Blade Polishing Techniques Introduction: After forging, heat treating, and rough polishing have been completed, the swordsmith is ready to hand the blade over to the expert polisher, or "togishi", for final polishing. It's during the final polishing process that the true artistic beauty of the blade will be revealed. Polishing, when done properly, will bring out all of the subtle features present in the blade such as the jihada (grain), the hamon (heat treated edge), the nie and nioi (fine particles of high carbon steel), and any utsuri if present. WARNING: Do NOT attempt to polish a Japanese sword or naginata yourself. More blades are permanently damaged by amateurs attempting to polish them than by any other means! The art of blade polishing has been developed and refined over a period of at least 1,000 years, and is a highly complex process which is far more difficult than ANY other type of metal polishing. These blades are composed of thousands of layers of metal, all of which vary in their carbon content and subsequently their hardness. The Japanese use a combination of both artificial and natural (quarried) stones during the polishing process. This means that polishing is accomplished by both abrasive AND chemical means. Ordinary carbide papers, jeweler's rouge, cerium oxide compounds, "silver polish", etc. will simply not provide the same type of polish and will most likely ruin the blade. Furthermore, do not try to polish a blade by using a buffing wheel!!! This damages the steel by causing localized heating which then alters its microcrystalline structure.
Kaijitogi: Rough Polishing Before turning the blade over to the polisher, most swordsmiths give it a rough polish. This is done in order to firmly establish the blade's lines and geometry, and to make sure that no hidden flaws such as cracks or defective welds are present. The swordsmith, out of respect for his fellow craftsman, would not want to pass along anything less than a perfect blade. Using a metal file, the smith will also file the nakago (tang). This will be done in a characteristic decorative pattern; usually in the form of simple slanted lines. He'll use this pattern consistently on all of his blades, since it's considered one of his "trademarks" that can later be used to help distinguish his work from counterfeits. He'll also:
inscribe his mei (signature) and any other information requested by its owner.
drill the hole in the nakago for the mekugi (retaining peg). The nakago will never be polished or cleaned throughout the lifetime of the blade since the amount of rust on it, as well as the appearance of the rust, is frequently used as one of the means of determining a blade's age.
add any decorative hi (grooves) or horimono (decorative carvings) if they have been ordered. The hi are usually carved by the apprentice. The apprentice uses a drawknife, fitted with various sizes of cutting blades, to carve them. A set of grooves on a long blade can take up to two days to carve. The smith may carve the horimono himself, or send the blade to a specialist for this task. After the hi and horimono have been carved, the blade is ready to be turned over to the professional polisher.
Polishing Schools There are currently two schools in Japan which teach the art of blade polishing:
The Honnami School: The Honnami school is the most well known, and is the stricter of the two. The Honnami family has been appraising swords and teaching sword polishing since at least the 13th century. Students in the Honnami school typically spend their first two years learning how to do foundation polishing. They then spend the next three years learning how to do finish polishing. Only after this amount of training has been completed are the students then allowed to polish an entire blade from start to finish.
The Fujishiro School: In contrast to the Honnami school, students in the Fujishiro school rapidly progress from one stage to the next. Instructors in the Fujishiro school feel that students will readily see the effects of mistakes made during foundation polishing if they also do the finish polishing on the same blade. Both schools typically require their students to undergo a ten year apprenticeship before they are certified to work independently.
Regardless of which school he attended, the polisher needs to be highly skilled in his ability to appraise swords. By simply looking at the blade he must be able to tell how, where, and when it was forged. Depending on the time and place in which the blade was originally made, it will respond differently to the stones used in the polishing process. The polisher must also be able to determine whether or not the blade can sustain another polishing. Since polishing is an abrasive process, the blade can only be polished a limited number of times before the polisher risks grinding thru the "jacket" steel, or through the hamon; thereby destroying the blade. It will take the polisher 10-14 days to complete the polishing process. If the blade is properly cared for, this polish should last approximately 100 years. Shitajitogi: Foundation Polishing In order to effectively do his work, the polisher sits on a low stool directly in front of the polishing stone. Water, which is used as a lubricant, is located in a large bucket adjacent to the polishing stone. The polisher's right knee is tucked up almost into his right armpit, and his right foot rests upon a wooden clamp which holds the polishing stone in place. This posture enables him to exert pressure evenly onto the blade, and to carefully monitor the progress of the polishing. By simply lifting up on his right foot, he can release the clamp and change polishing stones quickly. Most students find this posture very uncomfortable to adapt to for the first 6-12 months or so. The polisher uses a variety of stones, both natural and artificial, to accomplish his task. Listed below are only some of the BASIC ones. Since each blade has been made slightly differently, the polisher must make constant changes in his selection of stones in order to bring out the artistic patterns and features hidden in the steel. The first three stones are very rough and are only used on newly forged or badly rusted blades (it takes one to two days of continuous work to redefine the lines of a badly rusted blade). The stones typically used in this process are:
Arato: 180 grit; natural sandstone or carborundum
Binsui: 280-320 grit; natural sandstone
Kaisei: 400-600 grit; natural sandstone
During foundation polishing, the polisher holds the blade with the edge facing away from him; moving it back and forth over the stone with short strokes. Depending on the hardness of the stone being used, the polisher may also incorporate a slight rocking motion during the stroke. He first polishes the mune, and then moves on to the shinogi ji, kissaki, and ji. In all cases, he starts with the end closest to the nakago; slowly working his way along the length of the blade then back down the other side. As the polisher moves on to the next finer stone, he changes the angle of the blade slightly so that the scratches from the previous stone will be readily discernible from those induced by the new stone. In this way, he'll be able to tell when he has thoroughly removed the damage caused by the previous stone. After the polisher has finished the foundation polishing, the blade's lines will be firmly established and no further changes should occur in them. At this point the hamon is also beginning to become visible. This is more visible in Shinto and Shin-shinto blades since they tend to have a more pronounced hamon.
