What is a black knife? Does it peel? A thorough explanation of the differences and benefits between traditional "black" and "modern coating"

"I want a cool knife that's different from others." "I want to use a black, sophisticated knife like the ones used by professionals."

So, if you're researching "black knives," did you know that there are actually two completely different types of black knives?

One is the traditional "Kurouchi" crafted by Japanese blacksmiths. The other is the modern "Black Coating" that uses the latest technology to enhance functionality. Although they both look black, the contents and characteristics are completely different.

In this article, we will explain in detail the "true nature of black knives" that you should know in order to avoid making a mistake when choosing a knife, and their benefits that are recognized by professionals.

What is a black knife? The difference between "traditional black forging" and "modern black coating"

Products known as "black knives" are broadly divided into two schools, depending on whether the black color is "natural" or "artificially processed." Understanding this difference is the first step in finding the one that's right for you.

[Traditional] Kurouchi: A rugged aesthetic with the oxide film left from the quenching process.

Knives known as "Kurouchi" are made using a traditional Japanese method, most famous for being made by Tosauchi blades from Kochi Prefecture.

When making knives, there is a process called "quenching" in which steel is heated to a high temperature and then rapidly cooled in water. During this process, the surface of the iron oxidizes at high temperatures and becomes covered with a blackish film.

With a typical silver knife (polished knife), this black film is polished off at the end, but "Kurouchi" knives are those that are deliberately left as they are, rather than removing the black film.

The surface is rough and has an uneven texture that tells of the intensity of the hardening process. No two pieces are the same, and they have the charm of being like "rugged craftsmen's tools."

[Modern] Black finish (black dyeing/fluorine): An evolutionary step forward in design and rust prevention

Meanwhile, modern black knives made using the latest technology have been gaining popularity in recent years. These are produced by many manufacturers, including Sakai Cutlery (Osaka Prefecture) and Seki (Gifu Prefecture).

Stainless steel and steel are given a black finish through the following artificial processes.

• Fluorine coating (Teflon) : A method of covering the surface with resin, like a frying pan. It has a matte, uniform black finish, is highly resistant to rust, and is easy to clean (e.g., Sakai Takayuki's "Kurokage").
• Black dyeing (oxidation coloring) : A method in which stainless steel or steel is immersed in a special liquid to cause a chemical reaction, resulting in the formation of a black oxide film. Unlike coatings, this method discolors the texture of the metal itself, resulting in a luxurious finish.

Why is it black? The crucial difference between "benign rust" and "painted"

The crucial difference between these two is the true nature of the color black.

■Traditional (black finish) is "oxide film"

This is a type of "burnt" or "rust." It is a natural film formed when the iron is burned, and is not a paint. Therefore, its distinctive feature is that you can enjoy watching it "develop" as it gradually fades and the scenery (pattern) changes over time.

■Modern (coating) is "film"

This is a barrier that protects the surface of metal. It is applied for functionality and design purposes, and is characterized by its ability to maintain a uniform, beautiful appearance for a long time (although it will wear down with use).

Three benefits of choosing black knives

Many people pick up black knives because they look cool, but in fact they also have many logical functional benefits. There is a clear reason why professional chefs and fish market workers love black knives.

1. Rust resistant: "Black rust" acts as a natural coating to protect the iron

The greatest benefit of the traditional "kurouchi" finish is its rust prevention effect. There are two main types of rust that occur on iron.

• Red rust: The so-called "bad rust" that corrodes iron.
• Black rust: "Good rust" that adheres to the surface of iron without any gaps, protecting the interior.

The black part of a black-finished knife is this "benign black rust (oxide film)." This film prevents oxygen and moisture from coming into direct contact with the iron, preventing the formation of its enemy, "red rust."

People tend to think that steel knives are difficult to care for because they rust easily, but if you take good care of the moisture on the edge of the blade (the silver part that actually cuts food), the entire blade rarely rusts and is actually surprisingly easy to use.

Of course, modern coatings such as fluorine provide even stronger moisture protection, making them even more rust-resistant than stainless steel knives.

2. Best value for money: By eliminating the polishing process, you can get "cheap, high-quality steel."

This is mainly an advantage of traditional (black) knives, but black knives are said to have the "best cost performance."

To make a regular silver knife, it takes time and money to polish the surface that has turned black during quenching until it shines brightly. However, Kurouchi knife deliberately omits this "polishing" process. In other words, it cuts out unnecessary costs for appearance processing.

