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Sharpening stones, water stones or whetstones are used to grind and hone the edges of steel tools and implements. Examples of items that may be sharpened with a sharpening stone include scissors, scythes, knives, razors and tools such as chisels, hand scrapers and plane blades. Though it is sometimes mistaken as a reference to the water often used to lubricate such stones, the word "whetstone" is a compound word formed with the word "whet", which means to sharpen a blade, not the word "wet". The process of using a sharpening stone is called ''stoning''. Sharpening stones come in a wide range of shapes, sizes and material compositions. Stones may be flat, for working flat edges, or shaped for more complex edges, such as those associated with some wood carving or woodturning tools. They may be composed of natural quarried material, or from man-made material. Stones are usually available in various grades, which refers to the grit size of the particles in the stone. Generally, the finer the grit, the denser the material, which leads to a finer finish of the surface of the tool. Finer grits cut more slowly because they remove less material. Grits are often given as a number, which indicates the density of the particles with a higher number denoting higher density and therefore smaller particles. ==Natural stones versus artificial stones== The use of natural stone for sharpening has diminished with the widespread availability of high-quality, consistent particle size artificial stones. As a result, the legendary Honyama mines in Kyoto, Japan, have been closed since 1967. Belgium currently has only a single mine that is still quarrying Coticules and their Belgian Blue Whetstone (BBW) counterparts.〔http://www.coticule.be/faq-reader/items/how-does-a-belgian-blue-whetstone-compare-to-a-coticule-40a-story-about-garnets41.html〕 This scarcity causes high prices for a good quality natural stone. Lower quality natural stones have problems with consistent grain sizes, low abrasive particle content allowing only slow sharpening, inconsistency in hardness, inclusions of large particles of other stone materials, and cracks and other natural imperfections. Modern synthetic stones are generally of equal quality to natural stones, and are often considered superior in sharpening performance due to consistency of particle size and control over the properties of the stones. For example, the proportional content of abrasive particles as opposed to base or "binder" materials can be controlled to make the stone cut faster or slower, as desired. Natural stones are often prized for their natural beauty as stones and their rarity, adding value as collectors' items. Furthermore, each natural stone is different, and there are rare natural stones that contain abrasive particles in grit sizes finer than are currently available in artificial stones. One of the most well-regarded natural whetstones is the yellow-gray "Belgian Coticule", which has been legendary for the edge it can give to blades since Roman times, and has been quarried for centuries from the Ardennes. The slightly coarser and more plentiful "Belgian Blue" whetstone is found naturally with the yellow coticule in adjacent strata; hence two-sided whetstones are available, with a naturally occurring seam between the yellow and blue layers. These are highly prized for their natural elegance and beauty, and for providing both a fast-cutting surface for establishing a bevel and a finer surface for refining it. This stone is considered one of the finest for sharpening straight razors. The hard stone of Charnwood Forest in northwest Leicestershire, England, has been quarried for centuries,〔Ambrose, K et al. (2007). ''Exploring the Landscape of Charnwood Forest and Mountsorrel''. Keyworth, Nottingham: British Geological Survey〕 and was a source of whetstones and quern-stones. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sharpening stone」の詳細全文を読む スポンサード リンク
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