The shou puerh that we can see in the market nowadays are all produced by using a process called "wet-pile fermentation (wo dui, 渥堆)." The stateowned tea producers in Yunnan have been producing shou puerh by this method since 1973, after they learned this craft from the Guangdong Tea Import and Export Co., Ltd.
Even though they were able to learn the techniques in Guangdong, the journey of Yunnan tea producers to perfect the craft of artificial fermentation can largely be described as a trial-and-error process, due to the unique temperature and moisture levels in Yunnan. Through numerous experiments, tea producers finally made the necessary adjustments and were able to produce artificially fermented puerh of a high quality. Nowadays, shou puerh is widely considered a more affordable version of puerh tea, and it plays an important role in supplying enough puerh teas to satisfy the market.
You would probably like to know whether the "wet-pile fermentation" that we discussed earlier was the first artificial fermentation process to be tested in Yunnan. While I don't have a definite answer, my guess is that it was not. I believe that the tea producers in Yunnan had done a lot of unsuccessful experiments on producing shou teas, before they went to Guangdong to learn the craft in 1973. Maybe the other methods that the tea producers tested were less cost-effective, or those methods would make it difficult to maintain product quality and stability.
What we can be sure of is that the tea producers in Yunnan failed to find a way of mass-producing shou teas, and that's why they went to Guangdong in search of a new path. Thus, even though the wet-pile fermentation method may not be the best fermentation method in terms of quality or mouthfeel, it is naturally the best way for tea producers to mass-produce shou teas with low cost, high quality and stability.
There were articles written to record the fermentation process of puerh that had taken place in Yunnan prior to the 1970s. The following paragraph about the history of the fermentation process in the 1930s is excerpted from the article "A brief summary of the tea industry in Menghai," written by tea expert Li Fuyi in 1939:
"(The tea leaves) would be piled, in order to make wet-pile tea. After one day's time, the wet-piled tea would then be fermented for a second time. As the moisture level of the leaves was still quite high, the tea would be fermented for a third time. Some yellow mold would then begin to grow on the tea leaves. Some tea lovers would then describe the teas to be in perfect condition."According to A Book of Puerh Tea, the Menghai Tea Factory used a fermentation process called "steaming fermentation" to produce shou teas. Also, according to Cao Zhenxing, who was a plant manager of the Menghai Tea Factory, they had been experimenting with the post-fermentation of puerh teas since 1969. They originally planned to mass-produce those teas for Tibetan consumption, but abandoned that idea due to the lack of success with the fermentation techniques at that time. On the other hand, the steaming fermentation method was also adopted in producing a tea called "Yunnan Qing," which was sold to Hong Kong. It proved that the state-owned tea producers in Yunnan had been producing shou teas before learning the wet-pile fermentation process in Guangdong.
In a memo from the Xiaguan Tea Factory, it was written that Yunnan ceased the production of round-shaped tea cakes during the Cultural Revolution (1966 - 1976), to concentrate on the production of Seven Sons Cakes (Yunnan Chi Tse Beeng Cha, 雲南七子 餅茶). These tea cakes were classified into sheng and shou cakes. In making these cakes, the maocha was first mixed before going through a series of processes, including sorting, selecting, steaming and shaping.
After studying these historical records, we know that the artificial fermentation process of shou puerh teas has a long history. The quality and mouthfeel of a shou puerh largely depends on controlling the temperature and moisture levels, as well as the environment of the fermentation plant. Thus, how the tea producers ferment shou puerh is, ultimately, decided by the market, as the taste of end consumers changes throughout time, and an experienced market means better tea.
Wet-pile fermentation has been adopted by Yunnan tea producers since 1973, after a long period of learning, experimenting and adjusting. This fermentation process is not an innovation of Yunnan. Instead, it is a reliable process for artificial fermentation of puerh teas, and it was, indeed, a breakthrough for the tea production industry in Yunnan.
To know more about Yunnan puerh tea, we should learn more about the years 1973 to 1975, as the standard recipes were developed in this period. 1975 was an especially important year for puerh tea, as it marked the beginning of standardized production of puerh tea. As of that year, methods of mixing tea leaves were standardized, and the names that we all know today (such as 7542, 7532, 7452 and 7572) were brought into the world.
