Hataraki is a term which is used to define activity overall in blades, but really defines the activity (or "work") *inside* the yakiba. Activities such as yubashiri, chikei, ara- nie, nie fukai, nie utsuri, kinsui, etc., are all nie *based* activities. Nie is basically "spheroidal martensite" which are clumps of martensitic growth propagated by long high heat and maintained in a rapid aggressive quench. For instance, yubashiri is a nie based activity, but is nie in the ji nonetheless. (A feature similar in concentration and location called tobiyaki is nioi based, which is a floating island of nioi based structure in the ji or even the shinogiji.)
Utsuri means "reflection." It is a metallurgical effect induced by the quality and content of the steel and the heat treating done by the smith. Types of utsuri are numerous and share some descriptors with hamon and well as some independent names for other types or styles of utsuri.
Utsuri is identified in the ji of a sword blade as a whitish color extending from the shinogi-ji floating above the yakiba and separated from it by a darker band area in the ji. This darker band is called the "belt". It can be wide or narrow depending on the style, shape, and prominence of the utsuri. The whitish band can be very subtle or outright brilliantly lit when viewed. Some swords require "coaxing" the utsuri to appear and can be difficult to see in lighting inadequate to reveal it. In others, the utsuri can be seen across the room it would seem.
Types of utsuri are numerous and share some of the same names as hamon as well as some names peculiar to utsuri:
The Utsuri can be Nioi based, or Nie based, but both have the concentration extending from the shinogi toward the yakiba, with an identifiable belt region between. It may not be continuous on the length of the blade and can be isolated to certain areas, appear, disappear, reappear, or even form defined "drips" extending down from the shinogi.
Utsuri can be key in identifying particular schools, time periods, smiths, and regions. When utsuri is mentioned casually, it is most often associated with the smiths of the Bizen tradition, and is a key appraisal point for it. Schools of the Ko-bizen, and the Ichimonji are synonymous with florid utsuri with wild choji patterns and deep beautiful glistening color. However, other traditions also can display utsuri. In Yamashiro-den there are the Rai and Awataguchi schools with very prominent, brilliantly created utsuri in nie and nioi respectively. The Ko-Hoki tradition is one that is not really aligned with the Gokaden, and it also can display utsuri.
The actual function and reasons for utsuri are still debated to this day. Speculations on issues of control by the smith, intended purpose, functionality, qualitative indicators, all have been discussed at length. What can be said is that those working in it, worked in it regularly. It's presence in most works will generally set it qualitatively above works produced in subsequent generations that do not display it. It is most definitely a transitional zone or phase in the metallurgical structure, composed of a slightly to significant harder micro-crystaline structure than the belt, but not more than the yakiba. In any case, it was (and still is) a medium that the smith chose to create regularly by the methods and materials he chose. Not every steel composition will support it, and paradoxically, the working methods and heat treating must coincide to create it. The factors for it's creation and presence are exponential in nature.
It is also generally thought that the ability to create utsuri was lost after the Koto period, though there are some examples of smiths creating through and into the 19th century. It's development and "rediscover" was enthusiastically sought by Yoshindo Yoshihara, and he documents it in the book The Craft of the Japanese Sword (Kapp, Kapp & Yoshihara, 1987) with diagrams and specifications for the necessary elements and heat for the effect to develop in a sword. Arguably, this narrow range he describes is not the only formulae for creating utsuri, but is indicative of his particular reproductive requirements. The smith's application of the clay in the heat treating process is also key in it's creation, defining the strength and patter, or lack thereof. However there is speculation and some experimentation that utsuri was a byproduct of actually heat treating done *without* clay. There is merit to this hypothesis and some smiths today are experimenting with the process, furthering the questions of what "ancient ways" actually consisted.
There is yet another type of utsuri euphemistically called "tsukare-utsuri" that, as it's name implies, is indicative of color changes brought about by a blade that is tired and over polished. The color of this utsuri is dull, lifeless, and weak. It is induced by either core steel showing through, or the depletion of the natural heat treating in the jacket steel which has weakened toward the heart of the sword. Shirake-utsuri or "white" is one with duality that can be good or bad based on context. If present where it shouldn't be, it's bad. If present where it should, on say a Zenjo or Kanemoto school sword, then it's good. Again, context plays a part there.
Kapp, Leon., Kapp, Hiroko., and Yoshihara, Yoshinndo. (1987). The craft of the Japanese sword. Tokyo, Japan: Kodansha International.
* Reprinted with permission from the author's original post on Bugei Sword Forums.
** Ted Tenold is a samurai sword polisher in Montana. Nihon-to polished in a traditional manner by him have been awarded Hozon and Tokubetsu-Hozon papers from the Japanese Swords Museum within NBTHK in Tokyo Japan.
Copyright © by Ted Tenold.