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Thesis
The key words in “第一煮水沸而弃其沫之上有水膜如黑云母饮之则其” are not ornament. They mark where Tang tea names, vessels and provenance meet.
Text
“When the water first boils, skim off the film that rises on the surface, like black mica; drinking it spoils the flavor.”
Context
水膜：头沸水面的浮膜。黑云母：黑色云母片。味不正：味道不正。
Evidence
- Collation: 各本一致。吴觉农注：此"水膜"为水垢与杂质浮沫，撇之使茶汤洁净。
- Existing readings: 吴觉农指出"弃其水膜"是唐代"洁水"的关键一步：水沸后矿物质与杂质浮于表层，撇去则味正——现代煮水同样讲究"刮沫"，此传统千年未变。
Analysis
The annotation matters less as philology than as a distinction between name and thing. 各本一致。吴觉农注：此"水膜"为水垢与杂质浮沫，撇之使茶汤洁净。 Once names settle, picking, grading and trade can share a language.
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 IV · The Vessels, section 8; the original is in the public domain.
Ask what period this person lived in.