An inkstone’s carved outline is only one part of its manufacture. Yamanashi’s technical account of Koshu Amehata suzuri describes shaping the recesses, successive hand polishing and a later finishing operation. It also connects the stone’s particles with its ink-grinding role.
Technique and structure
The prefecture identifies the raw stone as slate and describes uniform particles called hobo that engage the ink. Separately, the maker carves the inkstone’s internal recesses before polishing by hand with a succession of stones. Material and surface preparation therefore answer different questions from the vessel’s outline. The account does not make a smooth-looking black surface a measurement of grinding performance, and it supplies no universal roughness value to reproduce on another stone.
Read the finishing description precisely
After the polishing stages, the process list describes applying ink over the object and a thin application of stone powder and urushi to its sides, followed by further finishing. That side-specific detail should not be rewritten as a claim that the working surface of every inkstone is lacquer-coated.
The source describes professional manufacture. It is not an instruction to coat or repolish a used inkstone at home, nor a test of a stone offered by an unrelated seller.
For international readers
Ask which stone, working surface and finish belong to the actual piece. A dark colour alone does not identify either the material or the sequence of work that prepared it.
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日本語
甲州雨畑硯：彫った形と墨をおろす石の表面
山梨県は、雨畑硯の原石を粘板岩とし、均一な石の粒子「鋒ぼう」が墨をかむと説明しています。墨池と墨道を彫る仕事の後には、砥石を替えながら手で磨く工程があります。同資料には側面への石粉と漆の塗布も記載され、黒い見た目だけから全表面の状態や、使用済みの硯の補修方法までは判断しません。