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3. Blade Construction & Cladding (San Mai vs. Honyaki)

How Japanese blades are forged: soft protective jackets (stainless or soft iron) around hard cutting cores, plus single-piece Honyaki.

Written by Knife Fit from the sources listed under each entry; not the result of testing. Reviewed 29 Oct 2026. Report a correction

Monosteel / Full Stainless

Solid single-alloy blade with zero reactivity

Crafted from a single uniform sheet of stainless steel from spine to edge (or stainless core with stainless cladding). Zero rust reactivity anywhere on the knife.

Beginner Tip: The lowest maintenance option for busy home cooks, shared kitchens, or rental homes.

Sources: Wikipedia: Japanese kitchen knife

Stainless-Clad San Mai (三枚)

Soft stainless outer cheeks protecting a hard core

Constructed like a sandwich: a hard cutting core (such as Aogami Super, White #2, or SG2) forged between two protective layers of softer stainless steel. Only the exposed 2–4mm along the cutting edge can patina or rust.

Beginner Tip: A common construction for carbon-steel knives: a carbon-steel core forms the edge, and stainless sides cover most of the blade, so the faces of the blade do not rust or stain. The exposed edge of the core still rusts if left wet.

Sources: Wikipedia: Japanese kitchen knife

Iron-Clad San Mai (Soft Iron / 軟鉄)

Fully reactive traditional carbon construction

Both the hard cutting core and the outer protective jacket are reactive iron/carbon steel. The entire blade face will react with acidic ingredients, developing vivid multi-hued patinas (deep blue, amber, gunmetal gray).

Beginner Tip: Loved by seasoned hobbyists for its smooth, tactile whetstone thinning experience and rustic visual evolution. Demands immediate wiping during meal prep.

Sources: Wikipedia: Japanese kitchen knife

Honyaki (本焼 — True Forged Mono-Steel)

Single-piece blade hardened by differential clay quench, as in sword-making

Forged from a single solid billet of high-carbon steel (never laminated). Blacksmiths coat the spine with insulating clay before water-quenching, leaving the edge glass-hard (65+ HRC) and the spine tough, creating a visible temper line (Hamon) like a samurai katana.

Beginner Tip: The quench can crack the blade, which is why honyaki are rare and expensive. They are hard and can chip if mishandled.

Sources: Wikipedia: Honyaki

Warikomi (割込 — Split-and-Insert Lamination)

Traditional core insertion method

An ancient forging method where a hot bar of soft iron or stainless steel is split down the center with a chisel, the hard carbon core steel is inserted into the groove, and the assembly is forge-welded together.

Beginner Tip: Common in traditional artisan workshops (such as Moritaka Hamono). The spine shows the outer jacket wrapping over the top of the core.

Sources: Wikipedia: Japanese kitchen knife

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