Knives with black blades are chosen not only for their looks but for practical reasons, too: food releases more easily and rust is less noticeable. But “black knife” covers several different things. There is more than one reason a blade can be black, and each type needs slightly different care. On this page, Hayashi Hardware (founded in 1872) explains the types of black knives and their characteristics, what the wavy hammered pattern (tsuchime) is for, and how to look after them.
The three types of black knife
| Type | Why it is black | Characteristics | Examples in our shop |
|---|---|---|---|
| Black fluorine coating | A black film of fluororesin is applied to a stainless steel blade | Food sticks less. Resists rust. The black at the edge wears off when sharpened | Sakai Takayuki Kurokage |
| Kurouchi (black forged finish) | The black oxide scale formed during forging and quenching is left on instead of being polished off | Common on carbon steel (hagane) knives. Rust is less noticeable. The black fades naturally over time | Kuroiki (玄粋) and Kurotsuchi (玄槌) |
| Black oxide finishes and coatings (titanium, etc.) | A black film is applied over the whole blade | A uniform look. Durability varies greatly from product to product | Not carried in our shop |
What is the wavy pattern (tsuchime) for?
The rippled pattern you often see on black knives is called tsuchime: the dimpled texture left by a craftsman's hammer. The hollows create pockets of air between the blade and the food, so sticky foods like potatoes, daikon and raw meat fall away from the blade more easily. It is not the same as Damascus (a layered, striped pattern): tsuchime is a texture with a function, while Damascus is a pattern on the side of the blade.
Advantages of black knives
- Food releases easily: the slick fluorine coating and the air pockets of the hammered finish mean sliced vegetables don't cling to the blade, so you work faster
- Rust is less noticeable: on kurouchi knives the black scale helps protect against rust, and black fluorine-coated knives are stainless steel underneath, so they resist rust in the first place
- Looks: a knife that becomes the star of your kitchen, and a popular choice as a gift
Disadvantages and things to watch out for
- The black at the edge comes off when you sharpen: where the whetstone touches the edge, both fluorine coating and kurouchi scale are ground away, revealing silver steel. This is not a defect but a sign the knife has been sharpened. The black on the sides and in the hammered texture lasts a long time
- No cleanser or steel wool: they scratch the black layer. Wash with a soft sponge and mild dish soap
- No dishwasher: it damages the black layer and the handle
- Kurouchi carbon steel rusts: toward the edge, where there is no black scale, the blade is bare carbon steel and will rust if left wet. Wash and dry it right after use
Caring for a black knife
- Right after use, wash under running water with mild dish soap and a soft sponge
- Wipe the blade, handle and ferrule dry with a dry cloth
- Sharpen as you would any other knife, on a medium stone (#1000) and a finishing stone. It is normal for the black at the edge to fade
- Before storing a kurouchi carbon steel knife for a long time, apply a thin coat of camellia oil
For more detail, see How to wash a kitchen knife for washing, and our Complete Guide to Knife Care for sharpening.
Black knives in our shop
- Sakai Takayuki Kurokage: VG-10 (stainless) with a hammered finish and black fluorine coating. Santoku 170mm, gyuto 210mm and petty 150mm. From ¥17,800
- Kuroiki (玄粋): a kurouchi santoku in Aogami No. 2 (carbon steel). Holds its edge well and is easy to sharpen. ¥20,980
- Kurotsuchi (玄槌): a kurouchi santoku with a hammered (tsuchime) finish in Aogami Super (carbon steel). The hardest steel in the series. ¥22,980
If you don't want to worry about rust, choose Kurokage. If you want to enjoy the sharpness of carbon steel and the ritual of caring for it, Kuroiki and Kurotsuchi are for you.
What you get when you buy from Hayashi Hardware
First resharpening free (then from ¥1,500 per knife; mail-in available within Japan), a 30-day guarantee for initial defects, and shipping for ¥900 anywhere in Japan (free on orders over ¥30,000). Kurokage comes with the maker's warranty card, and our originals come in a paulownia wood box.
Frequently asked questions
Q. Is it a defect if the black starts to come off?
No. With sharpening and use, the black at the edge fades on every kind of black knife. It does not affect cutting performance.
Q. Do black knives rust?
Kurokage, with its black fluorine coating, is stainless steel and resists rust. Kuroiki and Kurotsuchi, with a kurouchi finish, are carbon steel and will rust if left wet. Either way, the basic habit is to wash and dry the knife after use.
Q. Do I sharpen them the same way as an ordinary knife?
Yes. You can sharpen them on a whetstone. Just be careful not to scrub them with cleanser.
Q. What are the disadvantages of black knives?
The black at the edge wears off, you can't use cleanser or a dishwasher, and kurouchi carbon steel can rust.