How to sharpen a Japanese knife | Use a whetstone, step-by-step

by Joost Nusselder | Updated:  January 15, 2022

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Do you own all kinds of Japanese knives but worry about the costs of getting them sharpened professionally?

No matter if you are an expert cook or just like preparing something fast, you must sharpen your knife so you can cut the foods easily and avoid sloppy cuts.

There are several reasons to sharpen your knife but the main purpose is to increase cooking efficiency and to reduce preparation time.

How to sharpen a Japanese knife | Use a whetstone, step-by-step

You might’ve seen sushi chefs sharpening their knives before they prepare the rolls or sashimi or at the end of the long workday. That’s because you can’t be efficient and make clean cuts with a dull knife.

Japanese knives generally require more frequent sharpening than the average Western ones.

In Japan, they don’t use an electric knife sharpener but a special knife sharpening stone called a whetstone or water stone.

If you want to sharpen your own Japanese knife, you can do it at home with a whetstone. When preparing fine cuisine using Japanese knives, part of maintaining the knife in good shape requires frequent sharpening while it’s still pretty sharp.

After all, having a razor-sharp blade is the key to efficient chopping and cutting.

I’m sharing the top Japanese knife sharpening tips so you can always have a sharp knife on hand ready for any difficult food prep task.

Can Japanese knives be sharpened?

A Japanese chef doesn’t start cooking before making sure that the knife is super sharp. In fact, sharpening the knives is the first step to preparing delicious Japanese cuisine.

Sharpening Japanese knives can be a challenge but the good news is that you can sharpen your knife at home using a whetstone in about five to ten minutes.

It’s best to sharpen the knife before it gets dull. This way, you can do the sharpening at home in approximately 5 to 10 minutes by grinding with the whetstone.

What angle should a knife be sharpened at?

For most Japanese knives, the answer is 17 to 22-degree angles.

Most knife makers in Japan pre-sharpen the knife at about 17 degrees for the consumer using their whetstone knife sharpeners.

Since most traditional Japanese knives are single-bevel, it means that the side of the blade is sharpened to between 17-22 degrees.

For this answer, I have to generalize a bit and talk about the Gyuto and Western chef’s knife because it’s the most common type of traditional Japanese knife people own.

During the sharpening process, aim for an angle that gives a razor-sharp, effortless cutting edge as well as a long-lasting angle that won’t dull after each usage.

So, what’s the ideal vantage point? When making food, sharpen your knives at a 15 to 20-degree angle for the greatest results.

This offers a sharp edge that will make cutting easy. The edge won’t be dull and you can have peace of mind.

Why are Japanese knives sharpened on one side?

Most of the popular Japanese knives have a single bevel blade, so you only need to sharpen one side.

The fact that these knives are only honed on one side makes them sharper since you can create a smaller and sharper angle.

The sharp angle is excellent for precise slicing, cutting, and dicing. For many popular Japanese dishes like sushi, precision is key.

Best way to sharpen Japanese knife: whetstone

Best way to sharpen Japanese knife- whetstone

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Use a whetstone when sharpening a Japanese knife. The sharpening process takes longer but gives amazing results and a super sharp edge.

Technically, any type of sharpening stone can be called a whetstone no matter the cutting fluid that is generally used with it.

Whetstones come in a variety of shapes and sizes, including water stones, oil stones, diamond stones, and ceramic stones.

Whetstones are water stones, although not all water stones are whetstones. Whetstones are the ones you can use to sharpen your Japanese knife.

Sharpening a stone works in a similar way to sanding wood. The whetstone removes material from the edge of the blade to shape and polish it into an acute blade.

Kota Japan offers great whetstones, check it out here.

How to sharpen a Japanese knife with a stone

Sharpening using whetstones is an ideal method for keeping knives shiny and providing smooth, sharp edges.

The whetstones are rectangular pieces of stone used for cutting knives.

Although using whetstones may take a little practice according to expert advice, using whetstones can help maintain good quality knives.

When you sharpen a Japanese knife with a water stone, it’s important to take a personal approach and sharpen it for your specific needs.

The sushi chef sharpens his precious knife every day and it comes down to two things: the blade edge life vs easy sharpening.

The choice is yours to make this decision based on your own needs and preferences.

It’s worth choosing a knife to suit your skills as a sharpener and meet your needs. For someone with no prior experience with Japanese knives or waterstones, use the easiest knife for sharpening.

When you work your knife with stones, your knife begins personalizing the edges to your specific needs and sharpening style.

With practice and proper skill, your knife will sharpen up quicker and sharper.

What is the proper sharpening method?

First, you must learn how to look at the blade. Does it look sharp enough?

Does it contain nicking or anything else? How do I diagnose my edges?

You may adjust the angle ratios of your knife when balancing the blade.

For example, you could sharpen a double edge knife rated 50/50 to 60/40 or 70/30 to get something that resembles a Japanese knife.

The final tip is to keep it flat: When the stones are concave, they’ll have difficulty controlling the sharp blades arching in.

