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Sharpening a Japanese knife

Japanese knives should only be sharpened with so-called water stones. Japanese water stones must be placed in a water bath for about 5-10 minutes before use to prepare the surface of your water stone for sharpening. However, at the same time we are convinced of bench stones, which only need to be moistened with water on the surface and can therefore be used immediately. You can find this information in the respective product descriptions of the grinding materials. Both types of stone should never be used without water, otherwise the special properties will not be effective. During grinding, there should also always be a small layer of water on the stone, oil should not be used.

How to sharpen a Japanese knife?

Japanese knives should always be sharpened with a water whetstone.

Two characteristics are decisive in the selection of the water stone. The first is the grain size, and the second is the bond structure. The larger the grains, the more abrasion can be achieved on your knife. The higher the bond hardness, the lower the material abrasion on the water stone. For coarse grinding work on high-quality Japanese kitchen knives, grit sizes of JIS 700-2000 are ideal. For polishing and final grinding, grit sizes of JIS 3000 - 10000 are recommended. For the conversion from FEPA to JIS you can use the table below. As a rule, two grinding stones are sufficient for normal maintenance. If a stone is needed to grind out broken blades, a grit size of approx. JIS 220 can be used.

Blade shapes of japanese knives

In order to apply the correct technique when sharpening, it is essential to pay attention to the blade shape. Depending on the grind of the knife, choose method 1 or method 2. These methods are described below. Method 1 should be chosen for blades ground on both sides, method 2 for blades ground on one side. Blade sharpening can be learned quickly using the three senses of sight, touch, hearing and a little practice and is not as difficult as you might think.

Grinding stone geometry

Your whetstone should always be flat when you resharpen your knives. Over time, your waterstone can wear and the effect of hollow grinding occurs. The surface becomes uneven and your knife cannot be laid flat. Depending on the bond hardness, this happens sooner or later. You can easily remedy this by placing a second water stone on top to even out the unevenness. Since Japanese waterstones are usually made with low bond hardness, this is the most convenient solution. Alternatively, you can use a special sharpening stone dressing block that can restore an even surface even with high bond hardness.

Method 1

Your knife has a cutting angle determined by the manufacturer, which should be maintained. This is usually 10°-17°. Try to achieve this angle by holding your knife by the handle with one hand and placing the knife on the water stone flat to a cutting edge. As soon as you have found this cutting angle, fix it with the other hand. With this starting situation, you can now move the knife in the indicated direction of movement. Make sure that the entire length of the blade is processed in this way. Repeat this process on the second cutting side. As soon as you have ground a noticeable burr on both sides, switch to a finer grit and give your knife a fine grind. The fine grind removes the burr on both sides. With a little practice, you will quickly notice if the sharpening feels right or if the contact angle is off. Also, by listening carefully, you can determine over time if your grinding attempt is producing the desired result.

Method 2

Again, the secret is to find the right cutting angle of your knife. However, this method is only used for knives with a blade ground on one side. However, if the knife is plated on the unsharpened side, the knife should not be drawn across the entire stone. In this case, you should only grind on the edge of the stone up to the plated area, otherwise you may scratch the blade. In the first step, find the cutting angle again and place the blade flat on the water stone at the bevel angle. Fix the knife with one hand on the handle and search for the cutting angle by tilting the knife. Once you have found the cutting angle, use your other hand and place it on the blade to fix it. Now move the knife in the direction of movement and again make sure to work the entire cutting edge. As soon as you feel a ground burr again, you can turn the knife and place it on the water stone. Please use a water stone with a small grain size for this step to avoid scratching your blade. Once the burr is removed, you can test your result on a tomato or a piece of paper, for example, and repeat the described sharpening steps if necessary. As a rule of thumb, we recommend that you grind the side of the blade with the cutting angle about 9 times as often as the flat side.