Aogami vs shirogami | The difference between white and blue steel explained
When it comes to Japanese knives, everybody focuses on the type of knife and what it’s used for but there’s not much information about what steel is used during the forging process.
Japanese steel types have always been important, especially for swordsmithing.
The Japanese katana is a powerful steel blade that pierces through anything. Japanese high carbon steel is a whole other story – it’s used to make the best kitchen knives.
Blue steel and white steel are the Japanese steel types used to manufacture knives.
Aogami is the word for blue paper steel whereas shirogami refers to white paper steel. These two types of steel have different chemical compositions and carbon content but they are both types of high carbon steel. Aogami holds its edge better whereas shirogami has a sharper blade.
Most Japanese knives are made of either blue steel or white steel. So, if you’re wondering what makes your Japanese kitchen knives so special and sharp, it’s the steel.
In this guide, I’m explaining the difference between aogami and shirogami to help you make informed decisions when buying knives.
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Japanese high carbon steels
The Japanese knives are well-known because of their high carbon content.
The more carbon the steel contains, the harder and sharper the blade is. But, the metal is more brittle when it has a high carbon content.
Also, hard metals are famous for their sharp edges – they’re perfect for precise and perfect cuts through all meats and vegetables.
Aogami and shirogami steel are Japan’s high carbon metals but they’re also the hardest to forge because these carbon steels are notoriously brittle.
As a result, the blade is prone to cracking and breaking while it’s forged by artisans.
Learn more about the Japanese artisan craft of making knives here
What is aogami?
Aogami is the Japanese word for blue steel or blue paper steel and this name refers to the paper wrapping that the manufacturer uses.
Most people in the West know aogami is blue steel and it has only a small amount of impurities like phosphorous and sulfur.
But, the difference between aogami, compared to shirogami is that blue steel also contains tungsten (W) and Chromium (Cr).
These chemical elements are added because it prolongs the hardening time so the temperature is less important.
Also, W and Cr make the blade more resistant to wear and tear of daily use and the blade stays sharper longer.
Types of aogami blue steel
As I mentioned, blue steel can hold its edge much better than white steel but it’s not as sharp. Not all blue steel is the same though.
Here are the three grades of blue steel:
- Aogami #1 – has a 1.2-1.4% carbon content and hardness of 64-65. This steel is not as common as Aogami #2 but is known for excellent edge retention which actually stays sharper longer. A good example of aogami knives include the yanagiba sushi knife and deba knife.
- Aogami #2 – has a 1.0-1.2% carbon content and hardness of 62-64. It is very durable and tough steel -it’s the most durable of the 3 aogami blue steel varieties. This blade can be sharpened easily. A prime example of aogami blue steel #2 is the gyuto knife.
- Aogami Super – has 1.45% carbon content and hardness of 65-67. This steel has Vanadium (V) added to it to make it extra hard and strong. It is known for superior wear resistance. Also, this type of blue steel has the best and longest edge retention out of the three aogami steels. When crafting the blade, the added molybdenum and V gives it a long time for hardening. Thus, this steel can be cooled in oil, not just water. Some santoku knives are made of this steel.
What is shirogami?
Shirogami is called white paper steel, or simple white steel in English. It is a traditional type of Japanese steel used to manufacture kitchen knives that are very sharp.
The edge can be sharpened using Japanese whetstones (a type of natural stone).
The shirogami carbon steel contains tiny amounts of impurities in the form of phosphorous (P) and sulfur (S).
Manufacturing shirogami blades is quite challenging because it has a narrow temperature range for hardening.
Yakiire is the edge hardening process and quenching is the cooling of the metal (done in water) and both of these must be done fast to ensure the proper hardness that keeps the blade sharp.
Types of shirogami white steel
There are three forms of white steel with different carbon contents:
- Shirogami #1 – has a 1.25-1.35% carbon content and hardness of 61-64. This is the hardest type of white steel. A knife made of shirogami 1 stays sharper for longer but it is slightly brittle and may crack if used to cut through hard cartilage or bone aggressively. Some expensive high-quality Santoku knives are made of white steel #1.
