GUIDE: Maintenance of Kitchen Knives

After long use, every blade will become dull. Blade wear depends on the quality of steel, usage and maintenance of the blade. This guide describes the correct usage and maintenance of any kitchen knife (not just Japanese) in order to extend its lifespan and enjoy a sharp blade all the time.

Regular Sharpening

A sharp knife is a safe knife. The sharper the knife, less chance to get cut. It will follow our hand movement and won't slip easily. A sharp knife will damage the cells of our food less, meaning the ingredients will stay fresh longer and preserve more taste when cooking.

Knife sharpening is not a difficult task. We are big supporters of the idea that everyone should learn how to sharpen a knife. We advise to invest a little bit of your time and learn sharpening technique. It only takes some practice and you can't really damage the knife. Once you get some grip it shouldn't take more than 10-15 minutes to sharpen a knife.

Check out our step-by-step Knife Sharpening Video Guide for Beginners:

How often do I need to sharpen my knives?

Short and simple: whenever you feel your knives are not cutting as good as you would want them to. Japanese chefs sharpen their knives every day at the end of their shift. You don't need to go to such lengths. Our guidelines are:

Home cook
1x/month*
Professional chef
1x/week*


* These are rough estimates. There are several factors that influence the frequency of knife sharpening:

  • Quality/hardness of steel. The better the steel, the longer a blade will hold a sharp edge. ZDP-189 steel knives are the best knives in our offer with a hardness of 67 HRC. These will remain sharp approximately 30% longer than "regular" Japanese knives with a hardness of 61-64 HRC (like those beautiful knives made by Shigeki Tanaka, or our entry level Kuro-uchi series). German or French knives with the average hardness of 54-58 HRC will hold a sharp edge for the proportionally shorter time.
  • Usage of a knife. Fairly simple - the more you use your knife, more often it needs to be sharpened. Learning proper cutting techniques will also help. If knife manufacturer doesn't disclose steel type and its hardness, then it is very likely that steel is not the highest grade.
  • Proper maintenance. Much like any tool, regular maintenance, proper storage and correct usage will prolong the sharpness of your knives. Read the rest of this guide to learn the best ways to properly maintain your knives.

Other factors that influence the frequency of sharpening are:

  • surface/material of our cutting board,
  • type of ingredients we cut most often,
  • our cutting skills.

⚠️ Regular sharpening is a lot easier, faster and it results in less material removal compared to a knife that is sharpened only occasionally. The knife which has been sharpened regularly will prevent excessive blade wear over time. With proper maintenance, Japanese kitchen knives will last a lifetime!

Which tools do I need to sharpen my knives?

Great question. We made it easy for you and created multiple sharpening sets based on the skills of the sharpener.

Explore Sharpening Sets

⚠️  Although you can't really damage your knives when learning how to sharpen them (you can get some new scratches, but that's it), some don't feel comfortable sharpening knives on their own. If you are in this group we encourage you to seek a local sharpening service. If you are from the EU, you can use our KnifeSOS mail-in sharpening service and we'll sharpen them for you.

Some local sharpeners also offer sharpening classes to teach people the right technique. Our classes take around 3hrs and also always serve some Japanese whiskey to make the hands steady 🤣.

You are welcome to contact us for some extra advice, we'll be more than happy to help! 👍

Regular blade straightening - Honing rod!

Contrary to common belief, a honing rod or butcher’s steel is not used to sharpen the blade, but to straighten it. It straightens the tip of the blade for microscopic realignment and removal of blade deformations.

Imagine a nice, flat piece of paper. If you pass your finger over the edge of it you can cut yourself. If you crease the paper, the edge (although as thin and sharp as before) is not straight anymore and you cannot get cut. Likewise, a honing rod straightens the edge of the kitchen knife blade and therefore makes the blade straight and sharp again. Blade straightening takes roughly 10 seconds. The more frequently knives are straightened, the better it is.

Once the honing rod fails to improve blade sharpness, it is time to sharpen the knife with sharpening stones. A blade will remain sharp up to 10x longer if the honing rod is used regularly.

⚠️ There is only one thing you need to be careful when purchasing a honing rod - buying the right one for your knife. Coarse cut honing rods, or those added to cheap kitchen sets, are useless. We recommend a fine cut honing rod (made of steel) for German or French kitchen knives made of softer steel (up to 58 HRC) and diamond coated or ceramic rod for knives made of harder steel. For Japanese knives we recommend MAC's Ceramic honing rod which is fine cut and more affordable than diamond coated rods.

⚠️ Also make sure to start honing at the very heel of the blade and finish at the tip. Any other way will change the profile of the cutting edge - in time a gap will form between the blade and the cutting board, resulting in partially cut food. 

Proper Use of (Japanese) Knives

Japanese knives have delicate blades

Japanese knives are made of very hard steel (61+ HRC hardness). This allows the blade to be very thin, which ensures long-lasting, fine sharpness. That's why Japanese knives are also lighter in weight than other knives, but they are more sensitive than cheaper knives made of softer steels. Think of Japanese knives as buying a nice supercar. You won't drive your new, fancy Aston Martin off-road. Japanese knife is a high performance tool, treat it with respect.

