A Practical Guide to Appreciating Blade Patterns — Light Application, Angling Techniques, and Tool Usage

The Fundamentals of Blade Pattern Appreciation — Why "How It Appears" Matters

The blade pattern (hadōmon) is both the core of Japanese sword appreciation and, simultaneously, the most challenging subject of observation. This temper-line pattern, which concentrates the individuality of various schools, eras, and sword makers, will not reveal its true form without proper light source and angle. The blade pattern seen through a museum display case and the blade pattern observed firsthand by a sword polisher or appraiser are, essentially, completely different things. In this article, we systematically explain practical procedures for correctly observing blade patterns, from tool selection to light source setup.

Light Source Selection — Differences Between Fluorescent, Incandescent, and Spotlight

The optimal light source for blade pattern observation is an incandescent bulb or high color-rendering LED spotlight (Ra 90 or higher) that approaches point-source illumination. Fluorescent lights and area-emitting LED panels diffuse light, causing blade pattern boundaries to appear blurred. To distinguish the particles of "nie" (whitish specks) and "nioi" (fine texture) in blade patterns, lighting from a single direction with strong intensity is essential.

The ideal observation environment is as follows:

• Light source height: Position 30–50 cm above the blade, angling the light from approximately 45 degrees
• Distance from light source: 50–100 cm is standard. Positioning too close intensifies localized reflections excessively
• Background: A dark blue or black cloth background makes the entire blade pattern, from the temper line to the point, easier to observe
• Blocking external light: Daylight from windows changes direction, so close curtains during observation

How to Angle the Sword — The Meaning of "Tilting" and "Raising"

When the light source angle is fixed, tilting the blade forward and backward dramatically changes how the blade pattern appears. These operations are called "tilting" (taōsu) and "raising" (okosu).

Tilting (angling light along the ridge line direction): The blade pattern rises out in bright white, and the features within the blade (leaves, feet, gold streaks, sand-like flows, etc.) become sharp and clear. This angle is effective for confirming the outline of the blade pattern.

Raising (angling toward the blade edge direction): The grainy texture of nie and nioi becomes pronounced, making it easier to observe the fine details within the blade. This angle is suited for observing features unique to the Soshu tradition, such as "nie collapse" and "gold streaks and zigzag patterns."

Appraisers observe a single blade by repeatedly tilting and raising it multiple times. Observing from only a fixed angle greatly increases the possibility of missing important details.

Handling Polishing Powder and Wiping Paper — Important Precautions Before Appreciation

Polishing powder (uchiko) is used to remove oil from the blade surface, but using polishing powder solely for appreciation is not recommended. Polishing powder particles have an abrasive effect, and repeated use may damage the blade's polished finish. For preservation purposes, using polishing powder once or twice per month is considered appropriate.

The proper procedure before appreciation is as follows:

1. Wipe away oil from the blade using clean wiping paper (washi paper)—without pressing hard, wiping in one direction along the blade
2. After blade pattern observation, apply a thin layer of oil again for protection
3. Do not touch the blade with bare hands (perspiration salt and fingerprints cause rust)

When observing displayed or borrowed swords, follow the owner's or facility's instructions and never wipe oil or apply polishing powder without permission.

Using Magnifying Glasses and Microscopes — Observing Nie Particles

The "nie" (whitish specks) in blade patterns are reflections of metal microstructure (martensite) particles, appearing to the naked eye as a sand-like sparkle. To observe these particles in greater detail, a 10–20× magnifying glass is effective.

Key points when observing with a magnifying glass:

• Hold the magnifying glass close to your eye, adjusting distance from the blade while focusing
• Position your body to block reflected light from entering the magnifying glass
• Confirm whether nie particles are uniform and whether particle boundaries are sharp
• "Coarse nie" and "fine nioi" scatter light differently; observe while keeping this distinction in mind

At 20× magnification or higher, you can also distinguish the shape of nie aggregates, the presence or absence of "double edge," and the direction of sand-like flows within the blade.

Observation Points by Blade Pattern Type

Observation points vary depending on blade pattern type.

Straight edge (suguha): The linearity of the boundary and uniformity of nie are the focus of evaluation. Confirm that the blade edge is not wavy and that no "small irregularities" are mixed in.

Choji pattern: The uniformity of size and shape among each clove-like unit and the presence or absence of "choji feet" at their base are important. Trace the outline of each unit with light tilted.

Gunome pattern: Wave height and uniform spacing are the appreciation points. How one observes the boundary between the gunome and "collapsed gunome" shows the skill of an experienced observer.

Hitatsura pattern: Nie spreads throughout the blade, and boundaries become vague. This pattern is especially observed with light "raised," tracing the spread of nie.

Practicing to Develop Appreciation Skills — The Importance of Repetition and Comparison

Blade pattern appreciation skills are refined through repetitive practice alongside the accumulation of knowledge. In museums, it is effective to visit the same sword multiple times and compare it under different times of day and lighting conditions. Additionally, sword exhibitions and appraisal events provide opportunities to observe swords firsthand, and observing while listening to expert explanations at such venues yields the highest learning effect.

To advance in blade pattern appreciation, the shortest path is combining knowledge from texts and photographs with in-person observation, and developing the habit of consciously controlling the three elements of "light, angle, and distance."