How To Store And Age Pu-erh Tea

In 2019, 2.2 kilograms of raw pu-erh tea made in the 1920s sold at a record breaking auction in Hong Kong for US$3,362,774 — approximately US$4,132,488.14 in today’s dollars.

Why did a nearly 100 year old tea fetch such a high price? Because of storage.

One of the fundamental drivers of interest and investment in pu-erh tea is the idea that you can deliberately refine a pu-erh tea’s aroma, flavour, and other characteristics through careful longterm storage. 

In this article, we explore what pu-erh storage accomplishes, why it matters, and how to do it at home.

An Introduction to Pu-erh

At first glance, fresh raw pu-erh tea looks a lot like green tea — this is somewhat unsurprising given that both teas are processed in a similar manner. When brewed, both raw pu-erh and green tea offer the drinker plenty of astringency, savouriness, and bitterness. However, as anyone who has bought green tea knows — there’s an expiry date on the tea’s unique characteristics. With time, green tea’s fresh aroma and vaguely herbaceous flavour will stale, yielding a far less fragrant and flavourful tea. In short, no one’s buying an old green tea for millions of dollars.

So, given the similarities between pu-erh and green tea… why would anyone pay exorbitant prices for old raw pu-erh cake?

The key to answering this is twofold.

The first part involves unpacking the critical differences between how pu-erh teas and green teas are made. We explore the topic of pu-erh production in our earlier articles — How Puerh Tea is Made Part 1 and Part 2.

The second part lies in understanding pu-erh storage: what its purpose is, what’s involved in effective storage, and how to do it yourself.

The Purpose of Storing Pu-erh Tea

The overall point of pu-erh tea storage is to enhance or transform the tea’s characteristics to their optimum state through a deliberate cultivation of microbial activity.

If you read our earlier articles on processing, you might recall that pu-erh tea is alive — well, sort of.

Unlike green tea, pu-erh tea production allows for small quantities of organic compounds to survive in the tea leaves. The purpose of storage then is to take advantage of this unique characteristic in order to manipulate and transform pu-erh tea’s flavour, aroma, and overall effect on the body.

When raw pu-erh tea is stored in a suitable environment (more on this in a second), its leaves undergo a series of complex microbial changes that transform the tea’s overall profile. If you appropriately store a recently made raw pu-erh for a few years, you can expect the tea to transform from green-hued, fresh and harsh, to dark brown hued, aged and smooth. This microbial process is much like maturing spirits in a cask to create whisky.

Given enough time, all storage will accomplish some kind of transformation in pu-erh tea. On one end of the spectrum, raw pu-erh tea that is stored in an extremely hot and humid environment will change very rapidly. After a few years of hot and humid storage, what was once fresh raw pu-erh will look and taste more like ripe pu-erh — smooth, fermented, and very dark. If the storage is particularly humid, the resulting tea might have an indolent (or ‘wet’ and ‘dank’) tinge to its aroma and flavour which some people find off-putting, but others consider desirable.



On the other end of the spectrum, a raw pu-erh that is stored in temperate or cool environments might look and taste remarkably similar to when it was first made, even after 10 years or more or storage. Some people may have a preference for this more conservative approach to storing and subsequently transforming their pu-erh tea, arguing that it preserves more of the original character of the tea.


Most people - meaning the market at large - tend to prefer an approach somewhere in-between.

In our experience, the most sought after aged pu-erh teas are ones that have been stored warm and wet enough, and for long enough that there is noticeable changes in the colour, flavour, and fragrance. The purpose of this kind of storage is to preserve and enhance some of the tea’s initial characteristics but without any detectable elements from the storage itself (i.e no ‘wetness’ or ‘dankness’).

To sum it all up, there’s a method to the madness of pu-erh storage. The more balanced the method, the more desirable the proverbial madness.

Effective storage of pu-erh tea

Depending on your desired outcome, effective storage of pu-erh tea can involve many different approaches. In our eyes, effective storage means encouraging microbial activity within the tea cake through careful control of environmental conditions.

In this section, we delve deeper into the role of microbial activity: what it achieves and the key factors that influence its progression.

 

The role of microbial ripening


Aging pu-erh tea is a process of microbial ripening.

Microbial ripening is a multilayered process in which bacteria, fungus, and yeasts — from both the environment and already on and in the tea itself — slowly transform the tea. Over the course of decades, the diversity and populations of these microbes fluctuate as their food sources change. One bacteria eats something and produces something else, which is perfect food for a certain type of fungus, and so on and on the chain of events goes.

These microbes have something in common — heat makes them work faster. Some of the major centres for pu-erh tea storage in the last half a century have been Guangzhou, Hong Kong, and Taiwan; all places with consistently hot and humid climates. Interestingly, Kunming, in northern Yunnan, is also a city where vast amounts of pu-erh tea are stored, although it has much cooler climate.

