JAPAN
The Kudaru-tsuchi is a pure white substance, similar to chalk. It is friable and greasy to the touch, but less so than a true clay. In water it immediately disintegrates to powder, giving off air bubbles, but in the mass it has very little plasticity. It remains white after heating.
The Seiji-tsuchi has a much coarser grain than any of the preceding minerals, and a distinctly laminated structure. Although generally white, it is stained in places by limonite.
The Shirakawa-tsuchi has a finer grain than the Seiji-tsuchi, but coarser than any of the other varieties. It is white, with brownish stripes and spots; porous, rough to the touch, and friable only to a small degree.
It has been already stated that Izumi-yama furnishes a stone which, from the time of its discovery, served for the manufacture of the porcelain mass without any addition of foreign matter. But the reader will see from the above table that the Arita mineral presents varieties which, though differing very slightly in composition—excepting, of course, the Kudaru-yama-tsuchi which belongs to another category—are nevertheless sufficiently unlike to suggest that something might be gained by intermixing them. The Hizen potters early appreciated this possibility. They certainly combined these various stones, using the Tsuji-tsuchi and the Shiro-tsuchi as the principal materials of the porcelain mass. The former, the purest and whitest of all, being somewhat intractable in the kiln, is mixed with Shiro-tsuchi, in the proportion of 7 to 3, for the manufacture of egg-shell ware. The Shiro-tsuchi and Sakaime-tsuchi are accounted of equal quality, and are mixed in varying proportions, equal parts being taken to form the mass of common thick Arita porcelain. The Shirakawa-tsuchi is combined with Shiro-tsuchi or Sakaime-tsuchi to produce crackled porcelain. The Uwagusuri-tsuchi is used for glazing purposes, and the Seiji-tsuchi is similarly used in the manufacture of céladon (Seiji).
The first five minerals enumerated in the above table are found within a comparatively small district in the neighbourhood of Izumi-yama. They do not occur in strata, but are embedded here and there, and covered by felspathic rock.
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