Shirogami #1 (White Paper Steel No. 1) is the most carbon-rich and purest grade in the White Paper series by Hitachi Metals. It represents the absolute peak of attainable sharpness in Japanese cutlery.
It is often called the "ultimate professional steel" because it is extremely difficult for blacksmiths to heat-treat correctly, and equally demanding for the user to maintain.
Key Characteristics
The Sharpest Possible Edge: Due to its extremely high carbon content and lack of alloying elements, Shirogami #1 can be sharpened to a "finer" point than almost any other steel in existence. It is the gold standard for precision tasks like slicing sashimi.
Highest Hardness: It can reach a hardness of 64–65+ HRC. This makes the edge incredibly rigid, allowing for very thin and acute edge geometries.
Extreme Brittleness: This is the most brittle of the White Paper steels. It has almost zero impact resistance; if the edge hits a bone, a seed, or a hard cutting board, it is highly likely to chip or shatter.
Incredibly High Reactivity: With zero Chromium, it is "naked" carbon steel. It will rust or discolor almost instantly if exposed to moisture or acidic foods.
Purest Sharpening Feel: Because there are no carbides like Tungsten or Vanadium to get in the way, it feels like "butter" on a whetstone. It responds instantly to sharpening, allowing for a perfect mirror-polished edge.
Chemical Composition
Shirogami #1 is defined by its simplicity and high carbon:
Carbon (C): 1.25% – 1.35% (The highest in the White Steel series).
Manganese (Mn): 0.20% – 0.30% (Small amount for stability during forging).
Phosphorus & Sulfur: Kept to extreme minimums to ensure maximum purity.
Common Applications
Honyaki Knives: It is the most common choice for "True-Forged" (Honyaki) blades, which are the most expensive and difficult-to-make Japanese knives.
Yanagiba (Sashimi Knives): Where the goal is to slice raw fish with zero cell damage to preserve flavor and texture.
Top-Tier Woodworking Tools: Specialized Japanese chisels meant for final finishing cuts on softwoods.
Shirogami #1 vs. Shirogami #2
Shirogami #1: Higher hardness and sharpness, but much more brittle and difficult to find (only elite smiths use it).
Shirogami #2: The "standard" professional choice. It is tougher and easier to work with while still being sharper than almost any Western knife.
Shirogami #1 vs. Aogami Super
Shirogami #1 wins on pure sharpness and ease of sharpening.
Aogami Super wins on edge retention (staying sharp longer) and durability.