Japanese Blue and White Steel
The most widely available Japanese tool steel is manufactured in two forms: blue steel and white steel Ė named for the color of the wrapping paper used by the maker. Knowledge of these two formís chemical content and tempering process allow the woodworker considering Japanese edge tools to make some tradeoff between hardness and toughness in the bladeís edge qualities. Hardness means the temper and content of the metal is such that the blade can be sharpened to a very fine degree but results in a somewhat brittle edge prone to chipping or crumbling. Toughness refers to the ability of the edge to avoid damage, and thus stay sharp longer.
Blue steel, or Aogami, has tungsten and chromium alloys added to the edge steel that make the hardening temperature less important, resulting in an edge that tends to be tougher, and thus stay sharp longer than white steel, while not taking on as fine an edge. White steel, or Shirogami, contains fewer impurities and does not have the alloys added, so the hardening temperature range is very narrow. The blacksmith forging white steel has to be very skilled, but the result is tool steel that can be sharpened to a very fine, but more brittle, edge. Both forms are further broken down into grades based on the carbon content of the steel.
The better Japanese blades are laminated by hammer welding the edge steel onto an iron or softer carbon steel core, the actual process proprietary to each blacksmith. So, while there is science in the forging, hammering, heat treating and tempering processes, more than anything else the quality of the steel is the result of the care and skill of the blacksmith. These are family run businesses that trace their lineage back to the edged weapon makers to the samurai and it takes 10-15 years at minimum to perfect the craft. Considering this learning curve, it is no small wonder that Japanese blue and white steel blades made by traditional methods are superior to machine manufactured products.
When trying to decide which blade to buy in a Japanese tool you should bear in mind the difference between blue steel, white steel, or the exemplary special process steels like Damascus, is not one of quality. There is a wide range of qualities available in both types of steel, and in the chisels made with from these steels. You can get acceptable toughness in very hard white steel chisels while taking advantage of that formís ability to yield a very sharp edge; or you can get a quality blue steel blade that can be honed and sharpened very finely. And of course it is quite easy to get neither hardness nor toughness in a substandard steel blade, blue or white, from an inept or sloppy manufacturer. The chisels that we are offering are all at the higher end of what is available. It really boils down to the quality of the steel and the skill and care of the blacksmith. So, consider the edge qualities you want in a chisel and buy your Japanese edge tools from a trusted source. Either form of steel in a quality tool will yield outstanding results.