Intermediate Polishing The next step is the nagura stones. There are two type of nagura stones:
chu-nagura: 800 grit. Can be either natural or artificial.
koma-nagura: 1,200-1,500 grit. This stone is always a natural stone.
Following the nagura stones are the uchigumori stones. At this stage in the polishing process the hamon is clearly visible. Only natural stones will be used from this point forward. The polisher must now constantly watch for any defects inherent in them which could cause scratches. Uchigumori stones have a grain size of approximately 3,000 grit. There are two types of uchigumori stones:
uchigumori-ha-to: this is used on the entire blade to remove scratches left by the komo-nagura stone, and to clarify the hamon.
uchigumori-ji-to: this is applied only to the edge and the sides to expose the jihada present just above the hamon. From this point forward, the mune and the area above the shinogi (ridgeline) will not be polished. Instead, they'll be burnished to a bright finish.
Shiagetogi: Finish Polishing The stones used in the finish polishing process are in the form of paper-thin wafers. They are about one inch square, and are held in the fingers; hence the name "finger stones". These finger stones are actually small pieces of stone that have been glued to translucent paper and lacquered together. The use of the finger stones will highlight the subtle features in the steel, such as the nie, nioi, and utsuri. An entire day is frequently spent on just one stone. Some of these stones include:
Hadori (hazuya): hazuya stones consist of thin pieces of uchigumora stone that have a special lubricating "paste" on them. This paste is made by rubbing pieces of uchigumori stone together and then mixing this residue with sodium bicarbonate. The paste is then applied to the blade and rubbed with the uchigumori stone. After this is completed, the surface of the steel will become cloudy and white.
Jizuya: the jizuya stone is made from paper-thin pieces of narutaki stone that have been adhered to paper and then lacquered. Use of the jizuya stone causes the steel to become darker. Most importantly, the jihada begins to become more visible.
Nugui: this is the final step in the polishing process. Nugui is a fine suspension of iron oxide particles mixed with vegetable oil. As with the jizuya stone, the nugui darkens the steel, which helps highlight some of its subtle features.
Customizing the Hamon's Appearance The appearance of the hamon can be altered by the selection of either the hadori finish or the sashikomi finish. Some collectors, as well as many NBTHK judges, prefer that the hamon be white. This is done by polishing the area with a hadori (hazuya) stone. Hadori stones highlight the hamon by whitening it. However, in doing so, some of it's features will be clouded. For collectors that are more interested in seeing the details of the hamon, the hadori step is omitted and in its place a sashikomi finish is applied. This is accomplished by the use of a different type of nugui compound (tsushima, kujaku, or jitekko) after the jizuya step. Use of any of these nugui will selectively darken the ji, making the hamon stand out sharply in contrast; ensuring that all of the subtle details present in the hamon are clearly visible.
Glossary of Terms
hamon: the artistic pattern of heat-treated steel
hi: decorative grooves which extend along much, if not all, of the blade's length
horimono: decorative carvings
ji: the area between the heat-treated edge and the ridge line
jihada: extremely fine grain in the steel which can only be seen after the blade has been properly polished
kissaki: the tip of the blade
kodogu: beautifully crafted fittings which are put on the sword's handle and scabbard
mei: the smith's signature which is engraved in the nakago (tang)
mekugi: a bamboo retaining peg used to keep the blade firmly seated in the sword handle
mitsu-gashira: the "triple point" in the blade's tip where the ko-shinogi and yokote lines meet
mune: the top of the blade (opposite to the cutting edge)
nakago: the tang, or steel "handle" which fits inside the decorative handle
nie: small spots of high carbon steel present just above the hamon
nioi: spots of high carbon steel which cannot be resolved with the unaided eye, and instead appear as a subtle white mist. Usually associated with nie.
saya: the scabbard
shinogiji: the area just above the ridge line; between the ridge line and the mune
Shin-shinto: swords made after 1868
Shinto: the "New Sword" period; from 1530-1868. Blades made before this time are referred to as "Koto"
utsuri: "reflection". A whitish effect occasionally found on the sides blades. This is formed only under precise conditions of temperature and metal composition. Its exact metallurgy has yet to be confirmed, but it is believed to be composed of a complex matrix of ferrite and pearlite microstructures.
yakiba: the heat treated edge (frequently referred to as the hamon)
yokote: the small vertical line in the blade's tip
Conclusion After the blade has been properly polished, it's true beauty and luster should be quite visible, and trained observers should readily be able to see all of the subtle features present in the steel. The blade is now ready to be sent to the other craftsmen who will make the saya (scabbard) and kodogu (fittings). In the next article in this series, these crafts will be examined in more detail.