The knife is arguably the most important tool in any sushi chef’s arsenal. It is used to slice fish into perfectly portioned pieces to top nigiri or be used in other types of rolls.
I have already written about the 3 main types of knives used in sushi making, but now I’m going to delve a little deeper into the world of steel. (For those that don’t know, steel is the metal that makes up knives). (Knives are those small sword looking things with a sharp edge and a stabby-stabby ability).
In this guide I’m going to talk about choosing the right steel for your sushi knife, as well as the difference between two main options: carbon or stainless steel.
Introduction To Steel
Steel is an alloy of iron and carbon. This is the most simple explanation, and it is why steel has been around for millennia (the oldest steel found was from 1800B.C.E.) That being said, there are many different types of steel, which can make choosing the correct one for your Japanese knife a bit of a challenge.
Modern steel was invented in 1855 by Henry Bessemer and was basically a crucible (pun intended) for the industrial revolution.
Japanese steelmaking, at least for knives specifically, aims for a balance between hardness, toughness, and corrosion resistance. Thanks to science, new and ‘better’ steels are constantly being invented by the major Japanese steel manufacturers. But let’s look at those three main traits and what they mean for Japanese knives.
Japanese Steel Traits
Hardness
Hardness in steel is like hardness in gemstones. But instead of the Mohs scale, steel uses something called the Rockwell C scale, or HRC (the C denotes steel, hard cast irons, pearlitic malleable iron, titanium, deep case-hardened steel, other materials harder than 100 HRB). The steel is tested by using a spheroconical diamond, aka a Brale indenter.
In Japanese steel a score of 60+ is acceptable for knifemaking, and is seen on all of the popular carbon steels like aogami #1 and shirogami. Stainless steel, which tends to be less hard than carbon steel, is also used in knifemaking but one should take care to buy from a quality brand as cheaper types of stainless can be too soft for long term usage.
Toughness
Toughness is the opposite of hardness and has to deal with how brittle the steel is. A very hard knife (high HRC) will tend to be more brittle thus making it easier to chip or crack.
While having a hard knife is great for professionals who use them constantly, you do have to treat them well and take good care of them because poor ownership will result in a ruined piece of metal.
Because toughness and hardness are inverses, the highest quality metal manufacturers try their best to balance these two traits.
Corrosion Resistance
Corrosion resistance has to do with how well the metal, well, resists corrosion. Corrosion is when a metal rusts due to water or salt. Various types of metal resist corrosion differently, so it is important when buying a Japanese knife to understand the best way to take care of your purchase.
An easy rule to remember is that stainless steel is almost always more corrosion resistant than carbon steel.
Is Stainless Steel Or Carbon Steel Better For A Japanese Knife
While both carbon steel and stainless steel are used to make Japanese knives, sushi masters tend to prefer those made of carbon steel. As for what is better though, that actually depends on personal preference and what your skill level is at.
Stainless Steel Pros
- Easier to sharpen
- Less expensive
- High corrosion resistance
Stainless Steel Cons
- Less hard
- Less sharp
- Less durable
Carbon Steel Pros
- Sharper
- Better edge retention
- Harder
Carbon Steel Cons
- Expensive
- Brittle
- Hard to sharpen
- Can rust*
* While carbon steel is mentioned as ‘can rust’ it should be mentioned that stainless steel can also rust or stain if not taken care of properly. Stainless steel just happens to be easier to take care of and less likely to rust.
Popular Types Of Carbon Steel Used In Japanese Knives
This part of the list will be based entirely on my experience and research, and in an order that goes from best quality to worst. I am not writing about every type of steel ever used. I am only going to mention the popular ones that you are likely to come across when searching for your own Japanese knife.
Carbon Steel
Super Aogami (Super Blue Steel)
Super aogami is considered by many to be the absolute best steel for sushi knives in the world. It is made by Hitachi Metals Ltd (which makes most of the steel on this list) and is basically a stronger, less brittle version of Aogami #1.
Super aogami is more expensive than the other carbon steels on this list. It is also much newer which means it is less readily available. The highest end blacksmiths in Japan will make gorgeous knives out of super blue steel but it does come at a cost.
Super blue steel differs from aogami #1 in that it has a higher carbon, molybdenum, and chromium percentage. It also adds about half a percent of vanadium which decreases the brittleness of the blade.
