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Thesis
Read through modern tea science, “襜一曰衣以油绢或雨衫单服败者为之以襜置承上又” is not a lab result but a set of variables: cultivar, soil, light and plucking standard.
Text
“The chan cloth, also called yi, is made of oiled silk or worn rainwear. It is laid on the cheng base, and the gui mold set upon it to form the tea; when a cake is done, it is lifted and replaced.”
Context
襜（chān）：包茶的布，又叫衣。用油绢或旧雨衣做成。放在承上，再放规于其上，用来制茶；茶饼成型后提起换一块。
Evidence
- Collation: 各本一致。吴觉农注：襜为包压茶饼的衬布，油绢可防茶膏粘附，是"脱模布"的唐代版。
- Existing readings: 吴觉农释此句：襜如同今之"压饼垫布"，油绢光滑不粘茶、便于脱模——一件小物，尽显唐代制茶的成熟工序。
Analysis
Modern tea science would split “襜一曰衣以油绢或雨衫单服败者为之以襜置承上又” into cultivar, soil, light and plucking variables. 吴觉农释此句：襜如同今之"压饼垫布"，油绢光滑不粘茶、便于脱模——一件小物，尽显唐代制茶的成熟工序。 They remain testable, but only with their conditions attached.
Conclusion
The section does not give a universal rule. It demonstrates a method: read the text, the annotation and the Tang context together before making a modern claim.
Source: The Classic of Tea, Chapter II · The Implements, section 7; the original is in the public domain.
Experience should be explained, not mystified.