Spyderco sharpening tools are made of "High Alumina Ceramic", a U.S.A. made material with the ability to cut any metal known to man. It is formed when alumina particles (synthetic sapphires) are mixed with a ceramic bonding agent. The mixture is shaped and kiln-fired at temperatures in excess of 3000 degrees F for up to three days.

Spyderco ceramics come in three grits - medium, fine and ultra-fine - none of which require lubricants such as oil or water for use. Each grit serves a different purpose in the sharpening process. The medium grit stone produces a good working edge by efficiently removing steel and reshaping the bevel of a dull cutting tool. The fine grit stone then tightens the scratch pattern, creating a razor-sharp edge. A polished and professionally finished edge is achieved with the ultra-fine grit stone. All of our stones are dishwasher and autoclave safe. In addition, steel particles can be removed from any of the stones using a powdered abrasive cleanser and a nylon scouring pad.

The fine and ultra-fine grit stones are "closed-celled" (the particles that make them up are very dense) and will show little or no wear over time. The medium grit stones are "open-celled" (particles are less dense) and will wear only slightly over ti me. Although ceramics are hard materials - measuring up to 9.22 in hardness on the Mohs Scale - they may still be chipped or broken if not handled with care. Please note that our ceramics are guaranteed against manufacturing defects only.