Japanese Knife Steel Explained: White, Blue, VG-10 and More

Shop for a Japanese knife and the listings stop talking about shape and start talking in code: Shirogami #2, Aogami Super, VG-10, SG2, HRC 61. It reads like a spec sheet because it is one — but underneath the jargon there are only a few real decisions. Here is what the names mean, where they come from, and how to pick a steel you’ll be happy to live with.

The short answer

• The first choice is carbon or stainless, not which brand of steel. Carbon steel sharpens beautifully and rusts; stainless forgives a damp draining rack. Decide that first.
• “White” and “Blue” are carbon steels from one Japanese steelmaker. White is the simpler, easier-to-sharpen one; Blue adds alloying elements for a longer-lasting edge.
• VG-10 and SG2 are stainless steels. VG-10 is the familiar all-rounder; SG2 is a harder powder steel for people who sharpen well.
• Construction matters as much as the steel. Most Japanese knives are a hard cutting core wrapped in softer metal — and what that outer layer is made of decides how much rust you’ll be wiping.

Carbon or stainless: the real choice

Every Japanese knife steel falls into one of two families, and the difference shows up in your kitchen every day.

Carbon steel — hagane (鋼) in a Japanese knife shop — is iron and carbon with little else. It takes a very keen edge and responds quickly on a whetstone. It also rusts: leave it wet, or sitting on a cut lemon, and orange spots appear. With daily use and drying it builds a grey-blue patina that helps protect it.

Stainless steel adds a good deal of chromium, which is what keeps it from rusting in ordinary use. The trade-off, historically, was an edge that felt a little less crisp and was a little slower to sharpen. Modern Japanese stainless steels have closed much of that gap.

If the knife will be shared by a household, left on a draining rack, or used by someone new to Japanese knives, start with stainless. If you enjoy the ritual of wiping a blade dry and want the most responsive edge on the stone, carbon is worth the attention. Our knife care guide covers the daily habits for both.

The paper steels: Shirogami and Aogami

The most famous Japanese carbon steels come from Yasugi in Shimane Prefecture — a region its steelmaker describes as renowned for the purity of its iron sand, and tied to the old tatara method of smelting that sand into steel. The Yasugi works, once part of Hitachi Metals and now run by Proterial, sell these steels under the name YSS Yasugi Specialty Steel.

Their knife grades carry odd names — White Paper, Blue Paper — and the explanation is literal. The finished steel was told apart by the colour of paper attached to it, and the colours stuck as names.

• 白紙 Shirogami (White Paper steel) — a high-purity carbon steel with almost no alloying elements. It is graded #1, #2 and #3 by carbon content, #1 having the most. White steel takes an extremely fine edge and is pleasant to sharpen; the cost is that it can chip if abused and loses its edge sooner than the alloyed steels.
• 青紙 Aogami (Blue Paper steel) — White steel with chromium and tungsten added. The alloying makes the edge wear more slowly, so it stays sharp longer between sessions on the stone. Tojiro, the Tsubame-Sanjo knife maker, describes it as hard to wear down and long-cutting.
• 青紙スーパー Aogami Super — Blue steel pushed further, with more carbon plus molybdenum and vanadium. Very hard and very wear-resistant; makers also warn it is more demanding to sharpen and still rusts. A steel for people who already sharpen confidently.

You may also see 黄紙 Kigami (Yellow Paper), a more modest carbon grade that Tojiro notes is used for household Japanese knives and all-steel Western-style knives.

The stainless names you’ll see

• Molybdenum-vanadium stainless — the workhorse of good everyday Japanese knives. Tougher and more wear-resistant than basic stainless, easy to sharpen, and hard to hurt. Often simply labelled “molybdenum steel”.
• 銀三 Ginsan (Silver #3) — from the same maker as White and Blue, a stainless that knife makers praise for being unusually easy to sharpen for a stainless. A good choice if you want stainless but a carbon-like feel on the stone.
• VG-10 — developed by Takefu Special Steel in Echizen, Fukui, one of Japan’s knife-making towns. The maker lists it at about 15% chromium, 1% molybdenum and 1.5% cobalt, with a little vanadium, and describes it as combining corrosion resistance with sharpness. Tojiro’s honest summary: slightly behind carbon steel for sheer bite, but much more rust-resistant. It is a common core steel in clad, patterned-surface knives.
• SG2 / R2 — also from Takefu, and a different kind of steel. It is made by powder metallurgy, pressing and sintering fine steel powder rather than casting a molten ingot, which allows more alloying and a finer structure. The result is a hard stainless (Takefu specifies HRC 62 or more) that holds its edge a long time. The two names refer to the same material.

If you’re curious where much of this steel ends up, Echizen and Seki are good places to start.

What the hardness number means

Listings often give a number like HRC 60. That is Rockwell C hardness: higher means harder. A harder edge can be ground thinner and stays sharp longer, but it is also more brittle — more likely to chip on bone, a frozen block, or a glass board — and it takes longer to sharpen.

As one maker’s reference point, Tojiro gives these working hardnesses for its own knives:

Treat these as one maker’s figures, not fixed properties of the steel. Hardness comes from heat treatment, and another smith can harden the same steel a point or two higher or lower — which is why the same named steel can appear with different HRC figures from different makers.

Core and cladding: how the knife is built

Very few Japanese knives are one piece of steel all the way through. The usual approach is to put a hard cutting steel only where the edge is and surround it with something softer and tougher.

• Kasumi (霞) or awase — the traditional single-bevel construction: a hard steel edge forge-welded to a soft iron body. Tojiro explains the name — “mist” — comes from the hazy look of the soft iron beside the bright steel on the bevel. Tough, forgiving and easy to repair; it is the usual build for traditional single-bevel knives (see deba, yanagiba and usuba).
• Honyaki (本焼) — the whole blade is one hard steel, hardened in a way similar to a sword. Harder and very fine-cutting, but expensive, harder to make and to repair, and less forgiving in use. Our Sakai guide has more on how these are made.
• Sanmai (三枚合わせ) and warikomi (割込み) — the double-bevel versions: a hard core sandwiched between two softer outer layers. In sanmai three layers are laminated; in warikomi the soft steel is split and wrapped around the core. For a home cook the effect is similar.

The practical point is the outer layer. A blue or white steel core wrapped in stainless cladding gives you a carbon edge where it counts, while the flat of the blade resists rust — only the thin strip at the very edge needs watching. Wrapped in soft iron, the whole blade will rust and patina. Listings usually say which; if a carbon-steel knife is going to a first-time owner, stainless cladding is a kind choice.

How to choose

One honest rule underneath the chart: the steel matters less than whether you keep it sharp. A well-kept molybdenum knife will out-cut a neglected Aogami Super every day of the week. Pair whichever steel you choose with a good whetstone and the habit of using it.

Still deciding on a shape? Start with gyuto, santoku or nakiri. Or browse hand-picked, Japan-shipped blades on The Table.

Sources & Further Reading

• Tojiro — Knife Materials (Japanese) — The Tsubame-Sanjo maker’s overview of carbon, stainless, VG-10 and powder steels, with the working hardness it uses for each.
• Tojiro — Honyaki and Kasumi (Japanese) — How a one-steel honyaki differs from a steel-and-iron kasumi blade, where the “mist” name comes from, and the trade-offs of each.
• Takefu Special Steel — VG10 — The Echizen steelmaker’s own specification for VG-10: chromium, molybdenum, cobalt and vanadium content, hardness and intended uses.
• Proterial — YSS Yasugi Specialty Steel — The maker of White and Blue Paper steels on its Yasugi works, the region’s iron sand, and the tatara tradition behind them.