- Shirogami #2 – has a 1.05-1.15% carbon content and hardness of 60-63 so it is slightly less hard. It is the most common type of white steel used for knife manufacturing. This blade will have excellent edge retention, is easy to sharpen, and is not as brittle as Shirogami 1. An example of a shirogami white steel #2 is the Japanese nakiri knife used to slice veggies.
- Shirogami #3 – has a lower carbon content of 0.8-0.9%. It is commonly referred to as yellow
- steel so technically it’s not really white paper steel. But, this blade is very durable and long-lasting just don’t expect it to hold its edge too long since it can get dull pretty fast.
Just for some perspective, VG-10 or AUS-10 steel contains approximately 1% carbon.
What is the difference between white steel and blue steel?
The main difference between these two types of high-carbon steel is the amount of carbon they contain and the hardness.
Differences between the two are hard to notice with the naked eye but you can feel different when you use them.
The general idea is that white steel blades are sharper than blue steel but the blue steel blades have better edge retention, meaning they stay sharper for longer during your kitchen cutting and food prep tasks.
Blue paper steel is very sticky and resistant to abrasion. That’s because it contains chromium and tungsten and therefore it can chip less compared to white paper steel.
White steel oxidizes faster than blue steel but overall has a much sharper edge. Blue steel is much harder than white steel and easier to sharpen because it retains its edge for longer.
During the manufacturing process and power grinding, white steel produces many more bright sparks whereas blue steel creates fewer and smaller sparks. Therefore, you can distinguish between the two according to their spark.
Is blue or white steel better?
Blue steel is known for having much better edge retention than white steel. It is also more resistant to corrosion and rust. However, white steel is better when it comes to sharpness. White steel is not as brittle and much easier to sharpen.
Did you know that aogami (blue steel) is a newer type of steel than shirogami?
But, when you ask most sushi chefs, they prefer the traditional shirogami steel knives because the blades are less brittle, sharper, and easier to use especially if you’re slicing fish, veggies, and sushi rolls.
However, I can’t say this is a universal fact because there are plenty of chefs and home cooks who enjoy the blue steel kitchen knife more because this steel delivers amazing cutting performance and better edge retention.
The problem is that blue steel is brittle and tends to chip. Therefore, you must be highly skilled to use these blades properly. Many amateurs struggle with high carbon steel knives because of the fine structure.
Japanese knives are delicate kitchen tools. You always need to make sure to properly and safely store them.
But practically speaking, you can use both knives for all the kitchen cutting, slicing, and dicing needs for Japanese cuisine.
Whether you choose an aogami or shirogami kitchen knife, you’re still making a good choice.
FAQs
Does aogami steel rust?
Yes, blue steel is a reactive material so it does rust.
Japanese blue steel is more corrosion resistant than the usual stainless steel but it virtually lacks rust-resistant properties so you can’t expect it to hold up to water.
The shirogami structure does rust when exposed to water but the key to caring for your Japanese knife is to wipe it down and make sure it’s completely dry before storing it.
The truth is that both blue steel and white steel will rust if you leave your knife in water – rust is a natural process. However, these high-quality Japanese knives have higher rust resistance.
What is super blue steel?
The super blue steel refers to Aogami Super which is no doubt one of the best types of vanadium-infused carbon steels. This steel is top-notch quality if you’re looking for super sharpness in your blade.
This kind of knife is known for its hardness. A good example of Aogami Super knives includes some Gyuto and Santoku chef’s knives.
Some paring knives used to peel vegetables are forged of super blue steel – just take a look at the Yoshihiro Aogami Super/Blue Steel Warikomi if you want to see what this blade looks like.
It is of excellent quality and is known for its razor-like sharpness.
Takeaway
Next time you’re shopping for knives, you’ll know the difference between the types of Japanese carbon steel.
White steel is best if you’re looking for outstanding sharpness and extreme cutting precision. If you’re more interested in edge retention and less frequent sharpening, the blue steel paper blade is best.
When it comes to durability, all Japanese knives are pretty good compared to the basic Western-style knives. Just keep in mind that white and blue steel knives are not as easy to sharpen so you need to get a special sharpening stone too.
But overall, the higher price tag on these Japanese knives is justified by the skill and craftsmanship required to make these carbon steels and forge the unique blades.
Carry and store your Japanese knives collection the traditional way in a Japanese knife roll
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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.
