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While there are limits to the humidity levels that can be chosen, in the end, it comes down to personal preference depending on which taste you want your tea to develop in the future.
Anyone who further and further expands their Pu Erh tea collection will sooner or later wonder about the optimal storing conditions.
SHORT ANSWER – What Is The Right Humidity For Pu Erh Tea Storage?
The humidity has a heavy influence on the aging process of Pu Erh tea. Humidity levels between 50% and 70% are considered ideal for long term storage. Too high humidity causes mold. Too low humidity stops the aging process.
This allows for the tea to properly develop an aged taste, while not growing mold or bacteria. Depending on the desired outcome of dry or wet storage Pu Erh tea, you would need to adjust the humidity in your storage containers.
Below I have collected information on the influence of humidity on the development and aging of Pu Erh tea. If you want to know how to achieve a dry or wet stored Pu Erh tea and at what humidity levels you risk destroying your collection, feel free to keep reading.
What Influence Does Humidity Have On Pu Erh Tea Storage?
When Pu Erh tea is stored for a long time, be it a month or years, the taste will change. The development of Pu Erh tea is influenced by more than one process. Active enzymes, microbial life, fungi and decomposition work hand in hand and change the chemical composition of your tea.
Depending on the temperature at which the Pu Erh tea is stored, some processes are faster and some might completely stop. The same goes for the humidity levels in the storage container.
Decomposition reactions, especially through UV light, do not need humidity to work. Enzymes can work with low water content in the tea, too. Microbial life and fungi will need higher humidity to have a noticeable influence on the tea.
Storing Your Pu Erh Tea Too Wet
With too high humidity levels above 70% to 75%, you will encourage the growth of unwanted species on your Pu Erh tea collection. Especially mold will quickly cover your tea if liquid water condensates on either the tea or the storage container.
Even if no mold grows at high humidity levels, there still is a risk for growth of microbial life and bacteria that will not be as obvious to the eye.
When preparing and tasting the tea you might notice a sour and acidic taste. This is the result of bacteria, which produce acid while digesting the tea.
Storing Your Pu Erh Tea Too Dry
When Pu Erh tea is stored at very low humidity levels, the tea will not properly age. Both microbial life and fungi are required to develop the aged taste we all love. These need humidity to reproduce and do their work.
You do not want your tea to be overgrown by mold or acquire a sour taste from bacteria, but you should not dry your tea below 45% to 50% of relative humidity.
If you fall below these levels the only changes to your tea would be through decomposition, oxidation and to a lower extent through enzymatic activity. This will result in very very slow aging or even halt the positive aging effects.
How Pu Erh Tea Is Aged In China
You may have read dry and wet storage when purchasing aged Pu Erh tea from different vendors. These terms are not clearly defined and are often used in combination with larger cities in China like Hongkong or Kunming.
Since China has a very large land area and different climates, people have developed different preferences for storage humidity. Normally Hongkong is known for wet stored Pu Erh tea, but prominent examples stored in Hongkong have also been dry stored.
It is not easily possible to derive the storage humidity from the storage location. The best and most straight forward method to determine this would be to taste the Pu Erh tea and taste the difference.
The difference between wet and dry storage will be covered later. Another option is to look at the color of the resulting Pu Erh tea cakes since wet stored Pu Erh tea has darker leaves than equally old dry stored Pu Erh tea.
Any Pu Erh tea storage with humidity levels between 65% and 75% can be considered wet storage. Over years or decades, the tea will develop a characteristic wet storage taste that some people love and others find disgusting.
The wet storage taste often includes notes like wet hay, wood, forest floor, animal barn (not necessarily in a negative way!) and mushrooms. These darker notes are the result of the metabolism of different microbial lifeforms and fungi.
If you have never tasted wet stored Pu Erh tea, I would recommend you to try a four or five year old cooked (Shou) Pu Erh tea. Some of the notes found in wet stored aged Pu Erh are very dominant in this type of Pu Erh tea. This is not the same, but you might get a better idea.
Since these fungi are not always safe to consume, you should always rinse wet stored Pu Erh tea with boiling water. If you want to be safe a second rinse can be a good idea.
If you do not want your Pu Erh teas to develop intense dark and damp notes, you can choose humidity levels between 50% and 65% for you Pu Erh tea storage. This will ensure that neither bacteria nor fungi will reproduce too much and possibly spoil your tea.
The dominant aging processes in dry storage are enzymatic activity and natural decomposition. This will result in the slower decomposition of bitter compounds found in young Pu Erh teas. A dry stored Pu Erh tea will take longer to reach an easy-to-drink age and also be more expensive nowadays.
Pu Erh tea that has been stored in low-medium humidity environments will still have some fruity and floral notes remaining and can sometimes appear much younger than it is.
Changes In Humidity Levels
As everyday food items are not supposed to be stored under variable temperature or humidity, such conditions have a major impact on Pu Erh tea storage, too.
The changing humidity can result in condensation. As described earlier, condensation may cause your Pu Erh tea to become moldy and undrinkable.
Another effect of changing humidity levels is more rapid aging with more wet notes. Microbial life and fungi are the dominant taste developing factor when stored under changing humidity, same as wet storage.
Why Temperature Matters
Relative humidity is correlated to the temperature of the surrounding air. If you drop the temperature quickly, you will notice the condensation of water on your tea and storage container.
This might spoil your tea! On the other hand, a rising temperature will result in a lower relative humidity and therefore result in a slower aging process.
Depending on your personal preference for taste, you can control the taste development of your Pu Erh tea. If you want floral and fruity notes to be dominant, dry storage with humidity levels of 50% to 65% would be ideal.
If you want wet and dark notes to develop you should aim for 65% to a maximum of 75% relative humidity. Just be careful not to grow mold on your tea or otherwise damage your collection.
There’s a lot more to learn about tea! If you are looking for a good place to start, I highly recommend the book Tea: History, Terroirs, Varieties. You can check its current price on Amazon here.