Wednesday, October 15, 2008

Perspectives on Storing and Aging Pu'er Teas (v): Concepts and Methods of Storage


[[EDITOR'S NOTE: The series continues with this, Niisonge's third instalment. Parts i, ii, iii, and iv of the series can be read here, here, here, and here.]]

What do you store your pu'er in?

In storing sheng pu'er, people want to be clear in what ways storage is possible. Here we will discuss a few methods that some pu'er lovers use to age pu'er. But first, you need to understand some storage concepts:

1. Aging

Aging -- what exactly is it? Aging pu'er has the goal of developing the scent and flavor characteristics in both dry and brewed infusion; and to stabilize and complete the quality of pu'er tea. The factors that affect the aging process are: temperature, humidity, oxygen, light, extraneous scents, moisture content, time.

2. Dry Storage Vs. Wet Storage

There are two approaches to aging pu'er: “dry storage” and “wet storage.”

Dry storage means to store pu'er in relatively dry conditions and allow the aging process to naturally take place. But too dry of an environment will slow down the aging process. So a certain amount of humidity is required. Dry storage requires decades for the tea to age satisfactorily. Pu'er that is dry stored will have a mild taste. It is the preferred method for storing tea.

Wet storage means to store pu'er in a relatively humid environment, and can speed up the aging process dramatically. Since humidity can be controlled, you can get varying speeds of aging. Indeed, wet storage can be divided into 3 main forms: heavy humidity storage, medium humidity storage, light humidity storage, which then begets the following: heavy humidity aged pu'er, medium humidity aged pu'er, and light humidity aged pu'er. However, too high a humidity in storage will lead to speedy mold formation, which is not good for pu'er. Wet stored pu'er will have a stronger flavor than dry stored pu'er. And it will have a characteristic earthy, moldy flavor.

Because wet storage can cause mold formation relatively quickly, it is not considered a suitable way to store pu'er. And the molds that form on the pu'er may contain elements like mycotoxins that are harmful to the body.

3. Segregation or Quarantine in Storage

In storage, you should segregate or “quarantine” bings. That is, sheng should be stored with sheng, shu should be stored with shu; and partially aged pu'er should be stored with partially aged pu'er. Because they are all at various stages of microbial development; so you don’t want your sheng bing’s microbe colonies to be overpowered by those of a shu or aged bing. And more importantly, you don’t want a moldy bing to spread and infect other bings in your collection (think microscopic spores here).

4. Storage Environment

The storage environment should have ideal conditions such as away from sunlight, rain, and clean. It must also be airy; there should be air circulation -- because the microbes in pu'er are oxygen-loving critters. And it must be free from extraneous odors. So no kitchen smells, perfume smells, etc. And be careful of what you store pu'er in -- cardboard gives off odors, so does particleboard, stained/varnished wood, and even some woods like pine emit odors. So unless you want a piney scent in your pu'er, better to keep it away from odor sources; which will absorb into the tea, and impact the delicate flavor.

5. Mold Growth

Mold is the enemy. About every 3 months or so, you need to thoroughly check your pu'er collection for signs of mold growth. Mold is not good. Once bings go moldy, the mold will spoil the flavor of the tea. Instead of becoming aged tea, it will just be moldy tea. This is where moisture content of pu'er is important. When the humidity is too high, the tea will suck up more moisture -- leading to mold growth. So mold can be kept in check by controlling humidity, and therefore moisture content in pu'er. Ideally, pu'er should be about 10% moisture content.

But you do have to acknowledge though, that microbes like Aspergillus niger, Penicillium chrysogenum, Aspergillus clavatus, Rhizopus chinensis, and others are all molds that are naturally present during the aging of a sheng pu'er. But, in minute quantities they have a beneficial effect. If under humid conditions, they are allowed to explode in growth -- then, that would just change the tea for the worse -- into a moldy mess. So it’s best to avoid mold on the surface of your tea. You might want to air out moldy bings on a shelf to reduce the moisture content.

