Behind every step is chemistry and biology. These six articles cover the core craft of each of the six tea categories.
Six crafts in one line: kill-green is putting out the fire (heat kills the enzymes, locking in green); black-tea oxidation is lighting the fire (let enzymatic oxidation run to the end); oolong zuoqing is controlling the fire (only the leaf edges partly oxidise). Yellow-tea men-huang and dark-tea wodui switch “fuel” — to moist heat and microbes.
Four principles run through the chapter: ① enzymatic oxidation is the master switch of tea classification (polyphenol oxidase, PPO, is the “director”); ② the fate of catechins sets liquor colour and astringency (kept → green’s brisk astringency; oxidised to theaflavins/thearubigins → black’s red body; deeply transformed → dark tea’s aged mellowness); ③ aroma is a balance of loss and creation (grassy notes fade, enzymatic and thermal reactions create new ones); ④ amino acids are the steady contributor of umami (the gentler the craft, the more is kept — green, white).
In this chapter
The Science of Green-Tea Fixation
How heat deactivates the leaf's enzyme in minutes, halting oxidation and locking in green tea's colour and freshness.
The Science of White-Tea Withering
White tea is the tea of "subtraction" — no kill-green, no rolling, just long withering and drying. It looks like nothing is done, yet slow water loss and gentle oxidation quietly unfold.
The Science of Yellow-Tea Yellowing (Men Huang)
Yellow tea is like "green tea that takes one more step." After kill-green, the warm leaves are sealed and sweltered so moist-heat turns them from green to yellow — losing grassiness, gaining mellow sweetness.
The Science of Oolong "Bruising" (Zuoqing)
Partial oxidation, sitting between green and black tea, achieved through repeated cycles of shaking and resting. Zuoqing shapes the "green leaf, red edge" and coaxes out oolong's celebrated floral-fruity aroma.
The Science of Black-Tea "Fermentation"
Black tea's "fermentation" isn't fermentation at all — it's an enzyme-driven oxidation that turns colourless catechins into golden theaflavins and red-brown thearubigins.
The Science of Dark-Tea Pile-Fermentation (Wodui)
The first three crafts rely on the leaf's own enzymes; dark-tea wodui hands the lead role to microbes — a true "post-fermentation" that turns polyphenols into theabrownins and makes ripe pu-erh deep, red and mellow.
One thread links all six: oxidation from none to full — green (none) → white (light) → yellow (moist-heat yellowing) → oolong (partial) → black (full) → dark (post-fermentation).