When it comes to swordsmithing, the hamon (which literally translates to blade pattern) is generally a visual effect produced on the blade via a hardening method. The hamon is considered as the outline of the yakiba (hardened area) which features the ha or cutting edge. Blades that have been crafted in this manner are usually referred to as differentially hardened weapons and these feature a harder cutting edge than a mune. The difference in hardness is due to the clay being applied to the blade before it even undergoes the quenching process. Less to no clay lets the blade’s edge cool faster, making it harder yet more brittle; when there is more clay present, this allows the spine and center to cool much slower, thus, retaining more of its resilience.
The hamon also outlines the development between the portion with the harder, more compact martensitic steel found right on the blade’s edge, as well as the softer pearlitic steel found at the back and center of the sword. The difference in hardness is the primary goal of this process while its appearance is simply just an additional effect. However, the hamon’s aesthetic features are generally valuable – not only as an evidence of differential hardening but also in artistic value; as for the patterns, these can also be complex as well.
A lot of present-day reproductions do not feature a natural hamon since these are intensely hardened mono steel; also, the hamon’s appearance is reproduced using different methods such as sandblasting, acid etching, and even more crude processes such as wire brushing. A couple of the contemporary reproductions featuring natural hamons are also likely to receive acid etching since it improves the prominence of their hamon. A real hamon can easily be identified simply by the presence of the nioi – a bright, dotted line that follows the hamon’s length. It is generally best seen at longer angles and can’t be faked via etching or other processes. When viewed via magnifying lens, the nioi appears just like a sparkling line made up of numerous bright martensitic grains that are usually surrounded by softer and darker pearlites.
Different Types of Hamon
- The Suguba – Straight
This hamon line has been utilized since the time when the Japanese began manufacturing swords until today. It was commonly utilized by all the primary schools with different types of variations. The suguba may also be classified according to the width of its hamon: the hiro suguba for a wide hamon, the chu suguba for a medium-sized one, and the hoso suguba for the narrow hamon.
This specific type of hamon was used from the Heian era to the present day and it refers to the irregular patterns of the hamon. All of the hamons (except the suguha) have the midare hamon and here are its sub-types: the ko midare for a small midare, o midare for a large one, and the saka midare for a slanted type.
- Choji Midare – The Clove Pattern
The choji midare is the hamon that features choji shapes. Its upper part is roundish while the lower portion is somewhat narrow and constricted. This was utilized from the late Heian era to the present day and numerous types of these were developed for use. The variations of the choji midare consist of the ko-choji midare – small and clove-shaped with an irregular pattern, o-choji midare – a large clove-shaped piece with irregular patterns, jika-choji midare – choji that has a bag shape, the kawazuko choji midare – choji with a tadpole shape, and the saka choji midare – the slanted choji midare.
It was used during the Kamakura era but when the Shinto period came, different types were created from the classic design. During the Muromachi era, Kanemoto made the sanbon-sugi gunome popular for its slicing abilities.
- Obusa Choji
Obusa means the shape of a hamon’s head which appears like a bunch of chojis.
- Kataochi Gunome
These are flat-topped gunomes that slant just like saw teeth; the kataochi gunome were also referred to as the nogirimidare and nokogiriba.
- Notare – The Billowing Waves
Also utilized during the Kamakura era until today; the Soshu School was famous for utilizing this for their hamons. The notare could also be classified as the following: ko notare and the o notare.
- Sanbon Sugi
This is a sub-type of the togari gunome with repeating 3 peaks that appear just like cedar trees.
- Full Hitatsura
Another one that has been utilized by the Soshu School during the late Kamakura era; it became famous around the Muromachi era by the other main schools.
- The Sudare / Kikusui-ba
This was developed in the Shinto era where a small group kept the style until the Shinshinto era.
- Fuji Yama
The Fuji Yama was developed from the notare midare plus a gunome in the hamon. It was later modified in the year 1600 to appear like Mount Fuji.
- Togari Gunome
This gunome has orderly and pointed peaks; the pattern is located in the swords of Sue Seki and other connected schools.
Hamon patterns that appear like large, surging sea waves
- Uma Ha
A hamon pattern that is shaped just like horse teeth; the uma midare refers to irregular uma ha.
The yahazu is a hamon that resembles a fishtail or arrow notches.