When talking about Japanese blades, such as the katana, you often hear people talking about the “hamon.” This visual point is a common characteristic found in authentic and traditional Japanese swords, but it is much more than a simple element of beauty. To better understand the hamon, we look closely at its history, how they are created, the difference they make in a blade, and why a traditional hamon is not common in mass-produced production swords.
What is the Hamon?
The hamon (pronounced “huh-mown”) is the tempering line and point of demarcation on the blade that highlights the harder edge from the softer metal of the spine that a swordsmith creates through differential hardening. In feudal Japan, early swordsmiths learned that the different heating and cooling methods resulted in different properties and, in this case, while the edge hardens quickly and converts to martensite, the spine is kept soft yet strong. Though the spine is softer and shock-resistant the flash hardened edge gains wear-resistant properties which keep it sharper for longer. This point where the steel creates the martensite crystals, known as Nie and Nioi, is what creates the visual appearance of the hamon.
How do Swordsmiths Create the Hamon?
Forging a blade with a hamon is a time-consuming practice and was even more so for early Japanese swordsmiths. After spending days going through the kiln smelting process to create their tamahagane steel and sorting the steel bloom pieces by carbon levels, they then had to go through the process of heating, hammering, and folding the steel to remove impurities before they could even begin to shape the sword. Once shaped, the swordsmith turned to the use of clay and the special coating process to control the tempering process.
The Tsuchioki (Clay)
The tsuchioki, or clay, used for this process was a traditional mixture of clay, polishing stone powder, and charcoal powder, with every swordsmith having their own unique blend. The swordsmith used this thin mixture to coat the spine of the blade, taking care to create their signature pattern with the clay. This process takes time and skill as too thick a layer can allow residual heat to spread to the edge, causing it to soften. In contrast, too thin a layer allows the spine to harden, creating an overall brittle blade. Ideally, the swordsmith wants to create a layer on the spine equal to the thickness of the spine, while keeping the clay at least a centimeter away from the edge as the hamon will extend slightly farther than the edge of the clay placement.
Once applied, the clay must dry completely. This can vary from a few hours to a day or two. If the clay is not allowed to dry completely, it will bubble and flake during the heat treatment. Once the clay is dry, the swordsmith will heat treat the blade.
Yaki Ire (Quenching)
The quenching process is the most critical step in the creation of the hamon. Unfortunately, it is also the point with the highest failure rate. A swordsmith removes the blade from the heat and immediately submerges the blade into water or oil. A pinging sound during this stage marks blade failure. This high rate of blade failure during the quenching process is why differentially hardened blades cost more and why most production swords are monotempered.
Once the blade reaches room temperature, the blade comes out of the quench and the swordsmith carefully scrapes off the clay and proceeds to tempering and polishing to bring out the full effects of the hamon.
On a side note, this quenching process is also what creates the signature curve of the katana blade as the different metals cool. As the spine cools at a slower rate, the change in cooling forces the sword to bend, resulting in the curved blade seen in many Japanese blades.
Kaji-Togi and Togi(Hand Finishing and Polishing)
The first step of the polishing process, the kaji-togi, begins with the swordsmith. This basic polishing allows the swordsmith to detect any defects of problems with the blade before turning it over to the togishi, or polisher. The togishi begins the final polishing process using Japanese polishing stones to bring out the subtle beauty of the hamon.
Benefits of a Hamon
When we talk about the benefits of the hamon, we are really looking at the benefits of the differential hardening process. The hamon itself offers a beautiful visual image to the collector and shows the time and craftsmanship involved in the blade’s construction.
When it comes to blade function, the changes in the metal that the hamon creates are where we see the benefits. A differentially hardened blade, such as the katana, has an average Hardness Rockwell C (HRC) of 50-62 on the edge and 38-45 on the spine while a monotempered blade has an average HRC in the low 50s throughout the blade. What does this mean in terms of benefits? A blade with an authentic hamon offers:
- Blade can be sharpened more than a softer edge
- Blade will retain sharpness for longer
- Softer spine provides extra shock absorption
- Provides superior cutting, even when not particularly sharp, on soft targets
Different Hamon Patterns
No two hamon are exactly alike. However, there are two main classifications: Midare (wavy) and Suguha (straight). The hamon used depends on the preference of the swordsmith and, in some cases can include a combination of both midare and suguha. Some examples of different hamon types include:
- Sughua – This straight pattern can come in hoso-suguha, or narrow, chu-suguha, or medium, and hiro-suguha, meaning wide seguha. The straight pattern is one of the oldest hamon patterns. Expect to see some irregularity in the line as achieving a perfectly straight line is uncommon.
- Ko-Midare – This is one of the oldest wavy patterns, and is considered slightly active, with a minimal wavy pattern. I
- Gunome – This hamon pattern is a midare with a continuous zig-zag wave. A ko-gunome refers to a small wave pattern.
- Sanbon-Sugi – Created by the famous Japanese swordsmith Magoroku Kanemoto, the sanbon-sugi hamon, known as the 3 cedars, is a zig zag gunome pattern.
- Notare – This hamon is known as the billowing wave.
- Choji- This hamon design began in the late Heian period and presents a clove pattern.
Is Your Hamon Real or Fake?
Creating a blade with a real hamon takes time and exceptional skill and, even with that skill, swordsmiths don’t always get it right and the incidence of failure is high. Because of this, most mass-produced blades do not offer an authentic hamon without an additional cost. However, an artificial hamon can be added through etching to give an authentic visual appearance. So how do you tell if your sword is differentially hardened with a real hamon? It depends on how a faux hamon was created. Most are created by polishing the blade in a different direction than the rest of the blade and these “etched” hamon can be visually identified by a “brushed” steel finish to the polish of the hamon.
Unfortunately, a false hamon created with acid or other chemical treatment can often be difficult to distinguish. The only way to truly tell that your blade is differentially hardened with a real hamon is to test the hardness of the edge and the spine. If the hardness is the same, the hamon is definitely fake.
At Kult of Athena, we offer a wide selection of Japanese blades inspired by the traditional swordsmith techniques. You will find a variety of blades that are differentially hardened with an authentic hamon, as well as monotempered blades with or without an etched hamon. We are confident that you will find the perfect sword to meet your needs.
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