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Aging Pu-erh tea: wet storage vs. dry storage (Part II)

Posted by Boyka Mihaylova on

Following up from the Part 1 of our "Aging Pu-erh tea: wet storage vs. dry storage" exploration, here’s the second part of our blog post, dedicated to storing and aging Pu-erh tea. We talk about the phase of transitioning from wet to dry Pu-erh. We explore the advantages of dry over wet storage and give an answer on 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 the storage. Finally, you will learn the best ways to store tea at home, depending on its shape and quantity. Let’s dive in!

  

Aging Pu-erh: from wet to dry storage – the transitioning 

Back in the days, the usual practice for Pu-erh tea was to travel from Yunnan to Hong Kong. Along the way, the tea fermented naturally under weather conditions. Then, it was stored in Hong Kong. The hot and humid climate there accelerated the rapid aging of Pu-erh tea. On the contrary, Kunming is much drier, with an average air humidity of 70% and below. People discovered that storing tea in high-altitude warehouses in dry climates results in excellent quality. This gave birth to the concept of dry storage. It gradually gained popularity and became the leading practice in Pu-erh tea storing and aging.

 

What is dry storage, and how does it influence Pu-erh quality?

Dry storage refers to storing tea leaves in a clean and dry place at a moderate temperature. Some argue that the best temperature is within the 70-75% range, while others admit it should be below 80%. The ventilated space allows the tea leaves to transform and age slowly and naturally.

 

Can dry storage take place in hot and humid areas?

Yes. Much like wet storage, dry storage can also take advantage of the natural conditions of the region. Kunming is an example of an area with natural dry storage. This also applies to the northern parts of China, e.i. Beijing. However, dry storage can happen in places like Hong Kong, Guangdong, etc. These are professional warehouses with strict air permeability, humidity, and temperature control.

 

Aging Pu-erh: dry storage advantages

Since its introduction, dry storage has quickly replaced wet storage due to the excellent results it produces. Some of the benefits of dry stored tea include:

  • Development of “aged aroma” (Chen Xiang – 陈香), prized by tea lovers and collectors
  • Strong, long-lasting aroma, far superior to wet storage teas
  • Clean and fresh appearance, bright and transparent tea soup
  • Pure and intensive taste, naturally mellow mouthfeel
  • Lack of harmful/ pathogenic microflora
  • High resistance to brewing

 

While excessive moisture in wet storage promotes quick and heavy fermentation, dry storage encourages a transformation of the tea leaves through the activity of the internal enzymes in the tea leaves. The action of the enzymes happens naturally; thus, the tea ages slower.

 

pu-erh tea mold

green mold on improperly stored pu-erh tea  

 

What about wet storage – is it good or bad for aging Pu-erh?

It’s worth noting that wet storage in itself is not necessarily a bad thing. Bacteria are vital for a good transformation of the tea leaves. Without them, the tea will simply not evolve. This means that if we leave the tea without any moisture whatsoever, it will just get old and eventually will fade out. Therefore, storing tea in a naturally humid environment has been widespread for decades. Places like Guangdong, Hong Kong, Taiwan, etc., benefit from their increased moisture that develops a specific regional flavor for their teas.

 

So how to ensure you're effectively storing and aging Pu-erh tea? 

Two essentials:

  1. Control Oxidation
  2. Stabilize moisture

 

The key to effectively aging pu-erh - tea moisture content

If the water content is too low, it will lead to a lack of living conditions for microorganisms. The tea will stop transforming and will gradually lose its taste, flavor, and aroma. If it is too high, it will cause an outbreak of harmful bacteria.

 

What moisture content will make the transformation most efficient?

Standard pressed tea leaves roughly contain 10% moisture when it leaves the factory.

If the water content of tea leaves is higher than 14%, it is very easy to breed bacteria; the tea leaves become moldy, and the stored tea will have a "wet warehouse" smell.

When the moisture content of tea leaves is lower than 7%, the growth of microorganisms basically stops – thus, the fermentation halts too. If the storage continues under such circumstances, the tea will only age by oxidation and will eventually fade out.

 

Does the tea shape influence the storage?

In short, yes.

The ideal form of storing tea is pressing it. Tightly pressed shapes reduce external oxidation and retain moisture.

 Let’s see how various forms influence storing and aging Pu-erh.

