Kigami, Yellow Steel, the Working Grade

The third color nobody explains

At the Yasugi works in Shimane Prefecture, billets of different cutlery grades were wrapped in colored paper to tell them apart: white paper (白紙, Shirogami) for the high-purity carbon grade, blue paper (青紙, Aogami) for the tungsten-and-chromium alloyed grade, and yellow paper (黄紙, Kigami) for the standard carbon grade. English-language knife writing covers white and blue exhaustively and then goes silent, as if the system had two colors. It has three, and the third is the one most Japanese households have actually owned.

"Standard" is the operative word, and it does not mean junk. All Yasugi paper steels start from carefully selected high-purity raw materials, a lineage the mill traces to the region's tatara ironmaking tradition (that story lives on the Japanese steel mills page). The ladder Japanese smiths actually use runs: JIS SK commodity tool steel at the bottom, Kigami as the selected grade, Shirogami as the purified grade, Aogami as the purified-and-alloyed grade. On our Steel Family Tree, Kigami is the trunk of the Yasugi carbon branch: the baseline grade from which the white paper line splits off by purity and the blue paper line by alloying.

Yellow vs white: a question of impurity caps

The difference between Kigami and Shirogami is not carbon, hardness, or some secret ingredient. It is the permitted ceiling on two impurities, phosphorus and sulfur, both of which weaken grain boundaries in steel. White paper caps them brutally low; yellow paper caps them slightly higher.

Element	Kigami #2 (Yellow #2)	Shirogami #2 (White #2)
Carbon (C)	about 1.0-1.15%	1.05-1.15%
Silicon (Si)	about 0.15%	0.10-0.20%
Manganese (Mn)	not published in the sources we checked	0.20-0.30%
Phosphorus (P)	0.030% max	0.025% max
Sulfur (S)	0.006% max	0.004% max
Cr / W / Mo / V	none specified	none specified

Read those numbers twice. The gap between yellow and white is 0.005 percentage points of phosphorus and 0.002 of sulfur; both steels are far cleaner than ordinary carbon tool steel. The gap is real (it is why honyaki and top Sakai single-bevels are white, not yellow), but it is a refinement at the margin, not a difference in kind. The steel database zknives puts it plainly: Kigami 2 is pretty much identical to Shirogami 2 except for purity, and the maker's reputation matters more than counting atoms in the alloy.

Kigami #2 and #3, and what survives today

Like the white family, yellow paper historically came in numbered grades, with #2 and #3 the ones that mattered in cutlery and tools:

Grade	Carbon	Status	Best known for
Kigami #2 (Yellow #2)	about 1.0-1.15%	In production; the grade you actually meet	Everyday hocho, entry single-bevels, Tosa outdoor blades
Kigami #3 (Yellow #3)	lower than #2; current figures not published	Largely out of the market	Hatchets, sickles, farm and forestry tools

Japanese sources report that only Yellow #2 remains in regular production today, so "Kigami" on a modern knife almost always means Kigami #2. Older tools in Yellow #3 still circulate in Japan's secondhand and rural tool trade, and some Tosa forges worked both grades for decades. A Yellow #1 appears in some historical grade listings but is effectively absent from the modern market, and we found no published composition for it.

How Kigami actually performs

On the stones

This is carbon steel with no chromium and no hard alloy carbides, so it sharpens the way Shirogami does: fast, clean, honest feedback, a small burr that releases easily. If white steel is the reference sharpening feel, yellow is a very close second, and most hands will not reliably tell them apart blind. That ease of maintenance is exactly why culinary schools and fish processing operations, places where knives are sharpened constantly and abused daily, have long run on yellow steel.

The edge

Kigami takes a genuinely keen edge and supports acute, polished bevels. Typical delivered hardness runs around 58-61 HRC depending on the maker; some retailer charts list conservative figures as low as 56. Many smiths deliberately temper Kigami a touch softer than white steel, trading a little edge retention for toughness in blades that will meet bone, branches, and beginners.

The honest downside

The elevated phosphorus and sulfur ceilings mean slightly weaker grain boundaries than white paper, which shows up as marginally coarser edge behavior and, at equal high hardness, a slightly greater tendency to chip. Edge retention is a small step behind Shirogami #2 and clearly behind Aogami. None of this makes it fragile; it makes it a working steel that expects regular touch-ups rather than a museum edge.

At the forge

Here yellow quietly wins. Kigami is more forgiving in the fire and at the quench than white steel's famously narrow window, which lowers losses, lowers cost, and suits high-volume free forging; Japanese sources note that this easier heat treatment is exactly why it became the standard grade for household knives and all-steel Western-pattern blades. With paper steels the smith is always the spec: a well-treated Kigami #2 will outcut a carelessly treated Shirogami #2 every day of the week.