To compensate for this, the steel inside is often made from the highest quality materials such as "Aogami" or "Shirogami," which means that "for knives with the same sharpness, Kurouchi knives are overwhelmingly cheaper." For professionals who value practicality and those who want to get good tools at a low price, there is no more rational choice.

3. Food doesn't stick easily: Practicality thanks to the uneven surface (matt finish)

What surprises you when using a black knife is how easily ingredients separate from the cut pieces.

• For traditional knives : The roughness and unevenness of the oxide film remaining on the surface (pear-skin texture) creates a layer of air between the food and the blade, preventing thinly sliced ​​cucumber or radish from sticking to the blade.
• For the modern type : Fluorine coatings and similar have a very low coefficient of friction, allowing food to be cut smoothly.

I was initially drawn to black knives because of their cool appearance, but they are actually highly functional tools that can help relieve the stress of cooking, as they are rust-resistant, sharp, and food does not stick to them.

[Things to note before purchasing] Will the black color come off when sharpened? The truth about discoloration

Before purchasing a black knife, there is a "truth" that you should be aware of. It is about the complaints you often see online, such as "The black paint started to peel off after use." This is not a defective product, but rather an unavoidable fate due to the structure of the black knife.

Understanding the structure: "The black is only on the surface" - sharpening will always reveal the silver base metal

First of all, it's important to understand that, with the exception of ceramic knives, black metal knives are not black all the way through. Whether it's the traditional "kurouchi" or the modern "coating," only a layer of blackened surface is used, and the inside is the same "silver-colored steel or stainless steel" as a regular knife.

Therefore, when the knife loses its sharpness and is sharpened with a whetstone, the black coating on the sharpened part (the cutting edge) is scraped off, and naturally the silver base metal appears. If you buy it hoping that it will stay jet black forever, you will be shocked when the silver color appears and realize, "The paint has peeled off! It's gotten dirty!"

This is not deterioration! Once the silver blade pattern appears, the real "development" begins.

However, for knife lovers, this change is not a deterioration but an "evolution" and "development."

While a brand new, jet-black knife is beautiful, professionals believe that the appearance of a sharp silver line (cutting edge) on the cutting edge after use is what truly represents "functional beauty as a tool." The black body and the finely honed silver blade are a testament to the seriousness with which you have taken your cooking and maintained your knife.

Instead of lamenting that the color has worn off, think positively and say, "The blade pattern has appeared, and the knife has grown into something uniquely yours." This is the secret to enjoying your black knife for a long time.

The "Kobatsuke" option for those who want to maintain the black color

"I understand the logic, but I don't want to reduce the black area because I care about appearance." If you think like this, we recommend that you try a creative way to sharpen the knife.

Instead of sharpening the entire cutting edge like a professional, we sharpen only the tip of the blade, about 1 mm at a slight angle, using a method called "kobazuke." This minimizes the amount of silver that turns silver, maintaining the "pitch black" appearance at first glance.

Another option is to use a simple sharpener instead of a whetstone. The sharpener is designed to sharpen only the tip, so you can restore sharpness without damaging the black part on the side (however, maintenance with a whetstone will be necessary over the long term).

Which black knife is best for you? Type-specific diagnosis

As we've explained so far, each black knife has its own unique characteristics. Choose the type that best suits your cooking style and personality.

If you value ease of care and design, choose "Fluorine/Teflon Coating"

Recommended for:

• I'm busy and it's a hassle to take care of it in detail.
• I absolutely hate it getting rusty.
• I want to unify my kitchen in a stylish way.
• I want something that doesn't stick to food.

This type of knife has a stainless steel surface that is treated with a fluororesin coating, similar to that of a frying pan. Its greatest feature is its overwhelming ease of use. It repels water, making it extremely rust-resistant, and dirt comes off easily.

It has excellent cutting ability and glides food smoothly. If you are looking for modern convenience over tradition, Sakai Takayuki's Kurokage series is a good choice.

For authentic sharpness and the joy of developing your own blade, choose "Tosa-uchi Blades - Traditional Black Blade"

Recommended for:

• I aspire to have the sharpness of a professional knife.
• I want a knife that is cost-effective and made of good quality steel (blue paper or white paper).
• I like the rugged, rough, artisan-made feel.
• I want to sharpen my tools myself using a whetstone and develop them.