At the most basic level, tea that is stored in hot conditions ages more quickly than teas stored in cool ones. Humidity plays a role too, but a secondary one to temperature. While microbes need enough moisture to survive and reproduce, ambient humidity is only part of the picture as the most important factor determining their survival is the moisture content of the tea leaves themselves — and what determines stable moisture content in the leaves? The temperature of the surrounding environment.

Let’s break it down a bit.

Key factors behind microbial ripening

Tea is very hygroscopic, it absorbs and loses water from the air very easily and quickly. For example, dried tea leaves can range from approximately 3-18% moisture by weight.

Think of a tea cake like a sponge; if the air is humid enough (i.e around 60-70% or above, depending on the temperature) it will continue to absorb water until it is fully saturated and can’t hold any more. When this happens, the risk of mould developing on the leaves rises dramatically.

Similarly, if the air is dry (i.e at and below 45-50% humidity) the tea will leech water into the air until either the ambient humidity stabilises and reaches equilibrium, or the tea leaves have no more water to lose. In total, it’s possible for a pu-erh tea cake to lose about 97% of its overall moisture in extremely dry conditions. The remaining 3% is water that’s locked inside of cells within the leaves — to dry this out too, you’d need to heat the leaves to approximately 100C (or 212F). 


When a tea dries out completely, it can lose its flavour and fragrance through volatilisation of the essential oils and other compounds. Once these compounds are no longer bound strongly enough by water, they essentially evaporate into the air.

To continue the sponge analogy, picture a huge warehouse room with nothing in it but a single tea cake. A tropical storm rolls in and the humidity in the room starts to climb to nearly 100%. That poor little tea cake absorbs as much humidity as it can but there’s only so much it can hold before it’s fully saturated, at which point it goes mouldy.

Now picture the same warehouse room, but filled floor to ceiling with hundreds of boxes of tea. The capacity of the sponge is much larger, and even a few days of elevated humidity is easily absorbed into the mass of tea. Once the storm has passed and the humidity begins to drop again, the tea will leach out some of the extra water it absorbed no problem, until a new equilibrium is reached.



This is the mechanism at play in warnings we’ve heard from people in places like Guangzhou, telling us that tea in storage will be just fine — but bring a single cake out of its highly absorbent warehouse environment and leave it on your kitchen counter and it will go mouldy. By understanding these basic principles of humidity, temperature, and equilibrium with the environment, we can approach storing tea at a smaller scale (such as at home) with a few good principles to take the pedantic guesswork out of it.

 

 The challenge is to not drink through everything; easier said than done.

How to store pu-erh tea at home

Now that we’ve unpacked the basic principles behind effective storage, we can move on to sharing our tips for storing pu-erh tea at home.

A good storage has the following characteristics:

1. It’s free from pests, sunlight, and strong smells.

Because it’s highly hygroscopic, tea is incredible at absorbing fragrance from an environment. For this reason you want to keep the tea in some kind of resealable food-grade (unscented!) bag and away from any strong scents including household cleaning chemicals, incense/scent sticks/oil burners, herbs and spices, cigarette/vape smoke, perfumes and fragranced cosmetics, mothballs, and so on.



If you want to be extra careful, we recommend considering the tea’s positioning and placement within the room itself. For instance, storing the tea inside a cupboard off the floor might offer good protection from sunlight and any risk of rising damp — but if that cupboard houses strongly aromatic herbs and spices, you may need to try another spot.

2. It has stable climatic conditions. 


This means avoiding an environment that undergoes any extreme swings in temperature or humidity. 
To put things in even more basic terms, don’t set up your storage near a heater or air conditioner, near any sources of open flames (i.e. 9 times out of 10, the kitchen is no-go), close to a window, or in humid room (i.e. not the bathroom, laundry room, kitchen, or garden shed). 

Common sense goes a long way, but if you’re hardcore stickler for details, a control freak, or on the road for large portions of the year (like us), we recommend investing in a basic digital temperature humidity monitor (aka a thermometer and hygrometer) for piece of mind and peace in your heart. 

3. It is easy to access and monitor, and serves your end goals.

Somewhat self explanatory, but ideally you want to strike a balance between longterm entombment and moderately-easy access to the stored tea. While you might not plan on drinking it any time soon, easy access to the tea means it’s easier to catch and correct any issues before they spiral out of control. 

This might seem pedantic, but trust us; some rooms seem stable until the dead of winter/peak of summer and it’s better to catch these things early than to find the tea in a bad or undrinkable condition due to years and years of unmitigated exposure to various unfavourable elements in the storage environment. 

Conclusion

And that’s it for how and why to age pu-erh tea through intentional storage. This isn’t the only way to store pu-erh but it’s how we like to do it.

If you have any further questions on the topic or interesting experiments to share with us, we’re all ears. Send us a message on Instagram @kuuracorp or fill out our Contact Form.