【Reading】しあげといし

【English Name】Finishing Whetstone

The process of sharpening blades has stages, and the whetstone used for the final finish is the finishing whetstone (shiageto). Of the three categories—coarse, medium, and finishing—the finishing stone has the finest grit and is used to polish the surface of the edge smooth. With synthetic stones, those of grit #2000 and above are generally called finishing stones, but there is no clearly defined standard, and the classification varies among users.

In the sushi setting, a knife's sharpness directly governs the quality of the work. By forming the outline of the edge with coarse and medium stones and finally polishing with the finishing stone, the cut surface of sashimi becomes smooth, achieving cuts that preserve the material's inherent freshness and texture. For this reason, daily sharpening with a finishing whetstone is an essential habit for chefs.

By raw material, they divide into two lineages: natural stone and synthetic product. Natural finishing stones use slate (mudstone) as their parent rock, and those rich in fine quartz particles derived from radiolaria have been regarded as high quality. Because of the gentle feel when sharpening and excellent durability of sharpness, many chefs favor them. Synthetic whetstones, since production began in 19th-century America, became widespread thanks to the advantages of uniformity and easy availability. The representative abrasive grain used in finishing stones is white alumina (WA), generally combined with magnesia-based or resin-based binders.

Because repeated sharpening creates a hollow in the surface of the stone, the corrective work of flattening the surface again is also an important part of maintenance.