A whetstone is a natural or synthetic tool used for the sharpening of tools and blades. Whetstones are one of the oldest human tools, dating back to ancient civilizations. Modern whetstones are often made from synthetic materials, since high-quality natural materials are scarce.
Whetstones have existed in some form nearly as long as bladed tools and weapons. Using an edged tool or weapon results in a gradual dulling that eventually ruins usefulness, as anyone who has attempted to carve a turkey with an old knife can attest to. Whetstones artifacts have been found in the archeological investigations of many Stone Age cultures and later cultures, including in the Roman settlements of the British Isles. Japan has a long and storied tradition with whetstones, thanks to several excellent natural quarries and an robust history with swords and blades.
Whetstones used for basic sharpening are generally flat pieces of stone that resemble small bricks. Those used for tools with complicated edges may be more detailed. Whetstones may be made of many different types of stone, since different grains will result in different sharpening capabilities. Some whetstones are dampened with water or oil, to help wash away the shaved-off pieces of blade.
Originally, these tools were almost always made from natural stone. Quarries in Belgium, Japan, and parts of the United States were highly valued for their production of whetstones. Certain types of stone, such as novaculite, remain highly prized as whetstone material.
Japanese whetstones remain popular for many sharpening needs. Thanks to the natural composition of rock in the islands of Japan, the natural stones have a clay component that make them somewhat softer than other commonly used varieties. This clay is responsible not only for helping to sharpen the blade, but also for adding a brilliant polish and shine to the edge.
Today, many people prefer the more versatile synthetic whetstone, which may be made from ceramic, clay, or particulate matter. Many craftsmen consider these new varieties to be equal to the quality of natural stone, as well as more flexible. Some are double-faced with different surfaces, allowing them to be used for multiple sharpening needs.
One popular type of whetstone, called a diamond plate, uses the extremely abrasive shavings of diamonds as a substitute for other, more common materials. Diamond plate whetstones are also used to keep other types of whetstones flat. As a whetstone is used, it naturally wears down thanks to the same abrasiveness that sharpens the blade. Using a diamond plate to even out the surface keeps regular whetstones in good working order.