Aogami #1
Aogami #1, or blue steel #1, is arguably the most popular steel for sushi chefs. In fact, my personal takohiki is made from aogami #1 and it is one of my most treasured possessions.
Every respectable blacksmith makes high end knives out of aogami #1 so it is common to see these types of knives being used in many of the best sushi restaurants in the world.
Blue steel #1 is a very hard steel which retains its edge beautifully. Due to the brittleness factor, as well as being made from carbon steel in general, it is not recommended for beginners.
Aogami #2
Aogami #2, or blue steel #2, is almost the same as #1 but with a lower carbon content. This makes the knife slightly softer (still very hard though) and less brittle.
Shirogami #1 (White Steel)
Shirogami steels are also made by Hitachi. They are similar to the aogami line, but do not contain elements like chromium or vanadium. Due to the lack of these elements, shirogami are less hard and less brittle.
On the plus side, shirogami knives are slightly easier to sharpen so it is a good choice is you are not comfortable with your sharpening mastery yet.
Shirogami #2
Like the difference between blue steels #1 and #2, the difference between shirogami numbers is due to the carbon content. Shirogami #2 has less carbon than shirogami #1.
Shirogami #3
Shirogami #3 has less carbon content than shirogami #2.
Honorable Mention: Tamahagane (玉鋼)
Tamahagane is a steel that is quite rare to see in professional sushi chef’s knives. It is the steel of choice for swordsmiths and is one of the more ‘historical’ Japanese steels available.
In my opinion, tamahagane knives do not have any superior ability compared to aogami/super aogami. I see them more as an art and the knives made from this steel are for display or high-end gifts.
Stainless Steel
VG-10
Made by Takefu Steel Company, VG-10 is the most popular choice for stainless steel sushi knives. What it lacks in hardness compared to carbon steels it makes up for in toughness and corrosion resistant abilities.
VG-10 knives range from affordable to expensive, so there is something for everyone. In fact, my gyuto (pictured at the top of this article) is a VG-10 knife from Togiharu (house brand of famous Kappabashi shop Kamata-Hakensha).
VG-1
Think of VG-1 as the precursor to the more popular VG-10. It is a similar steel as it’s successor but it does not have the addition of vanadium for hardness.
VG-1 steel knives are great for beginners as they are more affordable and easy to maintain.
Gin #3 (Silver #3)
One of my personal favorite steels for sushi knives is ginsan #3, aka silver #3. This steel was developed to be a balance between the hard but brittle carbon steels and the easy to sharpen, corrosion resistant stainless steels.
Silver #3 is a metal made by Hitachi (which makes the best carbons steels) so you know you are getting quality when you purchase a ginsanko knife.
Swedish Steel (AEB-H steel)
Believe it or not, Sweden is known even in Japan as producing very high quality steel for knife making. The company Uddeholm makes a steel called AEB-H which is loved by certain Japanese blacksmiths.
Swedish steel can achieve a very high hardness, while retaining it’s anti-corrosion abilities, making this a great option for those just starting out. That being said, I personally have no experience in using or maintaining a Swedish steel blade so my opinion may not mean much.
Powdered Metallurgy (PM Steel)
Powdered metallurgy is a modern method of steel production that can achieve extreme hardness without sacrificing toughness. It is made by sintering (fusing by high pressure) fine particles into an alloy that has a near perfect chemical structure.
Due to the newness and expense of this method, knives made from PM steel can be very expensive. Most of the famous Japanese knifemakers do not make knives from PM steel, but for those that do they can achieve high sales prices from connoisseurs.
PM Steel can be made into both stainless and non-stainless knives so it is important to know what you are buying before you pick up a PM steel knife.
Two premium lines of PM steel include the ZDP189 (stainless) and the HAP-40 (semi-stainless) which are both made by Hitachi.
So…What Should I Choose For My Sushi Knife
As mentioned up above, the choice is entirely up to you. You need to choose what you prefer in a knife and for your purposes. There is no such thing as a ‘perfect knife metal’, only things that suit certain needs.
Most sushi chefs use blue or white steel as their choice, as I do for my takohiki (a type of sashimi knife), but if you are just looking for an easy and convenient everyday knife then a stainless steel gyuto (chef’s knife) might be more applicable.