Understanding Carbon Steel: The Soul of Japanese Knives

Carbon steel lies at the heart of Japanese knife-making. Formed by combining iron (Fe) with a modest yet decisive amount of carbon (C), it is this delicate balance that gives rise to blades capable of extraordinary sharpness and character. Unlike stainless steels, which emphasize convenience, carbon steels embody purity and tradition—qualities deeply revered in the world of Sakai’s artisans.

The Role of Carbon Content

The properties of steel change dramatically depending on the carbon content:

• Low-Carbon Steel (Soft Steel): Flexible, easy to work with, but lacking the hardness needed for a keen edge.
• Medium-Carbon Steel: A compromise between toughness and strength, used in general tools.
• High-Carbon Steel: The choice of knife-makers. It can be sharpened to a razor edge and retains sharpness over time.
• Very High-Carbon Steel: Extremely hard, reserved for specialized blades requiring maximum durability.

In broad terms, materials with less than 0.02% carbon are considered iron, while those between 0.02% and 2% carbon fall under the category of steel. Within this range, the magic of knife steel is born.

Yasuki Hagane: The Pride of Japanese Steelmaking

At the pinnacle of carbon steels for cutlery is Yasuki Hagane, produced by Hitachi Metals. This steel carries forward the spirit of the legendary tamahagane once used to forge Japanese swords, reinterpreted for the demands of modern knife-making.

The name “Yasuki” comes from Yasugi City in Shimane Prefecture, where Hitachi Metals established its steelworks. From there, Yasuki Hagane emerged as the defining material for traditional knives, especially in Sakai, where artisans refined its potential through centuries of accumulated craft.

White Steel (Shirogami), Blue Steel (Aogami), and their variations are all forms of Yasuki Hagane—each offering subtle differences in hardness, edge retention, and sharpening feel. To hold a knife forged from Yasuki Hagane is to touch a direct descendant of Japan’s swordsmithing heritage.

More Than a Material

Carbon steel is not merely a composition of iron and carbon—it is the living soul of Japanese blades. Demanding of care yet rewarding with unmatched sharpness, it connects the modern kitchen to traditions stretching back hundreds of years.

To understand carbon steel is to understand why Japanese knives are revered worldwide: they are not just tools, but vessels of history, craftsmanship, and devotion.