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The two types of shakuhachi are jinashi and jiari (地無し and 地在り). Historically, the first types of shakuhachi were jinashi while jiari came about much later. Jinashi are natural bamboo on the inside of the bore and can have thin coats of lacquer and sometimes lumps for tuning/balance. Conversely, the bore of jiari are completely shaped with layers of thick plaster which is then coated with lacquer. The first jiari were made by applying many layers of a paste called ji, however, today jiari are mostly made using various casting methods which employ epoxy or gypsum plasters. The first individual to be credited with augmenting the inner bore of a shakuhachi with ji-paste was a “Grandmaster” of the shakuhachi named Araki Chikuo (1823-1908).
Ultimately, plastered jiari shakuhachi are easier to make because a predetermined bore profile is cast or formed inside of the bamboo and the length can be adjusted via joints. Conversely, quality jinashi shakuhachi are extremely rare because of the difficulty in acquiring madaké bamboo with ideal dimensions and due to the higher level of skill that’s required to work with such a highly variable material.
Lastly, there are shakuhachi called Hocchiku (法竹) (Hotchiku) which are modern, large bass jinashi. Hocchiku were created and popularized by the master Watazumi (1910-1992). They’re much larger than the jinashi that were used by the Komuso monks of the Edo period. Hocchiku inspired various “spiritual successors” such as Ken LeCosse’s large Taimu or “big nothing”.