---
type: Concept
title: Tea Processing
description: How Chinese tea tradition's six classes — white, green, yellow, oolong,
  black, and dark — are defined by how far and by what mechanism (enzymatic vs. microbial)
  the leaf changes after picking, plus the sheng/shou split within pu-erh.
tags:
- tea
- processing
- oxidation
resource: raw/tea-processing-and-cultivars.md
timestamp: '2026-07-16T15:54:42Z'
citadel_version: 0.3.0
---

Beyond the beginner's green/black/oolong sketch, two variables explain nearly all of tea's diversity: how far the leaf is oxidised and whether that change is driven by the leaf's own enzymes or by microbes, and which cultivar of [Camellia sinensis](../objects/camellia-sinensis.md) the leaf came from — everything else, including colour, aroma, and the water used to brew it, follows from those two.[^s1]

Chinese tea tradition sorts true tea into six classes, best understood as a ladder of processing rather than a row of colours: all six come from the same species, and it is the maker's choices that produce the finished tea.[^s2]

**White** is the least handled class: the leaf is withered and dried with no deliberate kill-green step and no rolling, so only a little incidental oxidation creeps in during the long wither; silver-needle (buds only) and white-peony (bud plus leaves) are its classic styles.[^s3]

**Green** tea has its oxidation stopped early and hard: soon after picking the leaf is "fixed" (kill-green) with heat to denature polyphenol oxidase (PPO), the enzyme that would otherwise brown it. How the leaf is fixed splits the world's greens in two — China mostly pan-fires (as with Longjing/Dragon Well, wok-fired flat in Hangzhou), while Japan almost entirely steams (sencha, gyokuro), which locks in a greener, more marine, umami cup.[^s4]

**Yellow** is made like a green but with an added slow, damp "sealing" step (men huang, "sealing yellow"), in which the warm, just-fixed leaf rests under cover and mellows through gentle non-enzymatic yellowing, rounding out green tea's grassy edge into something softer and sweeter; Junshan Yinzhen and Meng Ding Huangya are its famous names, though the labour-heavy process makes the class nearly a museum piece today.[^s5]

**Oolong** is the partial-oxidation middle and the widest of the six classes: the leaf is withered, then bruised (shaken or tumbled so the edges break and oxidise while the centres stay green), oxidised anywhere from about 10% to 80%, then fixed and rolled — light oolongs sit near green and taste floral and creamy, while dark oolongs approach black and taste roasted and stone-fruity.[^s6]

**Black** tea — called "red tea" (hongcha) in China, after the colour of the liquor — is fully oxidised: withered, rolled to rupture every cell, oxidised right through, then dried, giving a dark, brisk, malty cup that forms the backbone of most Western breakfast blends.[^s7]

**Dark** tea (heicha) is post-fermented: after a kill-green step the leaf is deliberately aged under microbial action — bacteria and fungi, not the leaf's own enzymes, doing the work over months to years — producing an earthy, smooth, mellow tea that is often pressed into cakes, with pu-erh as its most famous example, detailed below.[^s8]

The distinction beginners most often miss is that black tea and dark tea are not the same thing: black tea is oxidised by the leaf's own enzymes in a matter of hours, while dark tea is fermented by microbes over months or years — two different chemistries that the word "fermented" often blurs together.[^s9]

## Sheng vs. shou pu-erh

Pu-erh, from Yunnan, is the dark tea most people actually buy, and it splits into two styles.[^s10] **Sheng ("raw") pu-erh** is kill-greened, sun-dried into loose "maocha," pressed into cakes, and then left to age slowly — years to decades — through gradual microbial and oxidative maturation; young sheng is bright, bitter, and almost green-tasting, while well-aged sheng turns deep, sweet, and mellow.[^s11] **Shou ("ripe") pu-erh** is the modern shortcut, developed in 1973 at the Kunming and Menghai tea factories to imitate decades of ageing in a matter of weeks: it uses wo dui ("wet piling"), heaping the leaf damp and warm for roughly 45-60 days so microbes force-ferment it, yielding a dark, smooth, earthy tea that is low in bitterness and drinkable immediately.[^s12] Same leaf, same province — one is aged for years, the other force-fermented in a pile, which is the single most useful thing to know about pu-erh.[^s13]

## See also
- [Tea](../objects/tea.md)
- [Camellia Sinensis](../objects/camellia-sinensis.md)
- [Tea Cultivars](tea-cultivars.md)
- [Tea Brewing](tea-brewing.md)
- [Tea Antioxidants](tea-antioxidants.md)

## Sources
[^s1]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 3-7 — the two variables (oxidation degree/mechanism, cultivar) behind tea's diversity (ingested 2026-07-16)
[^s2]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 11-13 — the six classes as a processing ladder, all one species (ingested 2026-07-16)
[^s3]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 15-19 — White class: withered and dried, silver-needle and white-peony (ingested 2026-07-16)
[^s4]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 20-25 — Green class: kill-green, PPO, pan-fire vs. steam (ingested 2026-07-16)
[^s5]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 26-31 — Yellow class: men huang sealing step (ingested 2026-07-16)
[^s6]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 32-37 — Oolong class: bruising, 10-80% oxidation range (ingested 2026-07-16)
[^s7]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 38-41 — Black class: full oxidation, hongcha (ingested 2026-07-16)
[^s8]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 42-46 — Dark class: post-fermentation, pu-erh (ingested 2026-07-16)
[^s9]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 48-51 — black vs. dark tea: enzymatic hours vs. microbial months-years (ingested 2026-07-16)
[^s10]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), line 55 — pu-erh from Yunnan splits into two styles (ingested 2026-07-16)
[^s11]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 57-61 — sheng pu-erh: maocha, ageing years to decades (ingested 2026-07-16)
[^s12]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 62-66 — shou pu-erh: 1973, Kunming/Menghai, wo dui wet piling 45-60 days (ingested 2026-07-16)
[^s13]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 68-70 — same leaf/province, aged vs. force-fermented (ingested 2026-07-16)
