Natural Coticule Stones From Belgium
The Ardennes region of Belgium has, for centuries, produced natural coticule stones famous as high quality whetstones. Sought after by Straight Razor Sharpeners, Woodworkers, Carvers and Leather Workers, these natural stones are not as abundant as they once were. A single quarry is still in operation in Belgium, hand producing these wonderful natural sharpening stones.
This particular type of whetstone is called a Coticule. They are characterized by a high concentration of spessartite garnets, and have a characteristic white-yellow color. They are fixed to a backing of blue-gray slate for stability. Coticules are somewhat brittle, and the slate backing prevents breakage. The slate is intended for structure only and is not used in the sharpening process.
Note that Coticules are hand shaped, natural stones. The presence of hairline fractures is normal and not considered a defect. Some variance of size, color and exact composition is also normal.
A Unique Sharpening Experience
If you are used to using modern synthetic or even natural Arkansas stones, you will find sharpening with a Coticule to be a bit different, but very satisfying.
Single Stone Sharpening
While they are often compared to Japanese water stones of up to 16000 grit, Coticules can actually be used as if they were multiple stones of varying grit. Altering the amounts of water and pressure used while sharpening will make the stone more or less aggressive.
Coarser sharpening is achieved by using less water and greater pressure. The garnets in the stone break free and create a slurry when used in this fashion. In the slurry created on a Coticule, the hard garnet particles are able to abrade more deeply as they roll freely on the surface of the stone, resulting in a more aggressive action that will leave a cloudy finish on the metal.
You can achieve an even finer sharpening by reducing the thickness of the slurry and by gradually adding more water and reducing the amount of pressure used. Eventually, the slurry is thinned to the point where only water will be present on the surface of the stone. With fewer garnets rolling freely on the surface of the stone, the individual particles cannot bite as deeply. At this point, using almost no downward pressure on the edge against the stone, the result is a mirror-fine finish on the metal.
Coticule Stones are related to and found alongside Belgian Blue Whetstones. While both types are often used as stand alone sharpening stones, the BBW's are sometimes used for initial coarser sharpening before finishing with a Coticule.
Use With Water
Coticule Stones should only be used with water, never oil. They are non-porous and do not absorb liquid or clog with swarf, so there is no need to soak them prior to sharpening.