A hamon is the temper line produced on a Japanese blade through differential hardening: the smith coats the spine with clay, leaving the edge exposed, then quenches the heated blade in water. The rapid cooling transforms the edge steel into hard martensite while the clay-insulated spine stays softer, and the boundary between those two zones becomes the hamon you see. According to the Japanese Sword Museum and the NBTHK, all hamon types fall into two broad categories: suguha (straight) and midare/midareba (irregular). Within those two families, collectors and kantei practitioners recognize a core set of named patterns.
Here are the eight most common hamon types you will encounter, each with a one-line visual ID:
- Suguha — a straight, even temper line running parallel to the edge
- Notare — a gently undulating, wave-like line with long, soft curves
- Gunome — a repeating semicircular or tooth-like pattern along the edge
- Chōji — clove-shaped lobes that project toward the edge, often in clusters
- Sudareba — a bamboo-blind pattern of parallel, stacked irregular lines
- Tōran (tōran-ba) — large, wave-like billows resembling rolling ocean swells
- Hitatsura — a full-coverage temper that spreads across the entire blade face
- Komidare — a fine, small irregular pattern with tight, closely spaced activity
Key Takeaways
All hamon types fall into two fundamental categories — suguha (straight) and midare (irregular) — and every named pattern is a variation within one of those two families.
| Point | Details |
|---|---|
| Two-family split | Every hamon is either suguha (straight) or midare (irregular); learn this split first before memorizing individual names. |
| Visual ID under raking light | Rotate the blade slowly under a single low-angle light source; the hamon boundary appears and disappears with angle changes. |
| Nie vs. nioi for authentication | Genuine clay-tempered hamon shows nie crystals or nioi cloud under magnification; acid-etched lines appear flat and uniform. |
| Oshigata for records | An ink rubbing captures the hamon’s exact shape independently of lighting and is the standard document for appraisal submissions. |
| Moonswords for clay-tempered blades | Moonswords provides close-up hamon photography and oshigata on request for all clay-tempered katanas in its high-end collection. |
Table of Contents
- What each hamon type looks like: detailed visual cues and variants
- How a smith creates a hamon through clay tempering
- How to view, photograph, and record a hamon
- How to tell a real hamon from an acid-etched or simulated line
- Decoding hamon names: modifiers and compound terms
- Why hamon appreciation rewards patience and cultural respect
- Moonswords carries clay-tempered katanas with full hamon documentation
- Sources
- FAQ
What each hamon type looks like: detailed visual cues and variants
Understanding the names is only the first step. The real skill is knowing what to look for when you hold a blade under raking light. The NBTHK leaflet and Wikipedia’s swordsmithing entry) together provide the clearest reference framework for the patterns below.
Suguha
Suguha (“straight blade”) runs in a clean, unbroken line from the base to the tip. Width is the primary variable, and collectors use four qualifiers: hiro-suguha (wide), chū-suguha (medium), hoso-suguha (narrow), and ito-suguha (thread-thin). Suguha is strongly associated with the Yamato and Bizen traditions of the Heian and Kamakura periods, when functional austerity was the dominant aesthetic. A well-polished suguha blade shows a crisp nioi line with minimal nie activity — the boundary looks almost architectural.
Notare
Notare (“wave”) produces long, rolling undulations that move slowly along the edge, like a calm ocean swell rather than a choppy sea. The wave height and frequency vary: ō-notare has wide, sweeping arcs, while ko-notare keeps the curves tight and shallow. Notare is common in blades from the Sōshū tradition and later Shintō-period smiths. Under magnification, the boundary tends to show a soft, diffuse nioi cloud rather than sharp nie crystals.
Gunome
Gunome (“semicircle pattern”) is one of the most recognizable hamon patterns: a series of rounded, tooth-like projections that repeat along the edge at fairly regular intervals. Markus Sesko’s kantei guide documents numerous subtypes, including ko-gunome (small, tight teeth), ō-gunome (large, prominent arcs), and kataochi-gunome (asymmetric teeth where one side is steeper than the other). Gunome is closely associated with Bizen-tradition smiths and appears frequently in both Kotō and Shintō blades. Mixed forms like gunome-midare combine the regular gunome rhythm with irregular filler activity between the peaks.