Also, people often underestimate the need to fix the surface on stones. Make sure that it is solid because the stone shouldn’t move when sharpened.

Step one

The first step of sharpening is the preparation of your stone.

First, splash or soak the medium or rough grit whetstone with water for 10 minutes or so. For fine whetstones only spray it with some water using a spray bottle while you’re sharpening.

Step two

Place the rock into something solid and keep it steady when the sharpener reaches a point. Some whetstones have holders which can easily be put in an easily damp tea towel on a table.

If not, grab a wet close or nonstick base and place the stone on it to stabilize it while you sharpen the knives. The experts recommend getting a larger stone base on which to place the whetstone.

This keeps it safe and sturdy in place and it also gives you plenty of knuckle clearance so you can sharpen safely and efficiently.

Lifting the water stone from the tabletop ensures that you have a better angle that’s easier to work with.

Step three

You need to hold the knife by having the index finger rest on the spine of the knife. The thumb must be on the flat part and your other three fingers should grasp the handle firmly.

Start sharpening by doing the knife tip first. Use two or three fingers on your left hand and press down the blade’s edge on the stone.

Hold the knife with your index finger resting on the spine and thumb on the flat of the blade, while the three remaining fingers grasp the handle.

Step four

For maximum efficiency, you want to make sure your upper body is in a relaxed position.

Then, while pressing the blade’s edge along with the stone, you need to exert pressure as you move forward and release the pressure when you pull back towards the start position.

Glide the blade on the stone for about 10 minutes. Yes, I know it is tiring but you need to do this if you want super sharp knives.

Step five

Now you need to keep repeating the previous step while closely pressing the blade’s edge to the stone.

You need to sharpen bit by bit one small part of the edge at a time. You’ll feel the even burr across the whole edge.

After the burr is formed, it’s time to reverse the blade and begin sharpening the tip if you have a double-sided blade (double-bevel).

At this point, it’s okay if you apply more pressure on the downward stroke. You’ll either get rid of the burr or create a sharp double-bevel blade.

It’s easier if you watch an instructional video:

Japanese vs Western knives

Japanese-style knives are usually single bevel.

For deba knife, yanagiba, takobiki, usuba, and the kamagata usuba you want to sharpen the whole cutting edge and make sure you get an even burr on the other side.

It sounds tricky but you need to place your blade in a perpendicular position to the stone and make sure it lays completely flat.

Then, with your index and middle fingers, remove the burr by pressing the edge gently to the stone. The thumb needs to press on the knife’s spine gently.

When you press down both sides of your blade, it maintains the concave shape of the reverse blade.

This allows you to keep sharpening the knife over and over again without losing its shape. The motion resembles water getting pushed off the stone.

Now flip your blade over and work on sharpening the shinogi line. This shinogi line refers to that part where the cutting area tapers down towards the edge.

This line influences how smoothly the blade moves through meat and other food. So, you’re not allowed to erase the shinogi line while sharpening or you ruin the blade.

To sharpen the shinogi line, press down just below the middle part of the blade and move the fingers away from the blade’s edge.

When sharpening Western-style knives, you need to know to angle to stone ratios as well as the type of bevel you have.

You have to angle each knife to best determine the cutting edge: most experts recommend a 10-20 degree angle.

These Western knives aren’t designed to be as sharp as Japanese ones so if you sharpen to a smaller angle, you risk weakening the cutting edge.

It’s best to use the same angle consistently until you learn how to sharpen properly. With two pennies, you can create that 12-degree angle more easily.

Did you know the Japanese can also cook a Western pasta? It’s called wafu pasta and here’s a great recipe to try

How often do you sharpen a Japanese knife?

Ideally, a sharpened knife is a must when cooking.

Japanese traditional knives are known for their super sharp and strong blade edges – this sharpness sets them apart from your basic Western knives.

Japanese knife manufacturers provide initial sharpening for exceptional clarity and precision when you take it out of the box.

However, the knives lose their sharpness after a few uses so you need to re-sharpen them especially if you’re cutting delicate ingredients like raw fish for sushi.

Experts recommend that you sharpen a knife often to prevent it from getting dull. Sharpening the dull knife takes much longer.

You can evaluate the sharpness and condition of the blade using simple paper tests.

The blade has to slice paper without getting caught and must cut the edges without tearing unevenly. If the edge catches the paper at all, there’s a dull part on the blade.

For your convenience and safety, these dull or uneven edges need to be sharpened ASAP before you start cutting.

As a regular home cook, you can get away with sharpening your Japanese knife just once or twice per year. If you use it more frequently, you’ll probably need to sharpen it at least once every couple of months.

Those who use the knife often should hone it after each use to ensure the edge stays sharp for longer.

How to take care of your whetstones?

Because stones are delicate, they should never be over-soaked.

Soaking the stone too long will degrade its quality and make honing more difficult.

After sharpening, wipe clean and allow to air dry. Storing stones in a dry towel is recommended.