We can easily see that the standardized production process created a path for mass production of standardized puerh teas, especially shou puerh, by adopting the wet-pile fermentation process. This was how the shou puerh that we see today were initially invented.
Actually, some of the earliest products produced by the Menghai Tea Factory had a different style from those wet-pile fermented teas. For example, this year, I tried two cakes produced by them. Both of the cakes have traditional Chinese characters on them. One of the tea cakes is an "iron discuss (tie bing, 鐵餅)," while the other one is a Yellow Mark (黃印) cake.
Both of the teas that I mentioned above are shou puerh teas. Li Yisheng, who was the vice general plant manager of the factory, told me both of the products were produced during the 1960s, even though there was no wrapping paper to indicate this fact. In my book, Profound World of Chi Tse, the original packaging of the two cakes was presented. Both of the cakes are shou teas, instead of sheng teas, and they have a significantly different style from the wet-pile fermentation teas produced after 1975.
I believe that those tea cakes had a style similar to the "Yunnan Qing" mentioned by Cao Zhenxing, and their unique taste is different from 7572 tea cakes, 7452 tea cakes and Jinggu bricks. In the following section, we are going to discuss the characteristics of the two cakes that I mentioned earlier.
Firstly, the name of the company, as printed on the packaging, is "Yunnan Branch China Tea Import and Export Co., Ltd." instead of "China National Native Produce & Animal By-Products Import & Export Corp.," which proves that the tea cakes were produced before 1971. Thus, we can see that tea companies in Yunnan had already been producing artificially-fermented puerh teas before adopting the method they use today. Secondly, the brewed leaves are not so dark and carbonized, which is very different from the tea leaves processed by the wo dui process.
The fermentation style of these products is vastly different from those standardized products produced since 1975. If you've seen these cakes, you may have already noted that the name "China National Native Produce & Animal By-Products Import & Export Corp." was printed on the packaging of the teas, but not on the inner trademark ticket (nei fei, 內飛). This is because the name of the seller was printed on the packaging, while the name of the producer was printed on the nei fei. Thus, changes in packaging solely reflected changes in the structure of the state-owned company, which has nothing to do with the tea producers, as long as the state-owned company still used their existing products. (Note that the wrapping papers were designed and produced by the stateowned company.)
Amongst these teas, "Yellow Mark" with traditional characters, "Big Yellow Mark (大黃印)" and "Big Blue Mark (大藍印)" all have a similar style, and the diameter of those tea cakes is wider than a common Seven Sons Cake. Thus, we can see that these tea cakes were produced roughly around the same period. You can also verify this fact by seeing the packaging yourself.
As the production facilities and techniques kept improving, the tea producers could control the wet-pile fermentation process pretty well. However, the problems of underfermentation or over-fermentation still existed. In addition, the temperature in the center part of the tea during the wo dui process would often be quite high, which would sometimes make the tea partially carbonized. However, even though these factors would make the taste and mouthfeel of each tea cake unique, so this fermentation process is still considered the most stable for mass production.
As I mentioned earlier, the craft of artificial fermentation is built upon experiments and experience instead of imagination, and there is no shortcut to success. Despite the fact that the Yunnan tea producers learned a lot from the Guangdong tea producers, they still needed to make the necessary adjustments using their own experience.
As we would all agree, the shou teas produced by the Menghai Tea Factory have a different style and taste from those produced by the state-owned company in Guangdong. This is because the Menghai Tea Factory was actually improving its existing fermentation process for mass production after learning in Guangdong, instead of copying the whole process from other tea producers.
After 1975, artificially fermented teas were produced on a large scale. Compared to the teas produced during the experimental period, the teas produced after 1975 were more cost-effective and more stable in quality. Even though these teas do not taste significantly better than the teas produced before 1975, the tea producers could make more profit by producing teas on a larger scale. Thus, the development of shou tea production that we have witnessed is reasonable and logical.
As the tea leaves are often damaged or carbonized during a heavy artificial fermentation, the mouthfeel of such shou tea is not as strong as sheng tea, and that is why many tea drinkers belittle shou tea. However, I still believe that shou tea plays an important role in the puerh world, as it can be produced on a large scale and be consumed right after it leaves the factory. Also, many aged shou teas are much cheaper than the sheng teas of the same age! After all, aged tea being sold at a discount is irresistible, wouldn't you agree?