There us a traditional order to looking at a blade:
Shape (sugata) tells when it was made
koshi zori: Heian, Kamakura, Nambokucho
torii zori: Nambokucho, Muromachi
saki zori: Later muromachi, Shinto
Taper: how much and where?
Width: motohaba, sakihaba. Width from back to edge
Thickness at the mune: motokasane, sakikasane
Shinogi: high or low. High shimogi gives the blade a diamond cross section. Low shinogi, the planes of the shinogi tend to be parallel.
Shinogiji: narrow or wide
Mune: high or low. iori, maru, or mitsu/
JIgane. tells where it was made:
The steel itself. The color and texture of the metal. The kitae, the quality of the forging. Is it tight. Are there flaws. What kind of flaws?
The jihada: the forging patterns in the steel: masame, itame, mokume.
The hamon: tells who made it
Some very basic steel metallurgy
Pearlitic: softer, more fibrous structure. Lower Carbon, lower temp. slower cooling at quench
Martensitic: Harder, micro structure is small, higher Carbon, higher temp, longer time, sudden cooling
Hamon: the visible phase change between pearlite and martensite.
Nioi: clouds of martensite where the individual grains are not visible without magnification. Nioi deki
Nie: individual grains of martensite visible to the naked eye. Konie to ara nie.
Ji nie: nie on the surface of the blade more or less structured. Nie deki
Basic Hamon shapes
Suguha: a simple, straight pattern. With hundreds of variations!
Midare: irregular. Frequently used in combination with one of the other types as a descriptor, ie. gunome midare (sine wave with irregularities).
Gunome: in a pure form, basically a sine wave pattern. Rarely seen in its pure form. Almost always a combination of midare or choji.
Choji: the Japanese word for clove, a choji hamon resembles a line of cursive m's or n's (peaks with few valleys). Another hamon frequently modified by midare
Notare: a longer wavelength sine wave
Hataraki: activity in the hamon
Ashi: feet. fine line from the hamon to the edge of the blade. They are designed to limit damage from chipping.
Kinsuji: Shining lines. Lines of nie flowng through the hamon. They can appear as either silver or black depending on the angle of the light. If they cross the hamon they are called inazuma (lightning), if they appear in the jihada, they are referred to as chikei.
Sunagashi: Swept sand. Stacked lines of nie in the hamon that look like swept sand.
The Gokaden- The Five Traditions
High shinogi-ji and relatively wide shinogi. Jigane often shows masame and the hamon is suguha or suguha-based in nie-deki which tends to show more horizontal hataraki. Blades look elegant but also strong and with a hint of ancient charm. Flourished from the Heian to the end of the Kamakura, then faded or dispersed.
Rather dense and uniform itame or mokume in combination with a suguha or suguha-based hamon in ko-nie or nie-deki. Blades look elegant and dignified. Yamashiro lost (in sword terms) by the end of the Nanbokuchô period much its significance. Flourished from the end of the Heian to the early Nanbokuchô period. Then dispersed
Jigane in itame or mokume with utsuri in combination with a chôji-midare or gunome-midare hamon in nioi-deki. Blades in Bizen tradition look flamboyant compared to blades forged in the Yamashiro or Yamato tradition. Had its heydays in the Kamakura and late Muromachi period, but was continuously in demand.
Soshu (Sagami no kuni) Den
Larger structured itame in combination with a noticeably nie-laden midareba, notare, or hitatsura. Blades look “wild” and vivid and as the Sôshû tradition was not established before the very end of the Kamakura period, do not expect a blade in one of the (earlier) Kamakura-sugata to be a Sôshû work. Had its heydays in the Nanbokuchô, Muromachi, and Momoyama period. Tends to narrow kasane and the early masters used mitsu mune. When Kamakura was burned and razed, the school dispersed. Huge influence across the country
Jigane shows more or less shirake, i.e. is whitish, and comes in combination with a hamon, mostly a midareba, that shows some concpicuously protruding togari elements, with the sanbonsugi so to speak as its purest Mino-hamon form. As the Mino tradition is the youngest of the gokaden and was not fully developed until the mid-Muromachi period, do not expect a blade in Kamakura or Nanbokuchô-sugata to be a Mino work. Mino was founded by two schools from Yamato in the late Kamakura/Nambokucho (Tegai kaneuji, Senjuin).Early Mino blades have very much a Yamato feel. Later Mino blades look more “pragmatic” in general. Had its heyday in the late Muromachi period.
Yamato and Yamashiro den go back to the earliest appearance of Nihonto as a curved single edged blade. Bizen appears to date as far back. By the late Heian, early Kamakura, all three groups were flourishing and producing beautiful works. Soshu was founded in Kamakura in the late period. Mino was founded by Yamato schools including a student of Masamune from Soshu. It is important to understand that the Gokaden is a late 19th, early 20th century concept, probably created by Honami Koson, as a learning tool for the new interest in nihonto that arose in the Meiji era.
Most of the great swords by the great smiths had been in the hands of the very upper class of bushi and daimyo, and the Kuge or courtier class prior to that. They were the stuff of legend to everyone else. The Edo merchant class could avail themselves of blades made by the famous smiths of the time, but the legendary swords were rarely seen by commoners or even run of the mill samurai.
So the other important thing to remember is that the classic descriptions of the gokaden are based on the Honami family records as polishers and appraisers for the upper reaches of the bushi for generations. In other words, these classic descriptions are based on observations of classic, legendary swords. So they are a tad idealized for the rest of us. Take them too literally, and they will lead you astray, but they are a reasonable guide and outline if you remember that the top smiths have exchanged students, married into each others families, and been called to attend on emperors and shoguns for a thousand years. They communicated and learned from each other. The Gokaden are not as pure as they are depicted in the books.