This medium grinding stone is molded with a mixture of abrasive(alumina) and bonding(phenol resin)agents, then fired at moderate temperature(approximately 120-200℃).Just add water and the grinding stone can be used right away. The composite is a natural grinding stone. Since it is hardened at moderate temperature, the abrasive and bonding agents are still effective. As a result, the stone could be damaged if left for long periods(several years or up to a decade), or if it is stored while wet. Also, a half-sharpened knife left to sit could start to rust, so after sharpening, be sure to rinse and wipe the knife. This finishing stone has very fine grit that allows for a beautiful shine. If used after an intermediate stone, the difference in granularity is substantial, and quite a bit of time will be required. Using a #2000-3000 grit stone in between steps can more quickly create a very attractive finish. This is an "all powerful" grinding stone fit for any kind of culinary knife.