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How to Maintain Your Black Kitchen Knife at Home

Unsure about how to keep the blade of your kitchen knife in top condition? This article will discuss kitchen knife maintenance, including how to sharpen your knife at home safely. Finally, we will explain the distortion and twisting that are common in forged knives, so keep reading for some peace of mind.

Maintenance & Precautions

Learn how to maintain your forged steel kitchen knife for better performance and longevity.

Maintenance Steps

  1. After use, wash the knife with detergent. It is recommended to pour boiling water over the blade before wiping it off. This is because hot water quickly evaporates the water that gets into the invisible fine scratches on the blade, prevents rust, and has a sterilizing effect.
  2. Wipe off any moisture with a dry cloth. Forged steel knives, in particular, are prone to rust, so be sure to always wipe off any and all moisture and dirt whenever you use them. For more information on how to remove rust, please refer to the "How to Remove Rust" section below.
  3. When storing the blade for extended periods, apply commercially available rust-preventive oil for knives (or cooking oil if not available), wipe off the excess, and store the blade.


  1. We recommend using wooden cutting boards whenever possible. Plastic cutting boards may leave invisible chips and scratches on the blade, which can cause it to lose sharpness.
  2. Do not use a dishwasher or dryer, as it may cause the handle to shrink or crack.
  3. Using a knife that is not suitable for a particular application may damage the blade. Therefore, you should always use a knife for its intented purpose. For example, use a thick knife for bones and hard vegetables (such as squash) and a specialized knife for frozen foods.
  4. Do not directly heat the knife over a fire or place it near a fire, as this may cause the blade's hardness to deteriorate or burn the handle.


Sometimes handmade forged blacksmiths' knives become slightly distorted or twisted over time. This is a typical characteristic of these knives and is actually evidence that the blacksmith's work was done well, so there is no cause for concern.

Handmade by blacksmiths using the traditional process of Hon-Warikomi, forged steel knives are individually quenched in a furnace at 1,000 °C and forged with a belt hammer. This differs greatly from stainless steel knives, which are made by die-cutting a flat steel plate. Watch the following video to see what the hammering process looks like.


Due to the nature of iron, slight distortion and twisting occur immediately after the forging process and as it hardens. For quality control, our knives are inspected and adjusted right before shipment after it has hardened. However, distortion and torsion can still occur in rare cases, even after shipment. ”Historically in Japan, professional sharpeners and users alike have corrected distortion by themselves.

If it is absolutely necessary to correct the blade, please ask your local knife shop to do it for you, for your own safety. If you have no choice but to correct the blade yourself, be very careful not to cut your hand. Wrap the blade with a thick paper or cloth, and correct the blade on a non-slip material such as a wooden cutting board, applying force carefully and gradually.

Above: Special wooden rod for correcting distortion (oak) 


What to Do When the Blade Becomes Dull

If the sharpness of the blade starts to deteriorate, sharpen it with a whetstone as soon as possible. The sharpness will be restored. If you cut food with a dull blade, not only will the taste of the food be reduced, but you may also injure yourself from the extra exertion over time. Also, the blade will gradually develop small chips, which will inevitably grow larger.

Grinding stones (whetstones) are available in various grades—rough grit (#80 to #400), medium grit (#700 to #2000), and finishing whetstones (#4000 and up).

Sharpen the blade regularly with a medium grit (#800 or #1000) whetstone once every few uses. As a result, the surface of the blade will stay smooth, allowing you to cut food without damaging the fibers, and bring out the natural flavors.

If the blade is chipped and needs to be repaired, grind the blade with a rough grinding stone until the chip is gone, then attach the blade with a medium grit whetstone. After that, use the finishing whetstone to prepare the blade.

You can find the whetstones you need on our website.


How to Sharpen the Blade

Soak the whetstone in water. It is ready when the air bubbles stop escaping (3 to 5 minutes).
Place the blade of the knife on the whetstone, turning it 45-60 degrees in front of you, and angling it about 15 degrees from the surface of the whetstone. 
Grip the knife with your dominant hand, placing your index finger on the Spine and thumb on the Heel of the knife. 
Place the index and middle fingers of your non-dominant hand along the blade and slide it back and forth while maintaining a 15-degree angle. Grind using the full length of the whetstone. 
Check the blade with your finger. If you see and feel burrs all over, it is a sign that the blade is sharp.
Finally, rub the blade against a stack of newspapers or leather to remove fine burrs and make a smooth cutting edge.


Ilastration:Nihon Keizai Shinbin


How to Remove Rust

If rust appears, you should remove it as soon as possible. If there is only a thin layer of rust on the surface, you can remove it by rubbing a small amount of cleanser on it with a wet corkscrew. If this does not remove the rust, use a rust remover [Sabitoru (Rust-eraser)] and rub with water to remove it.

Find a
Sabitoru (Rust-Eraser) on our website.

If these two methods do not remove the rust, there is a high possibility that it has spread deeper into the steel, so ask your local cutlery shop or sharpener to repair it.

Maintain Your Kitchen Knife with the Right Tools

It is important for the health of your knife and the quality of your cooking to keep your blade sharp. Yoshimune Knives not only offers quality Japanese knives, but the right tools for taking care of them, like our whetstone collection, to ensure the best experience for our customers.