Manufacture, Function and Material of Early Iron Tsuba
Early iron tsuba share material as well as functional affinities based on quality of
metal, forging techniques, carbon content and presence of impurities.
Tsuba were created to endure battle
conditions and protect the user from grave injury. In this context, it would follow that
one should be able to analyse the product from contemporaneous tsubako and katchushi,
and be able to make informed comparisons of technique, material and possibly even age
and place of manufacture.
Many scholars believe
that early iron tsuba evoke an emotional response
which later (
Period) iron tsuba fail to elicit. The limited decorative features of a tsuba in the Sengoku
period captured the desperate yet hopeful mood of turbulent times, therefore, these tsuba
tend to have a subtle elegance yet deeply expressive quality. Such early tsuba were
utilitarian items, designed for potential use on the battlefield, and thus it reasonable to
assume that their owners placed demands on the tsubako to produce a quality product.
The iron quality, construction
and aesthetic all seem to lose functionality, to be replaced
by emphasis on artistic qualities during the
Perhaps the two most important and characteristic, and yet most poorly understood
aspects of early tsuba manufacturing techniques are 1) folding of the metal and 2)
heterogeneous carbon distribution. As collectors we look for these features manifested as
fold or weld lines and
various forms of tekkotsu (iron bones)
respectively. Tekkotsu may
be defined as segregated areas of high carbon content, formed as a result of
a process of successive episodes of heating, folding and hammering of an iron plate.
Generally speaking, increasing the carbon content in iron, results in decreased ductility.
Thus, a localized area of high carbon content (tekkotsu) effectively forms a localized hard
spot. These localized areas of decreased ductility tend to interfere with crack propogation
by deflecting or blunting
the crack. These attributes are often used as indicators to distinguish
older and higher quality tsuba, however, many collectors fail to understand just why this is so.
From a mechanical perspective, both folding and carbon distribution alter the stress
behavior of the iron tsuba in ways which increase resistance to impact. Folding iron
greatly increases resistance to ballistic and notch-impacts by dissipating the impact
energy from effectively a point or line source to a greater surface area provided through
successive planes of laminated material that tend to shear or delaminate rather than
The combination of the laminated plate of a tsuba, with heterogeneous carbon is thus a
very effective crack arrestor. Evidence of this is seen in the thinness of the earliest iron
tsuba. Perhaps the tendency to thicken the rim and/or plate of a tsuba toward the end of
the Muromachi period is attributable to attempts to find balance between tsuba integrity
and the call for increasing amounts of artistic design elements via sukashi in a tsuba
meant for the battle field.
Another consideration in understanding early iron tsuba is material – is the tsuba
composed of high carbon steel or iron, and what are the implications of this distinction?
Kremers (1994) briefly addressed the question of steel vs. iron, pointing out the main
problems as being the difficulty in distinguishing between the materials in an old tsuba,
and in identifying the possible source of the materials employed in the manufacture.
The high degree of variance among Muromachi tsuba suggests that a potentially large
number of independent artists scattered throughout the country were responsible for
production. Iron ore extraction in
records indicate that a number of ore deposits were exhausted at various times during the
Muromachi, and resource replacement was a constant issue, especially during times of
civil war when the demand for iron surged. This would suggest that iron qualities varied
regionally as well as through time. It is reasonable to assume that iron
Kremers and others have suggested, that they may have been instrumental in avoiding
wastage by re-using scrap materials.
The implications are that some tsuba were made as secondary products of early sword
manufacturing shops, while others were made as secondary items by some armor
manufacturers. As usual, modern nomenclature sways us into potentially
erroneous associations. The term kokatchushi tsuba was applied first to early iron tsuba
whose sukashi motifs, robust mimi and iron character reminded people of some late
Muromachi mempo and hachi. The term kotosho was based on observations by some
scholars of metal similarities between certain early iron tsuba and the metal of sword
tangs. Both terms are thus based on subjective observations, and
yet they have been broadly incorporated, and likely over-used.
If these terms are reflective of manufacture, then kotosho tsuba
should be made of highly refined iron or steel that was likely folded, and associated with
blade manufacture. Kokatchushi tsuba would then be made from scrap metal used in the
production of armor, which may have been folded, but generally more iron-like in feeling
I think the safe and most reasonable approach is to recognize the tremendous variety in
early iron tsuba, and that many groups or independent producers utilizing a wide range of
methods were actively engaged in their production, and often participated with others
with materials and ideas. This participation may well have come from groups
involved in the production of armor or swords, but the actual physical or documented
evidence of such an association is non-existent.
Return to Tsuba
Return to Tsuba