Hado Knives

Aogami #1 — Blue Paper #1 — is the higher-carbon sibling of Aogami #2 and the closest blue-paper relative of Shirogami #1. About 1.30 percent carbon, half a percent of chromium, and one and a half percent tungsten put it in a sweet spot: meaningfully better edge retention than the white papers, without the carbide load of Aogami Super.

The cook's experience with Blue #1 is one of balance. It hardens to 63–64 HRC in good hands, sharpens almost as cleanly as a white paper, and holds a refined edge longer because the W- and Cr-bearing carbides resist abrasion. Toughness is modest — these are still high-carbon steels with limited alloy modification — but the steel is well-behaved at the apex and the patina develops more slowly than on a white.

It is less common than Blue #2 or Blue Super in the current market but well loved by knowledgeable users who want the "blue feel" without giving up too much keenness. Look for it in the work of more traditional smiths who run honyaki and clad constructions where the steel's grain refinement can be shown off. Among the makers Modern Cooking carries, Hado Knives works in Aogami #1.

Shirogami #1 — White Paper #1 — is the highest-carbon, highest-purity entry in Hitachi's white-paper family, with approximately 1.30 to 1.40 percent carbon and impurities (P, S, Mn, Si) held to extremely low levels. Without chromium, tungsten, or vanadium, it is the closest thing the modern industrial world has to a continuation of the traditional Japanese tamahagane lineage in commercial form.

In a finished kitchen knife it can run at 64–66 HRC, sharpens to an extraordinary apex on natural and fine synthetic stones, and gives a feel at the cutting board that aficionados describe as glassy. Edge retention is modest — the absence of carbide-forming alloys means the steel is wear-limited — and toughness at this hardness is genuinely low; a thin Shirogami #1 edge will chip on bone or on a poor cutting board. The patina is energetic.

It is the steel of choice for honyaki and high-end clad single-bevels, and it remains the touchstone against which other ultra-clean carbons like 125SC and C130 are judged. Among the makers Modern Cooking carries, Hado Knives and Simon Maillet work in Shirogami #1. Recommend it only to a cook who understands what it is asking of them.