1. What is Dark Tea?
Dark tea (chin. “hei cha”) is a post-fermenting green tea of large-leaved tea tree varieties (“Assamica” varieties) in Yunnan and neighboring regions. Accordingly, the method of processing dark tea is common wherever large-leaved tea tree varieties are native: Yunnan, Sichuan, Guizhou, Guangxi, aber auch Nordvietnam, Myanmar, north Thailand and Laos. A nice example of a particularly individual such sub-variety is the north Vietnam native “Tuyet Shan” tea tree.
The method of processing dark tea is as old as that of processing green tea. For both, there is literary evidence in China starting from the late Tang dynasty (618- 907). At this, the two processing methods initially appear to be similar except of two features:
- first, it must be leaves of large-leaved tea tree varieties for dark tea;
- second, dark tea must drys outdoors in the sun after processing
As opposed to this, most green teas come from small-leaved tea bush varieties. Also, their final drying relies on heat feed, this usually taking place inside the tea factory.
It is important to know that dark tea, just like green tea, is not oxidized. Much rather, the ripening processes taking place after the tea’s initial processing are indeed fermentation processes. This means, as opposed to the oxidation of tea leaves, there are no enzymatic reactions occurring with the ripening of dark tea. Instead, the fermentation consists of comparably time-consuming microbial reaction processes.
2. What is Pu Erh Tea?
Yunnan considers itself as the place of origin and center of dark tea processing. This refers in particular to the prefectures of Xishuangbanna, Pu Erh (formerly: Simao), Lincang and Baoshan, but also other Yunnan prefectures. At this, the “Six Great Tea Mountains” in Xishuangbanna on the east bank of the Mekong are of historical importance: Gedeng Shan, Yiwu Shan, Mangzhi Shan, Manzhuan Shan, Yibang Shan and Yōulè Shan. Meanwhile, the term “Pu Erh Tea” is protected as a term for dark teas coming from Yunnan.
Whether mountain tribes in the surrounding home countries of the tea tree might have produced dark tea from their native large-leaf tea tree varieties as early as this, too, or not, blurs in the fog of time. In turn, there’s historical evidence that since about the turn of the millennium tea from Pu Erh traveled on the Ancient Tea-Horse Road from Yunnan to Lhasa – and from there to Europe, among others.
3. Dark Tea (Hei Cha) / Pu Erh Tea Processing
Except for the leaf material coming from large-leaved tea plant varieties and sun drying, the initial processing steps of dark tea are similar to those of green tea processing. For a step-by-step depiction of this processing sequence, please (re-)consult Lesson 8.3. – Green Tea Processing.
With dark or pu erh tea processing, the result of this processing sequence is the so-called “Maocha“. In the old times, this Maocha was then pressed into cake or brick shape and then left to natural ripening processes. On the one hand, the pressed shape was conducive to the transportability of the tea on mule backs over long distances. On the other hand, it probably influences the ripening process. Nevertheless, you can also find loose dark teas.
3.1. “sheng” cha and “shou” cha
Decades go passing by before the pressed or loose Maocha has naturally matured into a fully fermented dark tea. During this time the appearance and taste of the tea change continuously. The original green of the leaf changes to an ever darker brown. At the same time, the cup color turns from light yellow to dark yellow, orange and brown to almost black. We refer to such naturally maturing dark tea as “sheng cha”.
It was only in the early 1970s that researchers in Yunnan developed a method (渥堆, wò duī – “wet pile”) for drastically accelerating – or rather mimicking – the natural ripening process. The new methode enabled achieving a taste result in just weeks, for which the tea so far had to mature for decades. We refer to the “ripened” dark tea resulting from this method as “shou cha”.
3.2. Shou Cha Ripening
To accelerate the ripening of a shou cha, the maocha is piled up while moistening in a hot room in a thick layer and then covered. Under such conditions, the fermentation process soon sets in. During the following weeks, the producer will uncover the tea from time to time, to regulate moisture and heat. At this, the repeated turning of the tea leaves ensures the even distribution of heat, moisture and bacteria in the pile. Finally, the originally yellow-green tea leaves take on a continuously reddish-brown color. Then they are left to ripen for another while in favor of a mild, harmonious taste. After final drying, they might be pressed into one of the characteristic shapes – or left loose.
3.3 Vintage Pu Erh / Dark Teas
As with other tea categories, different types of dark tea or pu erh tea first of all arise from characteristics such as origin, terroir, (sub) variety, cultivation style and picking standard. However, while all other teas are fresh at their best, the quality and value of a dark tea grow with the years of maturing. This applies in particular to naturally maturing “sheng”. That is why many producers store their naturally maturing dark teas from year to year, in order to offer them as “vintage teas”. This applies in particular to the long-established, famous pu erh tea factories in Yunnan’s classic regions of origin.
In this way, dark teas or Pu Erh teas also provide an investment opportunity with a safe and high return on investment. If you want to invest here, make sure there’s proper documentation of your purchased tea’s origin and vintage. In addition, it is, of course, advisable to ensure proper storage, i.e. as dry as possible and at not too high temperatures.
One more thing, on my own account…
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