6. Time

Time is important. A sheng pu'er needs at least 10-15 years to age well, before you get a good result with the tea. And so there is the common saying, “the more aged the more fragrant” pu'er becomes. And this is especially true when sheng pu'er is stored properly to age.

7. Post-aging Storage

Post-aging and pre-drinking storage is important, but we will get into that later.

Pu'er Storage Methods

1. Original Packaging 包裝紙

By far the best way to store pu'er is in its original packaging. Bing chas should be kept in their individual paper wrappers. If you have a tong of bings, it should be kept intact as a tong. Let bings of the same ilk be together. But don’t mix shengs with half-aged pu'er, or with shu bings.

2. Dedicated Pu'er Storage Room 專門貯藏室

Ideally, there you should have an entire room dedicated to storing pu'er, that is temperature- and humidity-controlled and has good air circulation. Ideally, the temperature should be about 25 degrees C. and at 75% humidity maximum. Again, with shengs stored separately from shu and aged. And a dedicated storage room should be free from filth, pollutants, extraneous odors, and light. Of course, you know that already, don’t you?

3. Wooden Shelf 木架

For bing cha, tuo cha, and any other kind of large pu'er, they should be stored to age on untreated wooden shelves, to facilitate air flow. The wooden shelves themselves should be of a scentless wood, to avoid tainting the pu'er with an extraneous scent.

Every three months, you should turn them over, and examine whether there is any mold development, insects, etc. If you find mold, then you need to move your collection out, and determine the extent of the mold, and clean any bings of mold infection. Excess mold will cause undesirable qualities to develop in the pu'er, which will cause the aroma and flavor of the tea to change -- for the worse. If you do find mold, and lots of it, that means you probably have a humidity and/or ventilation problem. See what you can do to remedy the problem.

4. Large Earthenware Jars 陶缸

These are very large jars, with a wide mouth, meant for storing a lot of pu'er cakes. They provide a dark enclosed environment for aging sheng pu'er, allowing the pu'er to “incubate” together, and age together. Although the earthenware is porous, it’s not as airy as a wooden shelf. Storage in such a closed environment, like these large earthenware jars means the scent of pu'er will develop together -- and not be tainted by extraneous odors -- like say, sitting on a shelf in a room where smoke happens to waft by. But you wouldn’t be smoking or burning incense around your pu'er, now would you?

Some pu'er people in Taiwan actually like to “improve” the scent and flavor of their bings by adding camphor wood in between the bings. The camphor aroma will then be absorbed by the pu'er, and be present in the tea. But is that really a good idea? There is some logic to it though. In the wilds of Yunnan, pu'er trees grow alongside cinnamon trees. And the scent of cinnamon is absorbed by the pu'er -- which is a desirable quality. Maybe putting cinnamon bark into an earthenware jar with some bings to age for a time could improve the flavor? I don’t want to try.

5. Cloth Bags 棉普洱袋

There are simple, round, heavy muslin cotton bags in China that are used especially for storing pu'er bings. These are actually useful, because paper wrappers get torn, but the cloth bag is breathable, yet keeps out dust. They can be large enough to store a tong of bings. So that’s also a storage option to be considered.

6. Earthenware Jars 陶罐

Small earthenware jars are good for storing loose pu'er. And once your pu'er has aged for a desirable amount of time, you can then break up a cake, (or -- for tuo cha -- steam it, break it apart, and dry it reasonably), and put it into porous earthenware jars. Cover the jar with paper or cotton cloth for a time, not the lid.

The Other Side

There are some people who say that mold is natural for pu'er. They claim it’s a natural part of the aging process. And they even tolerate the generations of mold growth on their bings -- white mold and yellow mold, green mold or black mold. But is that really a good idea? Why risk mold and possibly tainting the tea, and worse, ruin years’ worth of effort to store tea? A small amount of mold is tolerable, even expected. But when found, it should be dealt with quickly. And the mold should be cleared away. A very moldy bing will likely end up tasting moldy; and at the very least, vigorous cleaning will have to be done to take care of the mold problem. By far, it’s much better to avoid mold, if at all possible. Just because a bing has turned moldy doesn’t mean it has aged. Mold growth can happen fairly quickly (as I have demonstrated already) -- especially in a hot and humid environment. Aging pu'er takes years. And besides, who wants to run the risk of consuming mycotoxins?

