There are a couple of classes of traditional Japanese chef knife forging methods: Honyaki and Kasumi. The class is based on the method and material used in making the knife. Honyaki are true-forged knives, made only of one material: high-carbon steel. Kasumi are made from two materials, like samurai swords: high-carbon steel and iron forged together (known as san mai blades), with the steel forming the blade’s edge and the iron forming the blade’s body and spine. Honyaki and Kasumi knives can be made out of either of ao-ko or Shiro-ko steel. Based on their Kirenaga (duration of sharpness) and hardness, however they are more difficult to use and maintain. Additionally, there are high-grade, quality Kasumi knives called Hongasumi and layered-steel Kasumi called Damascus that have a longer Kirenaga.
Originally, all Japanese kitchen knives were made from the same carbon steel as Katana. More expensive san mai knives have a similar quality, containing an inner core of hard and brittle carbon steel, with a thick layer of soft and more ductile steel sandwiched around the core so that the hard steel is exposed only at the cutting edge. Nowadays, stainless steel is often used for Japanese kitchen knives, and san mai laminated blade construction is used in more expensive blades to add corrosion resistance while maintaining strength and quality.
Japanese Cutlery Production
Much high-quality Japanese cutlery originates from Sakai, the capital of samurai sword manufacturing since the 1300s. After the Meiji Restoration, the carrying of swords by the samurai class was banned as part of an attempt to modernize Japan. Though demand for military swords remained and many swordsmiths still produced traditional samurai swords as art, a large proportion of swordsmiths switched their focus to producing cutlery. The manufacture of steel knives in Sakai began in the 1500s, when tobacco was brought to Japan by foreign traders, and Sakai blade producers started to make knives for slicing up tobacco. The Sakai blade industry received a significant boost from the Tokugawa shogunate (1603-1868), which granted Sakai a special license and helped its reputation for quality (and according to some references secured them a monopoly). During the Edo era (1603-1867) (or specifically the Genroku time period (1688-1704)) the first Debabocho were produced, soon after followed by a wide variety of other styles. Making cooking knives and related cutlery products is still one of the biggest industries in Sakai, using a combination of modern techniques and old-fashioned hand tools to make stain-proof carbon steel cutlery.
Seki, in Gifu prefecture is today considered the headquarters of modern Japanese cutlery, where up to date manufacturing and technology has replaced ancient forging methods to produce a high-quality series of stainless and laminated steel cooking knives famous across the globe. The biggest cutlery-making firms are based in Seki, and they produce the best quality kitchen knives in the traditional Japanese style and the western style, like the Gyuto and the santoku.
Another famous center for traditional blacksmiths and knife smiths is Miki City. Miki is well known to all of Japan for its knifemaking traditions, and its knives and tools recall the pride of Japanese steelmaking. Most Miki manufacturers are small family businesses where craftsmanship is more important than volume and typically produce fewer than a dozen knives a day.
Japanese cutlery design and philosophy
Unlike western knives, Japanese knives are often single ground, i.e., sharpened so that only one side holds the cutting edge. Some Japanese knives are angled from both sides, and others are angled only from one side, with the other side of the blade being flat. It was originally believed that a blade angled only on one side cuts better and makes cleaner cuts, though requiring more skill in its use than a blade with a double-beveled edge. Usually, the right-hand side of the blade is angled, as most people use the knife with their right hand, with ratios ranging from 70/30 for the average chef’s knife, to 90/10 for professional sushi chef knives; left-handed models are rare and must be specially ordered and custom made.
Since the end of World War II, western-style double-beveled edged knives have become much more popular in Japan, the best example being that of the santoku, an alteration of the Gyuto, ( AKA Gyutou) the famous French cooking knife. Even though these knives are often honed and sharpened on both sides, their blades are always given Japanese-style acute-angle slicing edges with an extremely hard temper to boost its slicing capabilities.
Japanese chefs always own their personal knife set, which are never used by other chefs. Some chefs even have two knife sets, which they switch up every other day. After sharpening their knife set in the evening after use, the user will usually let the knife “rest” for a day to restore its “energy” and remove any metallic odor or taste that could possibly be passed on to the meals.