Steels of Choice
For the toughest-performance blade that holds a sharp edge, high-carbon steel is used. By itself, high-carbon steel will discolor and rust. The most common steel used in high-quality kitchen cutlery is high-carbon stainless steel. It is rugged; resists watermarks, rust, and discoloration; and maintains a sharp edge. Surgical stainless steel is the most resistant to watermarks and rust, due to its composition of less carbon and more chromium in the alloy. Surgical steel is not as hard as high-carbon stainless steel and does not stay sharp as long.
Blocked or Forged
Blocked blades are cut from sheets of steel, like cutting cookie shapes. Blades are then ground and edged. These are lightweight, inexpensive cutlery blades that lack balance. Forged steel starts with a chunk of steel, which is heated and pounded into shape for superb performance. Forging can be done by hand or machine. After shaping, the steel is heated to its critical point and quenched to harden the metal. Japanese kitchen cutlery uses an alloy and heat treatment that produces a harder, thinner, forged blade.
Zirconium oxide (ceramic), used in kitchen knives, is so hard it maintains a razor-sharp blade for years. These ceramic knives must be used on a cutting board - ceramic blades will cut into serving platters and dishes. When sharpening is required, it must be done with diamond sharpening tools.
Titanium holds an edge as well as steel and contains carbides (a compound of carbon and metal) that allow the blade to be heated to achieve the desired hardness. The result is kitchen cutlery that holds its edge and is more flexible than steel. This is a superb quality in a filet knife. Unlike steel knives, titanium kitchen cutlery does not transfer the flavor of the metal to foods.