pressure flaking

A technique for shaping a stone edge by pressing, usually with a bone, from the blade edge in toward the "cheek," or the thicker part of the stone being sharpened. The pressure applied to the edge pops off small flakes of stone, narrowing and sharpening the cutting edge being created. The object being sharpened is then flipped over to work the same edge from the other side.

Pressure flaking is intended for refining, not beginning, a sharp edge in stone.