Öljykiviä

Öljykiviä, a Finnish term, translates to "oil stones" in English and refers to natural stones used for sharpening tools, particularly knives and other cutting implements. These stones are typically composed of fine-grained sedimentary rock, often silicon carbide or other abrasive minerals, bound together by a natural matrix. Historically, various types of sedimentary rocks were used, with their effectiveness depending on the grit and composition.

The sharpening process with an oil stone involves placing the cutting edge of the tool against the stone's surface and moving it back and forth in a controlled manner. A lubricant, traditionally oil but sometimes water or honing fluid, is used to prevent the stone from becoming clogged with metal shavings and to aid in a smoother sharpening action. The oil also helps to carry away debris, ensuring a cleaner cut and a finer edge.

Different grades of oil stones exist, ranging from coarse for repairing damaged edges or quickly removing material, to fine for polishing and achieving a razor-sharp finish. The choice of stone depends on the type of tool being sharpened and the desired level of sharpness. While modern sharpening systems are widely available, oil stones remain a popular choice for many due to their effectiveness, durability, and the tactile feedback they provide during the sharpening process. They are valued for their ability to produce a superior edge when used correctly.