Tosa, households, and the entry gate to carbon

Kigami's heartland is Tosa, the free-forging blacksmith region of Kochi Prefecture. Tosa smiths build working blades in volume: nata (machete-hatchets), hatchets, kama sickles, hunting and outdoor knives, and rustic kurouchi kitchen knives. For that trade, yellow paper is close to ideal: cheap enough for tools resharpened on a doorstep stone, forgiving enough for high-volume forging, keen enough that a Tosa nata in Kigami #2 embarrasses most Western axes at woodcraft. Tosa forges such as Toyokuni document yellow paper alongside white and blue in their own steel references, which tells you how normal the grade is inside Japan.

In kitchens, Kigami is the entry gate to real Japanese carbon steel. Yoshihiro sells kasumi deba and yanagiba in Yasugi Yellow Steel as their accessible single-bevel tier, Syosaku-Japan runs a dedicated Kigami #2 line, and inside Japan yellow steel has long been the grade of the reliable household bocho and the culinary student's first serious knife.

Care is exactly the white-steel contract: no chromium means it will rust if neglected and patina with use, and the full protocol lives on our Shirogami reference. In practice Kigami blades are lower stress, because so many wear a kurouchi forge finish and cost little enough that the first patina feels like character rather than catastrophe.

Yellow vs white vs blue, side by side

	Kigami #2	Shirogami #2	Aogami #2
Recipe	Selected carbon steel, looser P/S caps	Purified carbon steel	Purified + tungsten and chromium
Edge keenness	Very high	Highest	Very high
Edge retention	Fair to good	Good	Very good
Ease of sharpening	Very easy	Very easy; the reference feel	Easy
Forgiveness at the forge	Highest of the three	Lowest; narrow window	Moderate
Price tier	Budget to mid	Mid to premium	Mid to premium
Signature use	Tosa tools, everyday hocho	Sakai single-bevels, honyaki	High-wear double-bevels

For the full map of where these grades sit among Japan's other cutlery steels, stainless included, see the Steel Guide.

Yellow steel myths, corrected

• "Kigami is cheap junk steel." No. It is a selected Yasugi grade, cleaner than commodity SK tool steel, with the same carbon as White #2. The caps on impurities are looser than white paper's, not absent.
• "Yellow means low carbon." No. Kigami #2 runs about 1.0-1.15% carbon, squarely in White #2 territory. The color codes purity, not carbon.
• "You can feel the impurities on the stones." The difference is subtle at best. Heat treatment and grind dominate; a good Kigami blade sharpens and cuts like good carbon steel, because it is one.
• "Nobody serious uses it." Tosa's professional toolsmiths, Japanese culinary schools, and fish processing kitchens have run on yellow steel for generations. Serious is as serious does.

Kigami questions, answered

What is Kigami (yellow paper steel)?

Kigami (黄紙) is the standard carbon cutlery grade of the Yasugi specialty steel works (Hitachi Metals, now Proterial), named for the yellow paper once wrapped around its billets. It is plain high-carbon steel, about 1.0-1.15% carbon in grade #2, with slightly higher permitted phosphorus and sulfur than white paper steel.

Kigami vs Shirogami: what is the real difference?

Purity, not carbon. White #2 caps phosphorus at 0.025% and sulfur at 0.004%; Yellow #2 allows 0.03% and 0.006%. White takes a marginally finer edge and holds it slightly longer; yellow is cheaper, more forgiving to forge, and nearly identical on the stones.

What knives and tools use Kigami?

Tosa nata, hatchets, sickles, and outdoor knives; everyday Japanese household hocho; entry-tier kasumi single-bevels such as Yoshihiro's yellow steel deba and yanagiba; and workhorse knives for culinary schools and fish processing.

Why is it called yellow paper steel?

The Yasugi works color-coded billet wrappers by grade: yellow for the standard carbon grade, white for the purified grade, blue for the alloyed grade. The paper is long gone; the color names now define the whole classification of Japanese carbon cutlery steel.

Where this data comes from

Grade system and mill background: Proterial (formerly Hitachi Metals) YSS Yasuki Hagane cutlery steel documentation. Yellow #2 composition and impurity comparisons: Sakai Ichimonji Mitsuhide's steel notes and the zknives steel database (Kigami 2 / Hitachi Yellow 2 entries). Production status and grade history: Japanese-language references including Suisin's technical feature on white and yellow steel, the Toyokuni (Tosa) steel composition pages, and SAKURA Japanese Knife's Yasugi steel articles. Usage documentation: maker and retailer materials from Yoshihiro, Syosaku-Japan, and Dellinger. No external links are provided; all figures can be verified against the named sources directly.

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