Why can Japanese knives chip?

To make a knife as sharp as Japanese chef knives there are a couple of things you should know about how they're made and how to use and look after them to avoid any accidents.

If you've bought a Japanese blade then we assume you like sharp knives but in order to get the best life out of them you need to remember you can't treat them like their beefier western counterparts. Some slight adjustment of cutting technique is needed so you can enjoy a long and happy life together in the kitchen.

"The knife chipped, it's faulty"

Nearly every time, a chip is an accident. Faulty steel fails in a very easy to identify and clear way so chips are almost the result of an unfortunate accident of some sort. 

It might be hitting a bone or even a slight twist while cutting that stresses the blade in a particular way that one time. Once a customer has used a knife in their kitchen, it's impossible for us to know how they cut, what it's been used for so there's simply no way to advise on what might have happened to cause a chip.

If you have chipped your knife - don't worry! We've not seen a chip that can't be fixed somehow. It's simply an unfortunate accident in the same way as scuffing the alloys on your Ferrari might be if you catch it on the edge of a pavement while driving.

What might cause chipping?

Japanese knives are made differently to Western knives. To achieve great sharpness some compromises need to be made but we think it is worth it.

Much thinner blades

A Japanese blade is typically much thinner than a Western one. The spine of the knife (the top part of the blade) may appear about the same width but the cutting edge is much thinner. This thinness allows the knife to cut better, it's pushing/dragging less through the ingredient.

Pro: A thinner cutting edge means it is less of a wedge that you have to drag through the food so it cuts much better.

Con: The thinner cutting edge means you have to be more precise with your cutting action than with a Western knife and take more care to cut straight and avoid twisting.

Sharpened to a higher angle

Western knives are typically sharpened to 20-22 degrees on each side. The Japanese knives we sell are typically 15-16 degrees on each side. This might not sound like much of a difference but it makes a massive impact in just how sharp that knife feels.

A knife is a sharp wedge at the end of the day and the wider the wedge the more effort required to push the knife through the ingredient. So our knives are smaller wedges which is why they cut through things easier.

Pro: The lower edge angle allows the blade to cut through the food easier.

Con: A lower edge angle means a sharper edge that you need to refine your cutting style to get the most benefit from.

Hardened to a very high level

Steel can be hardened to all sorts of levels. This is referred to as the Rockwell Hardness of the steel. Western knives are typically 55-58 on the scale. The Japanese knives we stock are typically 62-65 on the scale.

Again this might not sound like much of a difference but it is. The edge of a western knife will bend when damaged, a Japanese one will chip. The reason for the increased hardness is due to Japanese knives being sharpened to a higher angle. The edge would soon become blunt as the softer edge would roll over.

To explain this better try this; hold your hand in front of you as if you are going to do a 'karate chop'. Your finger nails are the cutting edge. Now curl your fingers over a little, this is what a softer steel with do if sharpened too thinly, it will curl or roll over. Your knuckles are now your cutting edge, not all that great is it? The hardness is increased to counter that and allow the knife to hold a sharper edge for longer. The draw back is rather than curling, the blade can chip (imagine cutting off one of your fingers in your 'karate chop' knife).

Pro: Higher rated hardened knives retain their edge much longer than softer steel.

Con: Higher rated hardening can make the steel more brittle (this is why soft lead bends and hard glass shatters).

So we are trading off rugged handling for a sharper knife. Think of it as driving a sports car, capable of amazing speed and cornering but rubbish at driving through fields and pot holes.

How to reduce the likelihood of chips

You won't like this bit - but if a knife chips then it is mostly likely down to you and how you handled it. You have to adjust the way you use it.

It's not a western knife so you can’t go swinging it around and expecting it to cut through bones, trees or chopping boards. But remember that it cuts better than any knife you’ve used so the refinement in your style will be worth it.

The basics.

Cutting is all that a Japanese knife is for (as a bonus they tend to look damn good too).

Not wiggling the thigh joint apart on your Sunday roast chicken, not opening tins, not opening packaging, not separating frozen pork chops or cutting through bones (unless it’s a meaty blade like a Bunka or Deba) keep your old knife around for those sort of tasks if necessary.

You can’t use it on a plate, glass chopping board or metal roasting tin - these are all harder or chunkier than the thin steel on your knife edge and something will have to give. As the blade can't bend easily it could at best go blunt and at worst chip.

Don’t bash the edge around, this means putting the knife down on the work top not throwing it, not putting it on your sink draining board awaiting a pan to be put on it or letting it rattle against the sides of the sink while you wash it. Wash it separately, wipe it and store it somewhere safe where nothing else can bash against it.

Never put it in the dish washer, but you knew that.

Avoid "the bang"!

We've started calling this the "butternut squash problem". Some veg takes some oomph to get through it, those ones you have to put your hand on the spine of the knife and then bear some weight down on it. Avoid this if you can. It's not cutting, this is splitting really so use your other knives for this sort of offroading.

What can happen is when the veg eventually (or hopefully) gives from your efforts it splits in half and the knife "bangs" into the chopping board with as much force as you applied in an instant. The outcome of this shock can be a chipped knife. Annoyingly you might not notice it at first until you are chopping something softer and now we don't know what happened...chances are...it was "the bang".

We've seen this reported with anything super hard or dense such as sweet potatoes, swede, turnips and of course butter nut squashes et al, even hard cheese can do this if you're not paying attention...too much port? Again, this is not cutting/slicing you're just using lots of force to split the veg in half and ramming the knife into the chopping board.  

Twisting and shearing

As the blades are thinner and made of harder materials they really don’t like sideways or twisting forces. These are probably the number 1 reason for a chip when in use. If you scoop up your veg from your chopping board with the knife for instance (something the Nakiri is designed for with its extra wide blade) you should move the veg onto the knife not the knife under the veg. Otherwise it is possible to have a part of the blade dig into your board and twist and then possibly chip. As a bonus dragging the knife over the board like this will make it dull quicker too so another reason to avoid doing that with any knife.

Avoid sideways forces and keep that super sharp edge.

Magnetic racks

The metal on some magnetic racks can chip a blade, the magnet can pull the knife hard onto the metal strip and if the edge hits first it’s possible to chip it. This is why we only sell wooden knife racks. The wood gives rather than the steel on your blade and saves any chipping.

So should I treat them like they are made of glass?

No of course not! You should use them as intended and enjoy every chop, dice and slice. Pretty as they are they are not art to be hung on their wall. They are tools to be used but you have to use the right tool for the right job and in the right way.

Every tool has a use it was designed for, our job is to know that use and work within the limits of its design.

Our knives cut really well, stick to using them for cutting and you should have a chip free time with your knife while experiencing the joy of cooking with a sharp knife for a long time.