This is a traditional type that leaves the oxide film that was created by hammering and forging the iron intact. It looks rough and rugged, like it has dirt on it, but inside it is often made of the highest quality steel, and it has excellent sharpness. Another attractive feature is that it is reasonably priced despite its high performance, as the polishing process is omitted. There are many masterpieces among the products of Kochi Prefecture (Tosa).

If you want to satisfy your overwhelming desire to own it, choose "Special Black Dye Damascus"

Recommended for:

• I want to have a special one that is different from others.
• We place more importance on visual impact and beauty than price.
• I like the katana-like feel.

This high-end model is made from stainless steel or Damascus steel that has been dyed black using a special chemical reaction. It does not have the feel of a coating like fluorine, and the black coloring retains the natural luster of the metal, giving it a captivating, luxurious shine.

Golden rules for maintaining and cleaning black knives to avoid mistakes

To keep your favorite black knife beautiful and useful for a long time, you need to know some "taboos" that are a little different from those for regular knives. In particular, you need to be careful not to wash it incorrectly, as the black color may peel off on the first day you buy it.

[Absolutely no-no] Metal scrubbing brushes and abrasive sponges cause black peeling

The most common mistake is scrubbing with a metal scouring pad or the hard part on the back of a sponge (abrasive non-woven fabric) when trying to remove dirt.

If you do this, neither traditional oxide coatings nor strong fluorine coatings will stand a chance. The black coating will be scraped off in an instant, leaving the knife with a scratched silver finish. When cleaning a black knife, always use a soft sponge. Even if the stains are difficult to remove, soak it in warm water to soften it, and never try to scrape it off with physical force.

Regular care: Be gentle on the black parts and thoroughly moisturize the blade edge

The trick to maintaining a black knife is to vary the maintenance depending on the area.

• Black parts (sides): These have an anti-rust coating, so there's no need to worry. Just wash them gently with detergent and a soft sponge.
• Silver part (edge) : This is where the iron or stainless steel is exposed. Especially in the case of the traditional "kurouchi" style, rust will start to form from this edge. After washing, immediately wipe off any water with a dry cloth. By doing this carefully, you can prevent rust problems.

[Trick] How to protect the pattern with masking tape to prevent it from getting dirty

This is a professional technique that anyone who sharpens their own knives using whetstones should know.

When sharpening a black knife, the water on the whetstone mixes with the black sharpening juice to produce a jet-black sharpening fluid. If this soaks into the wooden handle, it will turn black and look very unattractive. Therefore, before sharpening, wrap masking tape around the base of the handle to protect it. This will prevent the sharpening juice from seeping in, and keep the handle clean and beautiful forever.

Frequently Asked Questions (FAQ) about Kuroknives

Q. Is it safe if the black coating or oxide film peels off and gets in your mouth?

A. Basically, there is no harm to your health.

The black film of traditional "Kurouchi" is iron oxide (iron rust), so even if a small amount enters the body, it is harmless and is simply absorbed and excreted as iron.

Furthermore, even if modern "fluorine coating" comes off and enters the mouth, it is an inactive substance that is not absorbed by the body and is simply excreted. As the material used complies with the Food Sanitation Act, there is no need to worry excessively.

Q. Will the black color come off if I wash it in the dishwasher?

A. We do not recommend using a dishwasher.

Dishwasher detergent is highly alkaline and can deteriorate the coating and damage the oxide film on the black finish. Also, washing with hot water at high temperatures increases the risk of drying out and cracking the wooden handle.

We generally recommend hand washing, except for all black stainless steel knives that are clearly labeled "dishwasher safe."

Q. If red rust appears, what should I do?

A. It removes only the rusted parts with pinpoint accuracy.

If red rust appears on the edge of the blade (silver part), it can be quickly cleaned by re-sharpening it with a whetstone.

If red rust appears on the black parts, gently rub off only the red rust using rust remover rubber (Sabitol) or a wine cork with cleanser on it. If you rub too hard, you will remove the black film as well, so proceed carefully and keep an eye on the condition.

Summary: Sharpen and develop your black knife to become a lifelong companion

Black knives are not just tools that look cool.

• The traditional "Kurouchi" knife is a practical tool that is inexpensive, has a sharp edge, and the black rust protects the body.
• The modern "black coating" minimizes the effort required for maintenance and makes it a modern tool with the ultimate design.

Whichever you choose, the process of the blade becoming sharper with use and the contrast between black and silver emerging will be an irresistible joy for any culinary enthusiast. It will look even better a year or five years from now than when it was new. Why not give a black knife the "fun of growing" and make it your kitchen companion?