Home-Aged Pu'er

Between Permeability and Impenetrability

Pu'er Tea is characterized by its ability to improve with age. How to store Pu'er tea properly at home is a topic of interest for many tea enthusiasts. There are various containers for storing tea, each with its own advantages and disadvantages. In my opinion, the breathability of the container plays a significant role in determining the storage outcome. From practical experience, the key to storing Pu'er tea lies in achieving a balance between permeability and impermeability; too much breathability can cause the tea to lose its aroma, while too little can result in unpleasant sourness.

The breathability of common storage containers available on the market varies. Metal containers, high-temperature porcelain, glazed high-temperature Pottery, and plastic bags are generally impermeable. On the other hand, Yixing clay jars, low-fired low-mesh earthenware jars, and bamboo baskets are too permeable. However, Zisha (purple clay) jars from Jian Shui, which are high-mesh high-temperature pottery, have moderate breathability, striking a balance between permeability and impermeability.

The breathability of ceramics is related to the mesh size of the clay used and the firing temperature. “Mesh size” is a measure of the coarseness of the clay, defined as the number of sieve holes per square inch. A larger number of sieve holes means a higher mesh size and finer clay. For example, Yixing clay typically has a mesh size of 40-80, making it coarse and sandy, with a firing temperature of 1100-1200°C; zisha clay usually has a mesh size of 200-300 (up to 400 in some cases), making it finer, with a firing temperature of 1100-1250°C.

The lower the mesh size of the clay, the rougher it is, and the more permeable the finished product becomes; conversely, a higher mesh size results in finer clay that is less permeable. Yixing clay has a very low mesh size and rough pores, allowing strong breathability; Zisha clay, with a higher mesh size and finer texture, has moderate breathability. Historically, Pu'er tea was not stored as loose leaves because this would cause the aroma and flavor to dissipate quickly. Instead, it was compressed into shapes like “tea cakes,” “golden melon tribute tea,” and brick or nest teas, often wrapped in bamboo sheathes, which helped retain the aroma and flavor. This method also facilitated transportation and ensured the quality of the tea.

The traditional “bamboo sheath wrapping” can be considered a significant invention in tea storage. Industry insiders who understand the process tend to choose bamboo sheath wrapping when storing large quantities of tea, then sealing it in cardboard boxes. The bamboo sheathes help isolate the tea from the air, retaining its aroma and flavor, while still allowing some air exchange. After compressing the tea into shape and wrapping it in bamboo sheathes, the aim is to reduce the permeability, placing the tea between permeability and impermeability, thus better preserving its flavor and aroma. When tea is well-stored, opening the bamboo sheath reveals an enticing aroma.

In modern times, when collecting Pu'er tea, two main considerations should be taken into account: drinking value and collection value. We need to ensure the tea tastes good and maintains high quality, preserving its aroma and flavor as much as possible, while also considering whether the storage conditions are conducive to the tea's maturation and quality enhancement, thereby increasing its drinking and collection value. When collecting Pu'er tea, two key factors must be considered: constant temperature and constant humidity within a certain range.

A constant temperature is beneficial for the fermentation of the tea. Generally, a temperature around 20-30°C is ideal. If the temperature fluctuates greatly or is too high, the fermentation process will accelerate, resulting in a sour taste. Another important factor is maintaining constant humidity within a specific range.

Good Pu'er tea requires “dry storage,” meaning it should be kept in a dry environment, avoiding moisture. When the humidity exceeds 75% and the moisture content goes above 14%, the tea cakes can easily mold. However, the environment cannot be too dry either; when the moisture content drops below 7%, microbial activity diminishes, so there needs to be a certain level of breathability and humidity.

Besides the small environment (internal environment) inside the container or packaging, there is also the larger external environment. The internal environment refers to the conditions within the container or packaging, while the external environment encompasses the surroundings outside these containers. Changes in the external environment's temperature and humidity can affect the internal environment, and different containers can react differently to these changes. For instance, storing tea in a Yixing jar may work fine in a dry place like Kunming but could cause problems in a humid area like Guangdong.

I have seen various methods of storing tea. To enhance the drinking value, some people store tea in impermeable containers such as tin cans, porcelain jars, or glass jars to lock in the aroma and flavor, or even in vacuum-sealed conditions. While this approach temporarily preserves the aroma and flavor, it compromises the long-term collection value of the tea. Pu'er tea requires a certain amount of oxygen during storage for the polyphenols and active enzymes to undergo oxidation reactions, promoting the growth of beneficial bacteria and facilitating the transformation of the tea.

Considering both drinking and collection values, the Zisha jars from Jian Shui are an ideal choice for home storage of Pu'er tea. In the test report titled “Comparison Experiment on the Relative Constant Temperature and Humidity of Purple Clay Tea Cylinders,” testers placed hygrometers inside and outside a Zisha jar to observe the differences in temperature and humidity over a day. The data showed that when the external humidity fluctuated between 28% and 86% over 24 hours, the humidity inside the jar remained consistently between 66% and 68%. This indicates that Zisha jars provide a constant temperature and humidity, shielding the tea from excessive heat and humidity. They prevent the tea from molding during the rainy season and avoid overheating, which can lead to a sour taste. Therefore, the moderate breathability of Zisha jars from Jian Shui, between permeability and impermeability, is highly beneficial for storing Pu'er tea, preserving its aroma and flavor while providing suitable conditions for its transformation over time.

When using Zisha containers to store Pu'er tea, three types of jars are commonly chosen. The first type is called a “carrier jar,” designed to hold one, two, or three carriers of tea cakes that are not convenient to put back in bamboo sheathes. The second type is a “cake jar,” also known as a tea waking jar, suitable for storing one cake of tea. Before brewing, break up the Compressed tea into chunks and let it rest in the jar for a period of time; this enhances the flavor. Place the jar in a slightly warmer area and uncover it to smell the aroma, indicating it's ready for brewing. The third type is a “brewing jar,” also known as a tea tasting jar, capable of holding several grams of tea for a few brews, making it convenient for travel and ensuring the tea does not absorb unwanted odors in the car.

And mobilizing the public to participate in environmental protection efforts, through green and low-carbon lifestyles, to improve the overall environment of the Earth.

Originally published in Pu'er Magazine

November 2025 Issue

Author | Shi Tao Images | Ruan Weiming [except where credited]

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