Pu-erh is among the most fascinating and controversial topics in the world of tea. Today, we will discuss a major aspect of the Pu-erh tea production cycle: aging, or storage. There are two primary schools of thought: wet storage and dry storage. Let's explore their differences and the way they affect Pu-erh tea quality.
What is Pu-erh tea?
Pu-erh tea is a fermented tea common in China. According to the National standard, it has a Protected designation of origin (PDO). That means only tea grown and produced in Yunnan province can go by the name of Pu-erh. However, similar sun-dried dark teas are traditionally produced in neighboring regions such as Northern Vietnam, Laos, Myanmar, and Thailand – these teas are usually called Sun-Dried Tea. This tea has a history of more than 1000 years. Pu-erh tea, as we know it today, appeared during the Ming dynasty (1368 – 1644). However, people in Yunnan cultivated tea as early as the Eastern Han dynasty (202 BC – 220 AD). Later, during the Tang dynasty (618 – 907 AD), they began trading with it along the borders of the empire, leading to the creation of the Ancient Horse and Tea Road.
What are the differences between Pu-erh tea variations?
Pu-erh tea exists in two variations. As with other major tea types, the main difference lies in the production process.
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Raw Pu-erh (Sheng Pu-erh – 生普) is a variety made from the fresh leaves of the Big Leaf variety (Da Ye Zhong – 大叶种) of Camellia Sinensis. The traditional processing method includes several stages. First, farmers pick the leaves and leave them in the shade to wither. They then pan-fire them to halt the oxidation. After that, they roll the leaves to get rid of excessive moisture. Finally, they dry them in the sun. The result is a semi-processed loose tea called maocha, which workers then steam and press into Raw Pu-erh cakes.
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In a nutshell, Ripe or cooked Pu-erh (Shu Pu-erh – 熟普) is Sheng Pu that undergoes microbial fermentation. It occurs during a processing stage called "wet piling", or Wo Dui (渥堆). That is done by piling a large amount of maocha and sprinkling it with water. Increasing humidity and temperature give rise to a unique microflora of molds and bacteria that begin to ferment the leaves. After a certain period (usually 40 to 60 days), the workers unpile and ventilate the tea. They then press it into various forms, including cakes and bricks.
What is aging, and how does it affect Pu-erh tea?
Aging is the last step in the Pu-erh production cycle. It is also a key component of the end product's quality, along with the raw material and production process. We need to understand what happens to tea during storage to grasp its importance.
Post-fermentation explained
Pu-erh belongs to the category of post-fermenting teas. This process includes three factors:
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Internal oxidation (aka endo-oxidation): the transformation of the tea under the influence of enzymes inside the leaves. Although most enzymes have been deactivated during the Killing green stage, some of them remain alive. With time, they continue to transform the leaves from the inside. That is the slowest part of the process.
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External oxidation (aka exo-oxidation): This refers to oxygen coming into contact with the tea leaves. It's a quicker process than endo-oxidation. It's also one that needs to be monitored and controlled. Excessive oxidation will deplete the leaves of aroma and flavor, making the tea dull and bland.
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Fermentation: This is the effect that some bacteria and mold produce on the tea leaves. Their activity transforms the tea taste, aroma, and mouthfeel. The bacteria require a certain amount of water (humidity) to develop. If the moisture level is too low, there will be no microbial development; if it's too high, it will lead to the growth of harmful, toxic microflora.
The storage and aging of Pu-erh tea result from the combined effects of some or all of the above processes on tea leaves over time.
Over time, two main styles of storing and aging Pu-erh tea emerged: wet storage (Shi Cang, 湿仓) and dry storage (Gan Cang, 干仓). Let's explore how both affect the Pu-erh tea quality.
What is wet storage, and how does it influence Pu-erh tea quality?
Wet storage refers to storing tea leaves in a humid environment, often at elevated temperatures. High moisture causes explosive growth of mold and bacteria. In turn, this shortens the storage time. Wet storage accelerates the tea's aging. However, it also hides some hazards.
• Aging Pu-erh tea: natural wet storage
It's worth noting that when we speak of wet storage, it can refer to both natural climate conditions and artificially controlled ones. Some wet storage representative areas include Hong Kong, Guangdong, and Taiwan. The average air humidity in all of these places exceeds 80% during most of the year. Storing the tea there lets it experience a naturally humid environment and its effects. We call this kind of storage natural wet storage.
