Natural Oilstones
Natural oilstones have been used for centuries as a sharpening medium for tools used in a variety of industries. Natural oilstones are typically composed of either mineral-rich materials such as novaculite or a combination of metals such as aluminum oxide, iron, and chromium. Both varieties can produce an exceptionally sharp edge when well maintained and regularly used, making them an ideal choice for tool sharpening.
Novaculite is the mineral most commonly used for natural oilstone production. It has a unique composition of silicon dioxide, aluminum oxide, and iron oxide that it forms naturally through a long period of geological processes, such as extreme heat and pressure. Novaculite exhibits low permeability and a high degree of abrasion resistance, making it the perfect material for use in oilstones.
Oilstones constructed of aluminum oxide, iron, and chromium are known as synthetic or combination oilstones. These stones are made in a factory, usually in a two-step process. First, the aluminum oxide, iron, and chromium powders are mixed together and heated in order to make a mixture of molten metal. Then, the mixture is poured into a mold to form the oilstone. Synthetic oilstones are typically harder than their natural counterparts and can last longer when taken care of properly.
Unlike the process of sharpening an edge with a whetstone or a grinding wheel, the sharpening process with an oilstone is a slower and more elaborate process. Firstly, a mineral or synthetic oil must be applied to the stone in order to prevent any metal particles from scuffing or scratching it. Then, the tool is positioned at a certain angle on the oilstone and rubbed in circular motions until an adequately sharpened edge is achieved. With regular use, the oilstone will become smoother and any minor imperfections on the surface will be ground away, making the sharpening process even easier.
Regardless of whether a natural or synthetic oilstone is chosen for sharpening tools, understanding the proper way to use them is essential. Both types require frequent re-oiling and must be protected from liquids and debris that could cause them to rust or deteriorate over time. Once the correct sharpening angle and technique are memorized, a well-maintained oilstone can produce a consistently sharp finish with little effort.
