FAQ

The direct translation of "Kuro-Uchi" is "black-forged." After quenching and heat treatment, the iron oxidizes and turns black as it cools. A Kuro-Uchi knife has the blade directly attached to the blackened blade.

In recent years, polished Japanese knives have become more common, but a polished knife is one in which the black skin of the Kuro-Uchi knife is removed by a specialized polisher. Therefore, compared to polished knives, Kuro-Uchi knives are less expensive because they do not undergo the polishing process, but their sharpness remains the same.

All of our Kuro-Uchi knives are produced in Tosa City, Kochi Prefecture. Japanese swordsmiths moved to Tosa about 400 years ago. Later, Tosa's forestry industry flourished. The production of various blades, such as machetes and axes, with high strength and durability increased, which led to the evolution and deepening of the technique known as free forging.

Today, Tosa is the largest production center for blacksmiths and their skills and supplies forged blades to production centers throughout Japan.

All of our Kuro-Uchi knives are hand-made by master blacksmiths. There are three major processes: Quenching & Forging, Heat Treatment, and Finishing & Sharpening.

Most of our Kuro-Uchi knives are double-edged and made by the traditional forging technique called Hon-wari-komi. Specifically, a crack is made in the base iron (soft iron) that has been quenched in a furnace at 1,000°C, and steel (high carbon steel) is inserted between the cracks and forged (forging). This fuses the different properties of soft iron and steel into a single hard, tenacious, tough blade with a three-layer structure.

There is a process called Honyaki, in which only high carbon steel is used for forging. While high carbon steel is extremely hard and increases sharpness, it has the disadvantage of being prone to cracking and spilling. To compensate for this drawback and increase strength, a structure called Hon-wari-komi was devised in which the blade is covered with soft iron. This structure was born from the Japanese sword manufacturing technique.

First, our store deals directly with knife makers, so there are no middlemen. Second, our Kuro-Uchi knives do not go through the polishing process, which is expensive to work with. As a result, you get lower-cost blades with the same level of quality and sharpness but a more organic look.

A certain amount of work is done to ensure stable and high-quality production. The blacksmiths work on forging and hardening, heat treatment, finish polishing, and handle hanging. Then the work is sent to the next process. For this reason, it is difficult to estimate the production time for a single knife. Still, it generally takes 2 to 3 weeks from the start of production to completion.

There are two major types of steel; high carbon steel and stainless steel. If sharpness is essential, high carbon steel is the way to go; if easy maintenance is better, stainless steel is the way to go.

There are two types of high carbon steel: white steel (No. 1 and No. 2), which rusts easily but is inexpensive, and blue steel (No. 1 and No. 2), which is more expensive but has better sharpness and rust resistance.

Stainless steels include, in order of hardness, powdered HSS, Ginzo, VG10, AUS10, AUS8, VG5, and VG. Generally, professional cooks prefer blue paper, white paper, Ginzo, VG10, AUS10, and AUS8 because of their higher hardness. For the general public, blue paper No. 2, white paper, AUS8, VG5, and VG are recommended.

Learn more about the types of steel used in our blades.

White paper (Shirogami) steel will quickly develop red rust if left wet, so great care should be taken to keep it drained. Blue paper (Aogami), on the other hand, is also called semi-stainless steel because it contains chromium, which is also found in stainless steel and is a rust-resistant steel material. However, rust will occur if left in a wet condition for a long time, so it is crucial to keep it dry. 

Rust is caused by impurities such as phosphorus and sulfur contained in iron. Therefore, the cheaper the steel is, the more susceptible it is to rust. Shirogami and Aogami are both high purity, high-quality steel for cutlery. However, there are still a few impurities that can cause rust. However, our skilled blacksmiths have the technology to remove impurities to the utmost limit during the quenching and forging processes, thus producing blades that are highly resistant to rust.

All steel forged knives are hand-made by blacksmiths. Therefore, strictly speaking, there are slight individual differences in the dimensions of each knife, and long forged blades, in particular, may have slight bends or twists over time, even if they are straight immediately after manufacture. This is the fate and evidence of steel knives made by Hon-Warikomi, forged by blacksmiths.

We check the quality and fine-tune the knives before shipping, but slight bends or twists may occur over time. If you are concerned about them, please have them sharpened or corrected by a specialist. If you need a perfectly straight knife, we recommend a stainless steel knife, which is machine-made and has uniform dimensions.

We recommend the use of grinding stones for edging. Generally, use No. 800 or 1000 for blade preparation and No. 4000 or 6000 for finishing. A sharpener is not recommended because it sharpens the blade's edge at an obtuse angle, making it difficult to get a good sharpness out of the steel.

For cleaning, general detergent can be used. The important thing to keep steel from rusting is to drain it thoroughly and store it in a dry condition. If the blade will not be used for several days, after cleaning, pour hot water, preferably boiling water, over the blade and make sure the water has completely evaporated before wiping it dry and storing it. In this way, any water remaining in the invisible scratches on the blade edge, which can cause rust, will evaporate entirely and disappear and disinfect the blade.

The blade is sharp enough at the point of purchase. However, the entire blade required by professional chefs is generally not performed to avoid spilling the blade during transportation.

If you feel that the sharpness of the blade has deteriorated, you can usually use a medium grind (No. 800/1000) for blade setting and then use a finishing grind (No. 4000/6000/8000) to sharpen the blade and bring out its brilliance. However, if the cutting edge has wholly lost its sharpness and become dull (dull knives), use a rough grind (No. 220) when making small edges to restore a sharp angle to the cutting edge.

All of our listed prices include shipping charges.

Depending on the country and region, we deliver mainly by courier services such as FedEx and DHL, with a minimum delivery time of 3 days and usually within 4–7 days.

Various credit cards, PayPal, and Amazon Pay, are accepted.

Import duties, consumption taxes, and other charges will be calculated by the customs authorities of each country and charged to the customer as the ordering party by the courier service company. Please contact your country's customs office for details.

Orders may be changed or canceled before shipment. We do not accept order changes or cancellations after shipment. We will accept returns only if the product is new and unused, at the customer's expense.

Our products go through a rigorous pre-shipment inspection, but in the unlikely event that an item is unused and has flaws or damage, or if an item is incorrect, we will accept the return at our shipping cost. Please note that we cannot accept merchandise returns after 7 days of receipt.