blades. This essay is an attempt to simplify (hopefully not over simplify) and inform the novice about the nature of sharpening and polishing his or her knives.  It is important to note that by far, no amount of written text can teach you how to sharpen and polish. In order to learn - you must practice this art  "hands on".  The best way to go about it is to get a very cheap knife and some cheap stones and learn how to sharpen - then move on to more exotic blades and stones.

A word or two about stones:

 Your knife should never be sharpened or polished on anything besides a water stone. Oil stones and steels will ruin your cutting edge. A professional will use several kinds of stone grades to sharpen a knife. The Arato - a coarse stone, The Nakato - A fine stone, and the Shiageto - an extra fine finishing stone.  There are several sub-divisions of stones for each type, as well as various kinds of stones within this sub-division. However, for a home cook a good Nakato stone will work just fine.

Natural water stones are found in various places in the world such as Japan, Belgium, Slovakia, Germany, USA, and even here in Israel. Natural Japanese water stones have been all but depleted and as such, their prices have a tendency to be very high.  As a result, they are mainly used for sharpening traditional Japanese swords and are not widely available. Instead, Synthetic water stones are commonly used to sharpen fine kitchen cutlery. Synthetic stones  are usually made from silicon carbide or alumina. there are many makers of synthetic water stones providing a huge range of grit sizes, anywhere from a coarse 80 grit to a super fine 30,000 grit. A newly purchased, non-sharpened knife will usually require some work with a coarse arato of about 80 to 220 grit. After the foundation work is done it's time to move on to a finer sharpening of the edge, and for this a Nakato of about 400 to 1500 grit can be used. From here on it's all about the finer finish. An extra fine Shiageto of 3000 grit and over will be the stone for the final finish.

The explanation above is a simplification of reality. In fact, in real life, sharpening and polishing is a very labor intensive process and requires a lot of skill and experience. The number of stones and grit sizes used are quite elaborate and  require many hours of work to achieve good results.

Water stones need regular maintenance just like the knives they sharpen. A stone will become uneven or "bowl out" after some use. It is imperative to flatten the surface of the stone prior to sharpening with it otherwise, undesired effects will ensue. To flatten a stone, a flattening stone is required.  These are special stones that are harder than the stone they flatten and can be purchased in most places where water stones can be had.

Some thoughts about sharpening:

The sharpening stone must be soaked in water, usually for about 30 minutes before use. Then, the stone is to be placed on a solid, non-slip surface and all through the sharpening it must be sprinkled with water. If a stone is allowed to dry during sharpening it will begin to sharpen unevenly, possibly scratch the surface of the blade in ways undesirable to the user, and potentially become damaged by a blade that may accidentally stick into it. Having said this, it is important to use a rational amount of water while wetting the stone, so as not to wash away the toguso (muddy slurry) that develops during the sharpening action, and acts as a sharpening agents as well as the stone itself.

The main difference between sharpening a Japanese and a European blade is the Kiriba (the path of the blade), the area that lies between the stone and the blade. In Japanese knives, this area is wider. While sharpening a Japanese style blade the Kiriba must remain uniform from tip to heel. The Shinogi (top of the bevel) will acts as a guide that shows what line to follow while sharpening.

In straight shinogi blades such as the Usuba the blade may move "up and down" in almost straight lines, while in curved shinogi blades such as the Deba or the Yanagiba the movement follows the shinogi line and thus is slightly curved. The blade should always conform to the shinogi line as it moves along the stone, or the angle of the bevel will change - this is sometimes irreversible. Following the line of the shinogi during sharpening takes practice and experience - but after a while, it becomes "second nature" to the sharpener and is very rarely a source of adversity during the sharpening process.

Once the kiriba is positioned correctly on the stone and is sharpened with the shinogi acting as a guide you should expect a burr (kaeri) to develop and curl towards the Ura - The "back" of the blade. A telltale sign of the development of the Kaeri  is the appearance of a bright white line along the edge, as light is reflected from it. The Kaeri can also be felt with the cushion of one's finger (use caution when handling a cutting edge). So, in essence it could be said that the process of sharpening a Japanese blade is the repeated formation and removal of the Kaeri. The Kaeri  can be removed by reversing the blade and gently whisking it across the stone on it's Ura. Some professional prefer the traditional method of running the blade gently through cherry wood or cork. No matter how you decide to de-burr your blade, keep in mind that you are really trying to get rid of the burr - not the edge. If, instead of removing the burr you are in fact continuing the grinding action of the blade it is counterproductive because you are changing the angle and this will in most cases make the knife dull and you will have to start over again. Your cutting edge is jagged. No matter how fine this jaggedness is - it is there.

Sometimes, the jaggedness is not visible to the naked eye - but if you look at the cutting edge under a microscope, you will see what appears to be little teeth, like a saw blade. These "teeth" are what makes cutting possible, and is what gives the cutting edge it's ability to "scream" through anything that stands in it's way. The finer the stone, the finer the serration. However, no matter how fine a stone you use - you will always have microserration on the cutting edge. This is a desired trait, but it also holds a weakness. These micro serrations are where the blade will sometimes chip. In order to make the cutting edge slightly more durable (for example, in Deba knives that are used to chop through bones) a secondary bevel, or a "double edge" called a Koba is created. The Koba does not affect the sharpness of the edge - it only makes it a bit more durable for those extra rough tasks. The Koba is achieved by changing the angle of the Kiriba relative to the stone during the finish stage.

Note:  Most of the knives we make have a perfectly FLAT back. Please let us know in advance if you wish for a hollow ground back.