To obtain a truly sharp edge, you must hand sharpen your Japanese knives with Japanese water stones. The process of sharpening on a stone is not unlike sanding wood; the whetstone scratches away material from the blade in stages to shape and polish the metal to an acute edge. Water stones come in a broad range of grits, from very rough to fine, for this purpose. They are referred to as water stones as water is the lubricant adding the sharpening process. This shows performance at the same level as conventional medium-grade millstone #1200. Heat-binding is used to adhere a super-hard diamond surface to diamond stones, allowing for very quick sharpening. They are highly durable, do not need to be pres-soaked and require only occasional removal of built up metal shavings with a dressing stone. Highly abrasive, they are not recommended for inexperienced users.