Steels on Tsubame-Sanjo knives
Hardness ranges are typical for kitchen knives, not guarantees; full compositions are on zknives. Sanjo shop labels use their own codes: A = hagane + soft iron (kasumi), B = hagane + stainless cladding.
| Steel | Family | HRC | Character | Marked as | Grit (JIS) | Makers using it |
|---|---|---|---|---|---|---|
| Shirogami #2 (White #2) 白紙2号 | carbon | 60–63 | Hitachi/Proterial Yasuki carbon steel. Easiest to sharpen, takes the finest edge, rusts fast. | 白二 / 白紙 / 白鋼 / 白紙2号 | 1000 → 3000–6000 | Yoshikane Hamono, Hinoura Hamono Kobo, Wakui Bar Hamono, Tsurugi Kenshin, Tadafusa |
| Aogami #2 (Blue #2) 青紙2号 | carbon | 62–64 | White #2 plus chromium and tungsten: better wear resistance, a touch harder to sharpen. | 青二 / 青紙 / 青鋼 | 1000 → 3000–6000 | Hinoura Hamono Kobo, Nakagawa Shokai, Tsurugi Kenshin, Kiryu Kogyo |
| Aogami Super 青紙スーパー | carbon | 64–66 | Longest edge life of the Hitachi carbon steels. Kiryu Kogyo tempers it to HRC 64–65 inside stainless cladding. | 青紙スーパー / 青スーパー / 特青 | 1000 → 3000 (a diamond plate helps) | Kiryu Kogyo, Hinoura Hamono Kobo |
| SK carbon steel SK鋼 | carbon | 58–61 | JIS general carbon tool steel. Cheaper than Yasuki paper steels; Kenshin lists it alongside White steel. | SK / 炭素鋼 | 1000 → 3000 | Tsurugi Kenshin |
| SKD (semi-stainless tool steel) SKD | semi | 62–64 | Cold-work tool steel with ~12% chromium. Yoshikane's signature: stains slowly, sharpens like a carbon steel. | SKD | 1000 → 3000 | Yoshikane Hamono |
| SLD SLD | semi | 62–63 | Hitachi's SKD11-type cold-work steel. Tadafusa's stainless-clad home line and Kenshin's hammered line use it. | SLD | 1000 → 3000 | Tadafusa, Tsurugi Kenshin |
| VG10 V金10号 | stainless | 60–62 | Takefu Special Steel's stainless with cobalt. The default steel of Tojiro's DP/PRO lines; also in damascus lines. | VG10 / V金10号 / V10 | 1000 → 3000 | Tojiro, Kiryu Kogyo, Yajimaya, Shimomura Kogyo, Nakagawa Shokai, Tsurugi Kenshin |
| SG2 / R2 (powder stainless) SG2 / SPG2（粉末ハイス） | stainless | 63–64 | Powder-metallurgy stainless. Long edge life, chips if abused. Kataoka's TAMAHAGANE and Kiryu's SPG2 line. | SG2 / SPG2 / R2 / 粉末 | 1000 → 3000–5000 | Kataoka Seisakusho, Kiryu Kogyo |
| AUS10 AUS10 | stainless | 59–61 | Aichi Steel stainless, often as a clad core in Tsubame factory knives (ROKUSHIRO). | AUS10 / AUS-10 | 1000 → 3000 | Yajimaya |
| CROMOVA 18 クロモバ18 | stainless | 56–58 | Yoshikin's proprietary stainless used in every GLOBAL knife since 1983. | GLOBAL (no steel mark) | 1000 → 3000 | Yoshida Metal Industry |
| Molybdenum-vanadium stainless モリブデンバナジウム鋼 | stainless | 56–58 | Workhorse stainless in Brieto professional knives and household lines from Tsubame factories. | モリブデン / MV | 1000 → 3000 | Kataoka Seisakusho, Shimomura Kogyo, Tsurugi Kenshin |
Care by steel family
Carbon steel (Shirogami / Aogami / SK)
- Rinse and wipe dry immediately after each use — never leave it wet or in the sink.
- Do not put in the dishwasher. Do not cut acidic foods and walk away (lemon, tomato, onion will stain within minutes).
- A grey-blue patina is normal and protective; orange rust is not. Remove orange rust with a rust eraser or #1000 stone slurry.
- Before storing for more than a day, wipe with camellia oil (椿油) or any food-safe oil.
