Guide in Using Toishi - Japanese Whetstones

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 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. The Japanese traditionally used sharpening stones lubricated with water (using oil on a waterstone reduces its effectiveness). They have been doing this for many hundreds of years, and the first stones were naturally occurring. The geology of Japan provided a type of stone, which consists of fine silicate particles in a clay matrix. This is somewhat softer than Novaculite. These softer Japanese stones have a few advantages over harder stones. First, because they are softer they do not become glazed or loaded with the material they are sharpening. New particles are constantly exposed as you work with them and thus they continue to cut consistently. Second, they can be lubricated effectively with water (rather than oil, which can ruin the stone) so nothing but water is required. Finally, because they are soft, the worn material and the water form a slurry that in conjunction with the stone, sharpens and polishes the blade. A disadvantage is that they become uneven faster than other types of sharpening stone, although at the same time this makes them easier to flatten.

Japanese knives should be sharpened regularly to fine-grained rocks and withdraw water. Please don’t use any sharpening steel. Due to the special hardness of the blade, the sharpener does not sharpen the knife properly and may even damage the blade. Before using the stone place it in the water for a short period of time. After about 10 minutes put the stone on a non-slip surface. Take the knife firmly in hand. Put the knife in the upper third of the blade on the stone and press with your left hand the blade securely in accordance with their Grinding Angle. Now grind the blade through even up and down movements. Away from the body exert more pressure as the pulling back towards you. Check between the loops, if a ridge has formed. Now, with the middle third of the blade in the same way, grind more with the lower third, until you sensing a burr on the blade. Now for the back of the blade, grind. Here lay the blade almost flat on the stone and the ridge, which has resulted in grinding the front of the blade away. Burrs must be removed in any case, since otherwise the cutting edge does not have a really sharp and pointed Schittwinkel. Grind single-edged knife only on the Anschliffseite. Both sides ground blade, 60% of sharpening features on the front, and 40% on the back. Please let the stone after use to dry thoroughly and evenly and keep it in a dry place. Ask the Wasserstein before drying in the sun, as it may well become unusable.

Whetstones may be natural or artificial stones. Artificial stones usually come in the form of a bonded abrasive composed of a ceramic such as silicon carbide (carborundum) or of aluminium oxide (corundum). Bonded abrasives provide a faster cutting action than natural stones. They are commonly available as a double-sided block with a coarse grit on one side and a fine grit on the other enabling one stone to satisfy the basic requirements of sharpening. Some shapes are designed for specific purposes such as sharpening scythes, drills or serrations. Historically, there are three broad grades of Japanese sharpening stones: the ara-to, or "rough stone", the naka-to or "middle/medium stone" and the shiage-to or "finishing stone". There is a fourth type of stone, the nagura, which is not used directly. Rather, it is used to form a cutting slurry on the shiage-to, which is often too hard to create the necessary slurry. Converting these names to absolute grit size is difficult as the classes are broad and natural stones have no inherent "grit number". As an indication, ara-to is probably (using a non-Japanese system of grading grit size) 500–1000 grit. The naka-to is probably 3000–5000 grit and the shiage-to is likely 7000–10000 grit. Current synthetic grit values range from extremely coarse, such as a 120 grit, through extremely fine, such as 30,000 grit (less than half a micron abrasive particle size).