Blade of the Samurai

Specimen Notes from the Mini Museum: Samurai Sword Specimen

Summer grass...
  all that remains
     of warrior dreams.

夏草や 兵どもが 夢の跡

Matsuo Bashō (1644–1694)

June 28th, 2017

The Japanese sword is a symbol of unparalleled beauty and quality. Bound closely to the image of the samurai class, the blades are highly prized and honored by collectors all over the world. The history of these incredible weapons and the warriors who wielded them are intimately connected to the development of the Japanese nation and the culture of modern Japan.

Forging a traditional Japanese sword is an intense process. It begins with smelting iron sands in a massive, purpose-built clay furnace known as a tatara. By means of the massive bellows, layers of charcoal and iron sands were kept under constant heat for days, eventually yielding a porous mass of iron, slag, and steel known as a bloom. When complete, the bloom is removed and different grades of steel are separated based on their carbon content - the most famous being tamahagane, a high-carbon, hardened steel with an almost jewel-like appearance.

The oldest blades, known as Ko-tō (Old Sword) were created by combining tamahagane with steel containing both higher and lower amounts of carbon. Kneading or folding this mixture created a material that could be both strong and flexible, provided the blade survived the creation of the ultra hard edge known as the ha. To create the ha, the swordsmith would coat the blade with a combination of clay, charcoal, and crushed stone. This mixture was applied in two steps. First a light coat for the entire blade and then a second, thicker coat for the body. Returning to the forge, the blade would be thermal cycled several times. This process of heating and cooling causes the metal to expand and contract, forcing a molecular reorganization which makes the material denser. The varied application of the clay controls the heat, allowing the edge to become harder while the spine remains flexible. It also results in a beautiful and natural outline of the hardened area, known as the hamon. This way of manufacturing continued for nearly 400 years until the Edo era at the start of the 17th century.

Internal structure of samurai sword blades over time.

The Edo era represented a major change for Japanese society. The previous century was a time of continuous internal conflict. War, famine, and political intrigue among hundreds of local rulers and warlords kept the entire country on edge. Reunified under the Tokugawa clan in 1603, the new shogunate ruled the country from the city of Edo for 265 years, and "the way of the warrior" was transformed into a far reaching philosophy on how to live a moral life.

The strict set of laws which governed the military rule of the Tokugawa shogunate reached into nearly every aspect of public and private life. The rules even dictated the maximum size for both the Katana and Wakizashi swords and the method of manufacture. Tamahagane during this era was mass produced using new methods, which resulted in a steel with much higher carbon content. This made the tamahagane stronger but also made it difficult to combine with other grades of steel. As a result, the new swords or Shin-tō were created using a laminating process which wrapped the harder steel around a softer core. According to polishing experts, older swords were superior in strength and flexibility. This belief led to the cutting down of many longer Ko-tō to fit the blades to the new standard.

Creating the Specimen

The creation of the final specimen for the Third Edition began with the selection of the blade itself, a Ko-tō period katana circa the mid-1300s.

Different angles of the blade, difficult to catch the hamon at the edge because the polish was quite worn

It is a single-forged blade attributed to the Yamato Senjuin School crafted in the area which is now Nara, Japan. Originally, a tachi with a cutting edge of 80cm, the Yamato Senjuin katana is a fine example of an o-suriage sword, or a blade that was shortened to meet the standards of the Edo era (70cm cutting edge or 2-shaku 3-sun using traditional measurements). The blade was selected with the generous support of Pablo Kuntz. Pablo is the owner of Unique Japan, a respected dealer of Japanese swords worldwide. While lovely, the blade has a number of micro-fractures that made it unsuitable, and potentially dangerous, as a collectible but perfect for the Mini Museum.

Close-up of the tip of the sword.

At the beginning of the design process, I knew I wanted the specimen to capture as closely as possible the idea of the samurai sword. This meant that we'd have to prepare very thin slices of the blade which could then be married to the cloth. As I've said before, the difficult part is that the blade is only so long and most of the methods we have for cutting steel of this grade would involve a kerf (the thickness of the cut) which would consume too much of the material. After investigating several options, we settled on a high tech method called Electric Discharge Machining or EDM.

EDM involves rapidly passing a high voltage current through a very thin wire. The cuts are very precise and the kerf is almost non-existent.

Samurai Sword before the first cut - our GoPro is in the water on the left!

The process is slow, almost 8 minutes per slice, so it took several months to complete the initial work. I thought it would be interesting to include the full 8-minute video here so you can get an idea of the entire process:

This is a fairly straightforward cut, but many took much longer as the wire would break when encountering impurities/fractures in the blade. Suffice to say we are very grateful to the talented craftsmen at Winchester Tool here in Virginia. Their expert help was vital!

With the slices in hand, we moved on to the polishing phase. Cutting residue and scorch marks were removed using a lapidary wheel, which is a simple thing to say but in fact it was a very intense, time-consuming process.

Late night outdoors with Mini Museum Helper Billy

It's also a rough process at times. Occasionally, the gloves do give way... but with slices this thin it is important to feel the metal so that the blade slices are not made any thinner.

Ouch! Be careful, Billy!

Of course, even though the blade slices are quite thin the metal is still very tough - and sometimes had a mind of its own!

After working on the wheel, each slice is polished to a bright shine. It's also worth noting here that the add-on slices are also treated using this method with extra time spent on final hand polishing.

Rough Polishing

Below is an image of blade slices during early stages in the process. You can also see the tiny impurities/fractures within the blade that I mentioned earlier.

Early stages of blade slice preparation

Ok, now we're finally ready to make tiny swords!

Even though the slices are quite thin, it still takes a fair amount of leverage to work the shear (not to mention care). Yet, after many hours and many thousands of cuts, we end up with piles of shiny, little swords like these:

Each one of these little swords will be examined and then hand-trimmed to shape a point in the fashion of a kissaki.

Mini Museum Helper Andrea Trimming Swords

With swords complete, we turn to the second half of the specimen: an Edo-period Kataginu, or front vest, which was part of the samurai's formal court attire.

Preparing cloth for resin infusion

To prepare the cloth for inclusion, we infused the fabric with resin to make it firm.

Resin infused cloth curing

Now firm, the fabric could then be cut into straight-edged strips and later the specimen-sized swatches you have in your Mini Museum:

Fabric strips

The final step in the process is carefully marrying the sword to the fabric swatch using just the smallest drop of resin.

Mini Museum Helper Chip placing sword blades.

Getting the angle just right requires patience, as the swords tend to float in the resin.

Samurai Sword Specimens Curing

It's delicate work, but it's also the final step in the long process to produce this stunning specimen!

Samurai Sword Specimen Macro Image

Thank you so much for taking the time to read this post! I hope you enjoyed learning more about all the steps that went into creating the Samurai Sword specimen. I am so happy with the way this particular piece turned out, and I love thinking about each member of the team played a part in creating it.

Now, it’s back to work!

Hans Fex, Creator and Chief Curator for the Mini Museum

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