- Store dry, in a saya or on a rack — not loose in a drawer.
Semi-stainless (SKD / SLD)
- Stains slowly rather than rusting fast, but still wipe dry after use.
- No dishwasher. Oil is optional for long storage.
- Holds an edge longer than Shirogami; sharpen on #1000 → #3000 and expect a little more time on the stone.
Stainless (VG10 / AUS10 / molybdenum / CROMOVA / SG2)
- Wipe dry after use. Dishwasher still not recommended — the heat and detergent dull the edge and loosen handles.
- Powder steels (SG2) chip rather than roll: avoid bones, frozen food and twisting cuts.
- Sharpen on #1000; finish on #3000–5000 if you like a polished edge.
Stainless-clad carbon (割込 / 三枚 with carbon core)
- Only the exposed core at the edge can rust. Dry the edge line after use.
- Same rules as carbon for the edge; the cladding forgives everything else.
Kurouchi / black-forged finish (黒打)
- The black scale is a forge finish and protects the blade; do not scrub it off with abrasives.
- Below the black band the polished steel behaves like carbon steel — dry it.
What "White paper" and "Blue paper" steel actually mean
Shirogami (白紙, White paper) and Aogami (青紙, Blue paper) are brand names for the high-purity carbon steels made by Hitachi Metals (now Proterial) at its Yasuki works in Shimane — the Yasuki hagane (安来鋼) family. The names come from the colour of the paper the steel bars were wrapped in at the mill, nothing more.
- White paper is the purest: iron and carbon with phosphorus and sulphur scrubbed out. It takes the keenest edge and is the easiest of all to sharpen — which is why sushi chefs choose it for yanagiba — but it rusts fast. Grades: #1 (hardest), #2 (the standard), #3 (softer, more forgiving).
- Blue paper is White paper with tungsten and chromium added. The edge lasts longer and resists wear; it is slightly harder to sharpen and still rusts. Grades #1 and #2.
- Blue paper Super (青紙スーパー, Aogami Super) adds more carbon, tungsten and molybdenum: the hardest and longest-wearing of the family, and the slowest on the stone.
- Also in the family: Yellow paper (黄紙), a cheaper grade with more impurities, and Silver paper (銀紙 / Ginsan), the stainless branch.
On a blade you will see them as 白二 (White #2), 青二 (Blue #2), 青スーパー or 特青 (Blue Super). All three are carbon steels: wipe the knife dry the moment you finish.
Which one should I buy?
Home cook, first Japanese knife: White #2 in a stainless-clad santoku or gyuto. Easiest to sharpen, forgives a beginner on the stone, and the cladding keeps most of the blade rust-free (Yoshikane, Kinjiro, Tadafusa kurouchi, Kireru Yorokobi).
You cook a lot and hate sharpening: Blue #2 or Aogami Super. The edge lasts noticeably longer (Hinoura, Sadaaki, Tetsuhiro, Kenshin).
You want zero rust care: skip the paper steels — SKD/SLD semi-stainless (Yoshikane, Tadafusa) or VG10 (Tojiro).
Hardness figures are in the table below; compositions on zknives.
How the Yasuki steels relate
Construction compared
| Construction | Sharpness | Edge life | Edge hardness | Chip resistance | Rust | Sharpening |
|---|---|---|---|---|---|---|
| Stainless blade steel ステンレス刃物鋼 | ○ sharp | ○ holds | ○ softer than hagane | ◎ tough | ◎ rust-resistant | ○ easy |
| Stainless core, stainless clad 複合材（ステン割込） | ○ sharp | ○ holds | ○ | ◎ tough | ◎ | ◎ very easy |
| Carbon core, stainless clad 複合材（鋼割込） | ◎ very sharp | ◎ lasts | ◎ hard | △ chips | △ edge line rusts | ◎ very easy |
| Damascus (layered stainless) ダマスカス | ○ sharp | ○ holds | ○ softer than hagane | ◎ tough | ◎ | ○ easy |
| Carbon steel (hagane) 鋼（ハガネ） | ◎ very sharp | ◎ lasts | ◎ hard | △ chips | △ rusts | ◎ very easy |
| Ceramic セラミック | ◎ very sharp | ◎ lasts | ◎ hard | △ very brittle | ◎ never rusts | △ needs diamond |
◎ excellent · ○ good · △ weak. General behaviour of each construction; individual steels vary — see the table above.