Chōji
Chōji (“clove”) produces lobes that resemble the flower of a clove plant, projecting upward toward the edge in rounded, bulbous shapes. It is the signature pattern of the Ichimonji school of Bizen Province. Subtypes include jūka-chōji (layered or stacked clove clusters), kawazu-no-ko chōji (frog-egg chōji with small, round sub-lobes), and chōji-midare (clove forms mixed with irregular activity). The Markus Sesko kantei resource is particularly useful for distinguishing these subtypes, which require close inspection of lobe shape and the nie/nioi activity inside each cluster.
Sudareba
Sudareba (“bamboo blind”) looks like a stack of parallel, slightly irregular lines layered above the main temper boundary, resembling the horizontal slats of a bamboo screen. It is relatively rare and tends to appear in blades from specific Sōshū-influenced smiths. The layered appearance comes from multiple overlapping temper zones, and it can be difficult to distinguish from a poorly polished hitatsura without careful magnification.
Tōran (tōran-ba)
Tōran-ba (“billowing waves”) produces large, dramatic undulations that dwarf notare in scale, with the temper activity rolling up the blade face in sweeping crests. The Japanese Sword Museum attributes the development of this pattern to Sukehiro of Settsu, an Edo-period smith who used it as deliberate artistic expression. Tōran is one of the earliest examples of a pictorial hamon, where the smith’s aesthetic intent is as important as the metallurgical result.
Hitatsura
Hitatsura (“full temper”) covers the entire blade surface with temper activity, including tobiyaki (isolated temper islands) and yubashiri (temper streaks running up the flat). The result is a blade that appears almost entirely bright under polishing light, with the hamon boundary difficult to isolate from the general temper coverage. Hitatsura is most strongly associated with the Sōshū tradition, particularly with smiths like Hiromitsu and Akihiro of the late Kamakura and Nanbokuchō periods.
Komidare
Komidare (“small irregular”) is a fine, tightly packed irregular pattern where the hamon activity stays small in scale but dense in texture. It is often described as a miniaturized midare, and it appears in blades from multiple traditions. Under magnification, komidare typically shows strong nie activity — individual martensite crystals visible to the naked eye — giving the boundary a sparkling, granular quality.
On mixed patterns and hamon patterns: a hamon pattern alone does not determine blade quality. Many of the most celebrated blades carry simple suguha, while some elaborate pictorial hamons appear on relatively ordinary steel. The pattern reflects the smith’s intent and tradition, not a hierarchy of value.
For visual reference, the Wikimedia Commons hamon repository hosts a broad collection of photographs and oshigata that you can use to cross-check what you see on a blade against documented examples.
How a smith creates a hamon through clay tempering
The hamon begins with tsuchioki — the application of a clay mixture to the blade before the final quench. The smith applies a thick layer of clay to the spine and sides, then draws a thinner layer or leaves the edge area largely bare. The profile of that clay boundary is what determines the hamon’s shape: a straight clay edge produces suguha, a scalloped or lobed clay edge produces gunome or chōji.
Once the clay dries, the smith heats the blade to the correct temperature (judged by color in a darkened forge) and plunges it edge-first into water or oil. The unprotected edge cools almost instantly, locking the steel into hard martensite. The clay-insulated spine cools slowly, allowing the steel to settle into softer pearlite and ferrite structures. The boundary between those two zones is the hamon.
Several variables shape the final pattern. Clay thickness and profile are the most direct controls, but quench speed, water temperature, steel carbon content, and the quality of the polish all affect how the hamon appears to the eye. A blade polished to a high degree will reveal nie and nioi detail invisible in a rough polish. The historical evolution of katana design tracks how smiths refined these variables across centuries to produce increasingly controlled and expressive hamon.
How to view, photograph, and record a hamon
Capturing a hamon accurately — whether for your own records or to share with an appraiser — requires the right light, the right angle, and a little patience.
- Set up raking light. Position a single light source (a desk lamp or a narrow LED panel) at a low angle to the blade, roughly 20–30 degrees from the flat. Overhead or diffuse light washes out the hamon boundary entirely.
