waterstone

A waterstone, also known as a water stone, is a sharpening stone that uses water as a lubricant and cooling medium during sharpening. The stone’s abrasive particles are bonded in a matrix, and blades such as knives and chisels are ground against it to remove metal and form a sharp edge. Waterstones are typically made from synthetic materials—often silicon carbide or aluminum oxide—or from natural stone sources. They come in a range of grits and are commonly used in both professional and hobbyist knife and tool maintenance.

Two main categories exist: synthetic waterstones and natural waterstones. Synthetic waterstones offer consistent grit and faster cutting, with common grits spanning roughly from coarse (around 200–800) to mid-range (about 1000–3000) and finishing (3000–8000). Natural waterstones, such as traditional Japanese stones, vary in hardness and slurry behavior and are prized for their fine finishing capabilities. Users may progress from rough grits to finer grits to achieve a sharp edge with a polished feel.

Care and use: many waterstones require soaking in water for several minutes before first use, though some “splash-and-go” varieties do not require extended soaking. During sharpening, water is applied to prevent overheating and to wash away debris, while a light slurry helps polish the edge. Maintenance includes regularly flattening the surface with a lapping plate, cleaning after use, and drying thoroughly to prevent mold or degradation. Proper storage away from humidity helps prolong life.

Waterstones are distinct from other sharpening media and should not be confused with Waterstones, a former UK book retailer. See also sharpening stones and blade maintenance.