Why are Japanese knives so good? The steel and the forge

When someone asks why Japanese knives are so good, they usually mean a keen edge that lasts. The official craft descriptions give that quality a concrete cause. Many traditional kitchen knives are made by forge-welding a hard carbon-steel cutting edge to a softer iron body, which gives a hard edge together with a tougher supporting layer.^1,9 The hardness does the cutting; the iron absorbs the shock.

The hammer adds to it. Sanjo's craft sheet says forging increases the blade's strength by hammering out any space in the inner part of the metal, resulting in a high degree of strength and abrasion resistance.² The same sheet contrasts hand-hammered blades with modern ones made by stamp pressing and polishing, techniques developed after the second world war.¹⁰ Those are different ways to arrive at a knife shape, and the difference lies in how the metal is treated on the way.

Geometry completes the picture. Sakai's tourism bureau describes single-edged knives whose acute angle gives the cutting edge and a smooth cut plane.¹¹ The Embassy of Japan in Singapore explains that such knives cut fish and vegetables without damaging their fibers or membranes.¹² So a good Japanese knife is a combination: layered steel, hammered metal, careful heat and a deliberate edge.

Whether Japanese steel knives are good depends on which steel you pick. Several kinds cover what a buyer meets, and the Takefu Knife Village explains each in plain terms. Stainless steel clad in stainless is described by its main feature: it rusts little.³ Because the steel is hard, it is a little harder to sharpen than an iron knife but sturdy, and the village recommends it if you choose by ease of care.³⁵

Carbon steel works the other way. It rusts easily, but its greatest advantage is that its sharpness lasts, and it is easier to sharpen than a stainless knife.⁴ After use it should be wiped dry at once and stored with a thin film of oil, which holds rust back a little.³⁶ Sakai's tourism bureau gives the same warning for hand-forged blades: they are weak to water and rust easily.³⁹

Clad steel splits the difference. The village calls carbon steel sandwiched in stainless clad, and says it combines the lasting sharpness of carbon steel with the rust resistance of stainless.⁵ The steel in the middle can still rust, but the outer layers are stainless, so care is easier than with an iron knife.³⁷ If you want a decision rule, it is this: choose stainless for low upkeep, carbon for the longest-lasting edge and clad for a compromise.

Hardness is a heat treatment, not a material. Quenching is an important task that determines the hardness of the blade.⁴³ But a hard blade is brittle and will snap, so tempering is added to give durability and toughness.⁴⁴ Every official craft sheet describes this pair, and the figures are close from region to region.

Sakai City heats the knife to 750 to 800°C and quenches it in water, then reheats it to 180 to 200°C and lets it cool naturally.^6,7 Tosa heats the blade at 770 to 800°C and tempers at about 170°C.^25,29 Echizen hardens at about 800°C and tempers at 150 to 220°C.^26,31 Sanjo quenches at 780°C and tempers at about 50 to 200°C.^27,33

Sakai's craftsmen judge the end of heating by splashing water on the blade and watching how the droplets run.⁴⁵ Sakai City adds that, depending on the type of steel being used, oil may be employed in the tempering process.²⁸ The detail matters because it shows the maker adapting to the steel: the recipe is a framework, not a single fixed program.

The founders of the Takefu Knife Village faced exactly this contrast. They worried about the spread of stainless or cheap punch-out knives made by mass production.⁴⁸ Their response, in 1973, was to establish a study society and, in May 1993, to open a cooperative open factory and direct sales store for 10 companies.^15,18

Today the village lets the public look inside its museum and factory for free, to learn the history of Echizen knives and how they are made.³⁸ It also runs experience programs that the public can join, with advance reservation required.⁴⁹ Seeing a forge at work does more to explain steel than any amount of reading, because the color and sound of the metal tell the story.

For travelers staying in Kyoto, the equivalent is a short session at a working forge. The Kyoto knife making experience lasts 3 hours and starts from $152, and its listing carries 800 reviews at a rating of 4.8. Ask the smith which steel you are working and which bevel the finished blade carries; the answers apply everything in this guide to the knife in your hand.