- Rotate the blade slowly. The hamon boundary is a crystalline structure, not a painted line, so it appears and disappears as you change the viewing angle. Move the blade in small increments until the nioi line snaps into focus.
- Check the polish state first. A blade in rough polish or with surface rust will not show nie and nioi detail clearly. Clean the blade with a soft cloth and a drop of chōji oil before inspection, following standard sword maintenance practices.
- Use magnification for nie/nioi detail. A 10x loupe or a macro lens attachment for your phone reveals whether the boundary is made up of individual nie crystals (bright, coarse sparkle) or a diffuse nioi cloud (fine, misty glow). This distinction matters for authentication.
- For DSLR or mirrorless photography: use a macro lens (90–105mm range), set aperture to f/8–f/11 for depth of field, and shoot in RAW. Avoid on-camera flash — it creates flat reflections that erase the hamon. A single off-axis speedlight or a strip softbox at a low angle works well.
- For phone photography: enable manual focus or use a clip-on macro lens. Tap to focus on the hamon boundary, not the flat of the blade.
Pro Tip: For oshigata (ink rubbing), lay the blade flat on a padded surface, place thin washi paper over the blade, and rub gently with a soft ink pad or graphite stick. The hamon boundary, hada (grain), and hi (grooves) will transfer to the paper. Label the oshigata with the blade’s length, date, and any known smith attribution — this becomes a permanent record useful for future appraisal.
Oshigata are particularly valuable because they capture the hamon’s exact shape independent of lighting conditions. The Wikimedia Commons hamon collection includes numerous oshigata examples you can study before making your own.
How to tell a real hamon from an acid-etched or simulated line
This is the question that matters most when you are assessing a purchase or an inherited blade.
A genuine clay-tempered hamon has a boundary made of actual crystalline microstructure. Under magnification, you will see either nie (individual martensite crystals that appear as bright, coarse sparkle) or nioi (a fine, misty band of smaller crystals). The boundary is not a sharp, mechanical line — it has organic variation, and the activity inside the yakiba (tempered zone) includes features like tobiyaki (isolated temper islands above the main line) and kinsuji (bright, hair-thin lines of martensite running through the temper zone). These features cannot be faked with acid.
An acid-etched line, by contrast, looks flat and uniform under magnification. The boundary is often too crisp and too consistent, with no variation in crystal activity from one inch to the next. There is no nie sparkle, no tobiyaki, and no kinsuji. The “hamon” on a stainless steel or low-carbon blade is almost always acid-etched, because those steels cannot form martensite through differential hardening.
When assessing a seller’s listing, request the following before committing:
- Full-face close-up photographs under raking light, showing the nioi/nie boundary
- Oshigata, if available
- Polish history (who polished it and when)
- Any previous appraisal documentation
For formal authentication, the NBTHK (Nihon Bijutsu Token Hozon Kyokai) offers kantei (appraisal) services that provide a written judgment on a blade’s authenticity, attribution, and condition. An NBTHK kantei paper is the most widely recognized authentication document in the Japanese sword collecting world. The Japanese Sword Museum also provides guidance on appraisal routes and what documentation to prepare.
Pro Tip: When contacting a seller, ask specifically: “Can you provide a close-up photograph of the nioi/nie boundary under raking light, and an oshigata if one exists?” A seller with a genuinely clay-tempered blade will usually be able to provide both. Hesitation or a refusal to supply magnified hamon photos is a meaningful signal.
Decoding hamon names: modifiers and compound terms
Japanese hamon names follow a consistent grammar once you know the building blocks. The Wikipedia swordsmithing article and the Markus Sesko kantei guide together cover the most important modifiers.