 

  • “Iron” tea cake (Tie Bing – 铁饼)

This is a Pu-erh tea cake directly pressed with a metal mold. The high mechanical pressure ensures very tight pressing of the tea leaves, making the cake hard as iron, hence the name. 

When making Iron tea cake, workers directly put the dried tea into a metal container to steam and soften it. They then press the leaves into the container with a metal mold. The iron cake is harder than ordinary tea cakes, and it is not easy to pry open. This ensures a stable, non-leaky environment. Experienced tea drinkers generally agree that old cakes taste best.

 

The bricks can also be pressed very tightly. In addition, stacking them reduces air circulation.

 

This is the most mainstream form of pressed tea. The transformation is comparable to the iron cake, but the leaves remain intact. It is also more convenient to pry open.

 

Loose tea is particularly prone to oxidation, especially if stored in a ventilated environment. It is convenient for daily usage but not recommended for long-term storage.

Other shapes, such as Tuocha, also depend on their degree of compression.

 

pu-erh tea shapes

  

What’s the best way for storing and aging Pu-erh tea at home?

Tea circles frequently discuss the dry and wet storage subjects. The general climate conditions in a particular region are without a doubt essential for the proper storage and aging of tea. However, when packing the tea, we create sort of a microenvironment inside the packaging. This microenvironment is of no less significance for preserving and enhancing the tea as time goes by. In fact, the influence of the external environment on the microenvironment of tea is indirect. The main task is to isolate the tea properly in its microenvironment. This way, we will be able to control oxidation and moisture and maintain their levels stable. Therefore, by choosing a suitable packaging, we can ensure proper storage and aging for the tea as time goes by.

 

To seal or not to seal

Sealing is a frequent subject of discussion regarding tea storage. The Northern hemisphere, where most of the western world is, is much colder and drier than China and South-Eastern Asia in general. Therefore, storing recommendations can vary greatly. Sometimes they can even be misleading if not interpreted according to the specific region. For the sake of discussion, we will accept that the main goal of the storage and aging process is to maintain stable levels of oxidation and moisture, per the references quoted above.

 

  • Single tea cakes are suitable to keep in their original packings, consisting of a cardboard box and a thin plastic bag, usually made of cellophane.

Some people advocate putting the cake in a zip lock bag. This is a good solution in case you live in particularly wet, or the opposite, excessively dry surroundings. It will ensure constant and stable levels of moisture and oxidation for the tea, preventing it from either overdrying or molding.

 

Others go as far as vacuum-sealing the cake. Proponents of the latter method claim that aging mostly doesn’t require external oxidation and instead occurs through fermentation and internal enzyme activity. Some insights state that this way of storage lets aroma and aftertaste evolve. However, the lack of external oxidation retains the astringency in the tea soup.

 

  • A glazed porcelain jar or a tin can are good storage solutions for a smaller amount of tea. Keep in mind that a purple sand (zisha 紫砂) jar is breathable and water-permeable. It is therefore not conducive to long-term storage. However, it is a great tool to wake up tea before brewing.

 

  • Bamboo leaf wrap and carton is a usual package of choice for bigger quantities like cha ti (茶提, a pack of five, seven or more cakes). They isolate well and maintain a relatively stable

 

Some people recommend sealing the carton gaps with sealing tape for added protection from moisture and airflow. It is best to use a coated waterproof carton in very humid areas. Another solution is to add a dehumidifier pack inside.

Alternatively, people in extra dry climates use special devices like pumidors to maintain sufficient moisture. There are tea versions too, called pumidors. A pumidor is basically a storage container for aging Pu-erh tea at controlled temperatures and humidity. Normal wooden or plastic cabinets are also a popular solution. One of the shortcomings here is the increased air permeability. Also, frequent opening of the doors will cause an airflow, that might influence the aging process, especially the accumulation of aroma.

 

  • Sealing is the best solution for loose Pu-erh tea. Vacuum sealing will prevent it from over oxidizing and fading.

 

Little things to watch for when storing and aging Pu-erh tea

  • Don't put tea in a place where the temperature difference varies greatly 

For example, a cold wall in an otherwise warm environment may condense. Putting the tea next to this wall may cause molding.

 

  • Watch out for unwanted odors in or near the tea storage space

Tea easily absorbs smells. Keep it away from any strong-smelling substances. This includes smelly food in the fridge, where lots of people keep their green teas.

 

  • Keep away from direct sunlight

Ultraviolet rays can destroy tea within hours.