Returning a moist stone to its cardboard box might cause mold to grow, weakening the stone and causing fracture or separation, not to mention that mold is gross and unsafe.

The first step to take is to make sure you lay the stone flat before sharpening. Note that after frequent use, ceramic and synthetic whetstones start to wear down.

Therefore, you need an authentic Japanese stone fixer that flattens the sharpening stone’s surface.

If you use a concaved stone, it loses its shape and warps which then ruins and changes your blade’s shape.

You need to soak the stones properly depending on the type.

The medium grit and rough grit whetstones must soak in the water for about 10 to 15 minutes before you use them to sharpen knives.

You’re not supposed to soak fine stones in water because they can crack. For fine stones, you need to spray a bit of water on the whetstone at the same time that you sharpen.

If you own a double-sided whetstone with a fine and medium grit combo, only soak the medium side in the water.

Sharpening Japanese carbon steel knives

You sharpen carbon steel knives the same way you sharpen the others using a whetstone.

First, you soak the whetstone to make sure it works well.

Usually, you can sharpen chef’s knives (gyuto knives) at a 15-degree angle. If you place two quarters on the stone you can approximate the 15 degrees.

Then, while the blade edge is towards you, start to push the knife away maintaining the 15-degree angle.

Don’t apply too much pressure – keep it firm but still relatively light and repeat this motion over and over again.

As soon as you can feel that curled metal of the edge it’s time to flip your knife over.

FAQs

There are still some unanswered questions you want to be answered so here they are:

Can you sharpen a Japanese knife with steel?

Any single bevel Japanese knife can never be sharpened with steel because steel ruins the blade.

The general rule is that a Kataba blade cannot be sharpened with steel, only with a whetstone. The single beveled deba knife, usuba square knife, or the yanagiba sushi knife are damaged by steel.

Knives with a 50/50 bevel like the chef knife can be sharpened using steel if you’re tight on time.

Using a simple steel sharpener is quite easy and effective with such a knife and you don’t need the same skills that you need when using a water stone.

So, for a rapid tune-up, you can get away with using honing steels.

If you use a honing steel, it won’t have the same effect as a professional sharpening whetstone.

It cannot reshape the bevel to the same precise acuteness but it can take off some of the metal and:

“re-align the microscopic burr to a straight line, increasing cutting ability for a while” (Chef’s Armoury)

Types of honing steels

There are 3 main types of honing steels:

  • ceramic steel: the ceramic honing steel is ideal for sharpening Japanese knives. It needs to be of good quality and sturdy so you can apply even pressure for precise angled sharpening.
  • diamond steel: this isn’t the best type of honing steel for Japanese knives because they end up removing too much metal from the blade and it’s hard to apply even pressure so you might end up with misshapen blades
  • stainless steel: this blade can be a bit too coarse for delicate Japanese blades but if it has super smooth teeth it can work

How to sharpen serrated knives?

You will need a sharpening machine that is compatible with serrated knives to sharpen them.

The SHARPAL electric knife sharpener works well for serrated knives and it’s much easier to use than manually sharpening those tiny grooves.

Here’s the thing though: Japanese knives aren’t traditionally serrated.

These days you may find some bread cutting serrated knives or some European chef’s knives and for those, you can use an electric sharpener.

While sharpeners have been developed for sharpening sharp objects, we found the devices frustrating. The electric sharpener only sharpens its edges and tips of serration and not its valley between the edges.

Don’t panic though, it’s not necessary to send the knife to a professional. A manual sharpener can ride through the different segments (pointed scallops or saw-toothed) while sharpening both sides and tip.

The sharp edges can be sharpened much less often than the smooth blades because they are pointed, but they have less friction at their ends.

Japanese bread is delish, here’s the secret to why it’s so soft and milky explained

Is it possible to over-sharpen your knives?

It’s just not true. Do not believe common sharpener myths.

Truth: The correct electric sharpener can help prevent heavy metal loss.

Electric sharpeners can remove metals when you griddle the knives—even when you use coarse grinding to sharpen an especially dull knife.

Some electric sharpeners have 3 different sharpening options. The fine slots are the most often used for polishing bare blades.

Takeaway

When you’re on a mission to sharpen your knife, the classic Japanese whetstone is still the number one option. You can get one with a fine, medium, or rough grit, depending on the type of knife you want to sharpen.

Luckily, sharpening a Japanese knife at home is possible but don’t use those electric sharpeners people use to sharpen Western-style knives.

The advantage of a whetstone is that your knife will maintain a sharp edge for longer.

Just be sure to store the knives properly after sharpening and maintain your blades by honing them every once in a while.

Read next: How do you say “thank you for the food” in Japanese?

Check out our new cookbook

Bitemybun's family recipes with complete meal planner and recipe guide.

Try it out for free with Kindle Unlimited:

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Joost Nusselder, the founder of Bite My Bun is a content marketer, dad and loves trying out new food with Japanese food at the heart of his passion, and together with his team he's been creating in-depth blog articles since 2016 to help loyal readers with recipes and cooking tips.