| Modifier | Meaning | Quick visual cue |
|---|---|---|
| hiro | wide | yakiba occupies a broad band near the edge |
| chū | medium | standard yakiba width |
| hoso | narrow | yakiba is a thin band |
| ito | thread-thin | yakiba barely visible as a fine line |
| ō (ō-) | large / big | pattern elements are large in scale |
| ko (ko-) | small | pattern elements are fine and tight |
| midare / midareba | irregular | mixed or non-repeating activity |
| -ba / -ha | “blade” suffix | indicates a named hamon style (e.g., tōran-ba) |
| kata- / kataochi | one-sided / falling | asymmetric element (e.g., kataochi-gunome) |
| -gashira | “head” | refers to the top or peak of a pattern element |
Common compound names you will encounter in auction catalogs and kantei descriptions:
- Gunome-midare — gunome rhythm with irregular filler activity between the peaks; one of the most common mixed forms
- Notare-midare — long notare waves with irregular activity riding on top
- Chōji-midare — chōji lobes mixed with irregular midare; associated with Bizen-tradition blades
- Kataochi-gunome — gunome where one side of each tooth is steep and the other slopes gently
Once you can parse these compound names, a phrase like “hiro-notare with ko-gunome and tobiyaki” becomes a precise visual description rather than an intimidating string of Japanese terms.
Why hamon appreciation rewards patience and cultural respect
Most collectors come to hamon through aesthetics — the visual drama of a tōran-ba or the quiet authority of a fine ito-suguha is genuinely arresting. But the longer you study blades, the more you realize that hamon appreciation is inseparable from understanding the tradition that produced it.
The shift from simple suguha in early swords to the elaborate pictorial hamons of the Edo period was not purely decorative. It reflected changing patronage, shifting battlefield needs, and the growing role of the sword as a cultural object rather than a purely functional weapon. By the 17th through 19th centuries, smiths were producing hamons that depicted waves, landscapes, and natural forms — Sukehiro’s tōran-ba being one of the most celebrated examples. That history matters when you are assessing a blade, because a hamon style that is anachronistic for a claimed period or school is one of the first flags an experienced kantei practitioner looks for.
Provenance and condition should always take priority over aesthetic hamon preference when you are valuing a blade. A suguha blade in excellent polish with documented provenance is worth considerably more than a spectacular chōji-midare with an uncertain history and a compromised polish. When handling museum pieces or privately owned blades, use cotton gloves, support the blade from below, and never apply pressure to the edge or hamon zone. The display care guidance for serious collectors covers the practical steps for preserving hamon appearance over time.
Moonswords carries clay-tempered katanas with full hamon documentation
If you are ready to own a blade with a genuine, hand-forged hamon rather than an acid-etched line, Moonswords offers a range of clay-tempered katanas forged by master artisans using traditional differential hardening techniques. Every blade in our high-end collection undergoes clay tempering, and we document the resulting hamon with close-up photography under raking light.
Before you purchase, you can request high-resolution hamon photographs showing the nioi/nie boundary, and oshigata where available. Our team works directly with the forge to pull these images for you — so you can assess the temper line with the same care you would apply in person. For buyers who want an explicitly clay-tempered tamahagane blade, the Kyōjin 狂刃 Katana is a strong starting point. Browse the full collection at Moonswords and contact us before checkout to request your hamon documentation package.
Sources
FAQ
What are the main hamon types on a Japanese sword?
The two fundamental categories are suguha (straight) and midare (irregular). Common named subtypes include notare, gunome, chōji, sudareba, tōran-ba, hitatsura, and komidare, each with distinct visual characteristics.
How can you tell a real hamon from an acid-etched one?
A genuine clay-tempered hamon shows nie crystals or a nioi cloud under magnification, along with organic features like tobiyaki and kinsuji. An acid-etched line looks flat, overly uniform, and shows no crystalline activity under a loupe.
Which hamon type is considered the most prestigious?
Prestige depends on tradition and context rather than a single ranking. Fine ito-suguha on a well-documented Yamato blade and elaborate jūka-chōji on an Ichimonji blade are both highly regarded, but provenance and polish condition carry more weight in valuation than pattern preference alone.
What does the NBTHK do for sword collectors?
The NBTHK (Nihon Bijutsu Token Hozon Kyokai) provides formal kantei appraisal services that authenticate a blade’s origin, period, and condition, issuing written papers that are the standard authentication documents in the Japanese sword collecting world.
What is oshigata and why does it matter?
Oshigata is an ink rubbing of a blade that captures the hamon shape, hada, and other surface features as a permanent, light-independent record. Appraisers and kantei practitioners use oshigata to study and compare blades without requiring physical access to the sword.