The sensitive blade of a Japanese knife has not been designed for:

  • cutting bones 🍖
  • cheese 🧀 (due to the structure of cheese we need to apply a lot of force to cut through it, and once the blade hits the cutting board with such force, it can chip)
  • crusty bread 🥖 (especially with home-baked bread where the crust can get slightly burned. The burned part consists of mostly carbon (C), a very hard element ( 💎 - diamonds!!) that will damage the blade)
  • opening coconuts 🥥
  • and definitely not to be used as a bottle opener, screwdriver, hammer, etc. 😆 

Use of the cutting board

Never cut on a marble countertop, glass plate, ceramic baking tray, steel tray and other similar surfaces which were not designed for cutting. Use professional synthetic or wooden cutting boards. Most knife-friendly are those with the growth rings turned upwards, similar to a cut tree stump.

Another little advice when choosing a cutting board: you need at least two - one for raw meat and fish, and the other for vegetables and fruit.

Gentle use

A sharp knife cuts better, therefore you will not need much force for cutting. For certain ingredients, the weight of the blade is almost enough, others require some minimum pressure. When applying less force we damage food ingredients less, we tend to be more precise reducing the likelihood of getting cut. When the knife cuts off a piece of a food ingredient it strikes the cutting board. These strikes also influence the sharpness of the blade.

Scraping

When we cut vegetables on a cutting board we usually scrape the pieces off the board and into the pot using the blade of the kitchen knife. The sharp edge of the blade is only a few microns thick and is designed to resist vertical pressure relatively well. In case of scraping, the force is applied transversely on the board which is harmful to the blade. To scrape the vegetables off the cutting board simply turn the blade around and use the spine of the knife instead.

parts of japanese kitchen knives

Cleaning & Storage

How to clean a kitchen knife?

Regardless if your knife has been made of stainless steel or another material, regular cleaning is essential. Leaving a dirty, wet knife in the sink for a long period of time will damage the blade. This especially applies to better knives marked as 'stainless'. They are not completely stainless, they are only corrosion-resistant to a certain level. Spending a night in the sink can have sad results.

⚠️ Do not use a dishwasher for washing kitchen knives. Hot water, hot air, aggressive detergents and beating against other dishes is harmful to any kitchen knife.

We suggest to occasionally clean the knife with a cloth during use. Working with a clean knife is easier and safer, and after its use we can simply rinse it under warm water, and if necessary gently rub it with a sponge and dishwashing detergent. Then we dry it with a clean cloth and before storing it, we leave it on the kitchen counter for some time to let it dry completely. If the kitchen knife is made of steel with low or no chromium (Cr) content we can also grease it with acid-free oil (e.g. sunflower oil) before storing it.

Patina on the blade

If your knife is made of high-carbon steel, it will develop a protective layer - patina. Knives made of such steels will, due to a small percentage of chromium (Cr) in their steel structure, and a high percentage of carbon (C), develop a layer on the blade’s surface that resembles rust. However, this is not rust, but patina, a protective layer on the blade which is not a sign of defect.

For the Japanese, the superb sharpness of the blade is the sharpness that does not harm the cells whilst cutting. To achieve it, the steel has to be made of the smallest and the most homogenous grains. This fine structure allows the sharpened blade to have a fine and smooth sharpness that does not shred but cuts smoothly.

Another important factor is also the hardness of the steel (above 60 HRC) that allows for the knife to be sharpened under a small angle. All these characteristics are most typical of high-carbon steels - the ones that have a high percentage of carbon and consequently a small percentage of chromium. The latter, however, influences the knives to behave differently from the regular stainless steel knives. Therefore, with use and time, high-carbon steel blades become patinated.

⚠️ The knife is most sensitive when still new and its patina has not yet formed. When it does, it will protect the blade and make it less sensitive.

How to take care of high carbon knives?

  • Wipe your knife with a clean and dry cloth regularly, including during use
  • After use, rinse it thoroughly with lukewarm water, wipe it dry and softly oil it with knife maintenance oil. Regular refined, edible (e.g. sunflower) oil works too.
  • Store the knife wrapped in paper, as this absorbs moisture and protects the knife.

☝️ For an in-depth information about patina, read our dedicated post on patina.
 

Correct storage of kitchen knives

Kitchen knives are not supposed to be stored in drawers together with your cutlery and other kitchen utensils. Moving around and rubbing against other utensils inside the drawer will damage the delicate blade, and it is also dangerous since you can get cut while going through the drawer looking for something.

We suggest storing your knives:

  • on a wooden magnetic knife holder. You can enjoy their beautiful design even when you're not cooking,
  • in a knife sheath (Saya). You can easily store them in a drawer and Sayas will come in handy when you want to carry them around (for a picnic, cooking party, to your work (if you're a chef, haha, otherwise please don't !!)),
  • in a knife bag/roll. When you have a set of knives and you carry them around a lot.

 

☝️ This concludes our Knife Maintenance Guide. Thanks for reading it and don't forget to check our Guide on How To Choose a Kitchen Knife.

🤙 If you have any questions or need some help, get in touch. The best way is via our chat (bottom right corner) or via email (support@sharpedgeshop.com). If we are not sleeping we try to reply instantaneously 😀 .

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