• Aging Pu-erh tea: artificial wet storage
Wet storage can also refer to storing the tea in an environment with artificially elevated moisture. The high humidity forces the tea to quickly "ripen". That way, it becomes profitable and could be sold more quickly than if it were left to age normally.
Transformation is a major advantage of Pu-erh tea. It defines its market value and quality range. To achieve a good transformation, we need a combination of controlled oxidation and fermentation to occur in tea leaves. Both of these processes happen with wet and dry storage. However, the outcome is quite different.
• Wet storage advantages
Fermentation is part of the aging process. It is a result of the activity of microorganisms, which need water to develop and thrive. Elevated moisture in wet storage causes surges in mold and bacteria, enhancing the tea leaves' fermentation. Some of the good effects of wet storage include:
- Notable shortening of the time required for aging the tea
- Sweet taste
- Lubricated, "oily" mouthfeel of the tea soup
- Development of a specific "wet" flavor, prized by some tea lovers & collectors
- Rich microflora
However, this is where it gets complicated.
•Wet storage shortcomings
Too much of a good thing is not necessarily a good thing. An example of such practice is the Hong Kong tea market in the 90s. Back in time, there was a growing demand for tea with a mellower taste and an "aged" flavor. That applied both to the inland market and to Hong Kong, Taiwan, and some countries in Southeast Asia, such as Malaysia. Hong Kong was a major tea hub, catering to both the inland and the overseas markets. However, space in Hong Kong was (as it is today) notoriously scarce and therefore expensive. Lots of tea merchants couldn't afford to build or use professional warehouses. They then stacked their teas in port cabins, in damp and stuffed spaces (some people believe that's when the "fishy smell" notion appeared), or in low-rent underground warehouses.
Increased moisture and lack of ventilation caused more harm than good in tea leaves. It took years to notice the adverse effects of the wet storage, some of which include:
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Formation of peculiar smells (i.e., heave warehouse smell, fishy smell, musty smell, earthly smell, and so on)
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Harmful bacteria outbreak
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Formation of carcinogenic substances as byproducts of some microorganisms' activity
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Tea molding, musting, or rotting
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Lower quality - heavy, unpleasant taste; loss of aroma; muddy, turbid tea soup
88 Qing Bing and the birth of dry storage
Things changed with the now-legendary story of the "88 Qing Bing" (八八青饼). In 1993, Chen Qiang, a sales representative for Menghai Tea Factory, offered Hong Kong tea merchant Chen Guo Yi (陳國義), aka Vesper Chan, an entire 30-ton batch of raw Pu-erh – tea that had been produced between 1989 and 1991 using the 7542 recipe, but had not sold well, since most Hong Kong tea drinkers at the time preferred ripe or well-aged Pu-erh and considered young raw Pu-erh too bitter and astringent.
After tasting a sample, Chan was impressed by the tea's quality and decided to buy the entire batch despite the storage and marketing challenge it presented. Rather than following the conventional Hong Kong practice of the time – storing pu-erh in deliberately humid, even damp conditions to speed up aging – Chan chose to store the tea dry, a far less common approach in Hong Kong at the time. Aged this way over the following decades carefully, the tea developed a remarkably clean, complex character that set it apart from the heavier, mustier profile typical of conventionally wet-stored teas of the era. The batch became known as "88 Qing Bing" and went on to become one of the most celebrated and valuable Pu-erh cakes in modern collecting history. In 2020, two bings from this batch sold at auction for 1.725 million yuan (about $250,000).
More than 30 years after the initial purchase, the tea remains moist and oily, sweet and long-lasting, according to tea lovers, lucky to taste it.
That is arguably the most successful investment in the history of Pu'er tea. Since then, "88 Qing" has earned the reputation of "founder of dry storage". Read more about "88 Qing Bing"
That's all for today! Next week, in the second part of this article, we will discuss the phase of transitioning from wet to dry storage. We will then explore their advantages and shortcomings and answer whether wet storage is good or bad after all. You will learn the two essential factors that guarantee effective storage for your tea cakes. You will also understand how the shape influences tea storage. Finally, you will learn the best ways to store and age Pu-erh at home, depending on its shape and quantity. Stay tuned!