Then there are those who say that the aging process for shengs can be sped up by storing them in a large earthenware jar with some aged pu'er. They advise you to remove the wrappers, and let the microbes “mix.” The microbes in the aged pu'er will migrate to the new pu'er, and this supposedly will “quicken” the aging process. Also, the aged scent of old pu'er is supposed to be sucked into the new pu'er. But could this method really work? First, you should know that microbes in pu'er -- some start out during the manufacturing process -- but quickly recede after processing and then after the first year. And during successive years various microbes live and die, with mainly Aspergillus niger remaining. So adding Aspergillus niger from an aged bing to a new bing isn’t really going to have any effect -- because Aspergillus niger is already naturally present during the aging process. You’re not doing anything that nature won’t do itself. So why bother? You might however, end up adding lots of unwanted, invisible mold spores to your new bings which might get moldy if neglected for a long time. Here, let me spore you some tea!

Just remember, when looking at storing pu'er, you need to think about the long term if your pu'er is to age and mellow. Time is an important element in storing pu'er, maybe just as important as what you choose to store your pu'er in.

Post-aging Storage

Ok, 30 years or so have passed, and your shengs have now become aged pu'er. You take one out, break it up with a pu'er knife, and then ... yeah, you still should store it for a while longer. Use a small earthenware jar. Put the broken pieces into the jar. Cover with cotton cloth -- not the lid of the jar. You want air to circulate in the jar. Why should you not drink it right away? Think of the pu'er in layers. There is the surface layer, and the inner layer. For all these years, the surface layer was exposed to everything -- all the air, etc. And the inner layer wasn’t so exposed. The surface layer will be a bit mellower, while the inner layer will have a stronger scent and flavor. So you want to mix these 2 layers up in an earthenware jar and sit for (say) two weeks, just so that everything balances out, and reaches equilibrium. Then, you can better enjoy the tea. And the teas flavor and scent will be better balanced out. We call this the “Tea Qi Blending Method” (茶氣調和法).


darwin said...

this is really a very relevant read for me as there are lots of things concerning high humidity level storage here, thanks very much warren!

i do want to clarify some things about (here i go again...) clay jar storage....

as i read about puerh, its clear that they really need to breathe, be it sheng or shou, they need mild exchange of air, but not too much, and the only time it needs "more air" is when its really humid, that set straight, if i use clay jars, then its an ideal situation, dark, breathable spaces, perhaps opening the lid once a week or once every other week to circulate fresh air into the tea cakes. during summer or sunny days, there should not be any problems. but what about during rainy and very humid days? would it be correct to just close the lid until the sun comes out again and its not humid anymore? the logic behind it is to not let the humidity enter the jars...
and what if there would be molds? what shall i do? just the usual brush and sun dry in a cloth bag? then back to the jar again?

thanks very much for your inputs!

Warren said...


The clay storage jar is by far the best thing to use to store puer, even better than a box.

Boxes tend to leak air, so it doesn't seal in the scent of the tea as well as the earthen ware jar. And the boxes emit a peculiar smell. But a lot of pu'er collectors still like to use cardboard boxes - mostly because they're cheap and plentiful.

With the earthenware jar, make sure the inside is very clean, and fully dry. Then, put in some dry wood charcoal chunks at the bottom. Don't be cheap with the charcoal. Use lots of it. It's fairly cheap anyway. You might want to put the charcoal into small cotton sacks. To save you from having a black mess at the bottom and on your puer. (You could probably use some thin rice paper instead too.) Then, put in your pu'er and cover the jar. Any moisture that gets into the jar will then be sucked into the charcoal. So that can really help to save your tea from getting moldy.

But in general, putting the tea cakes into the earthenware jar without any charcoal should be good enough. It should't get moldy like that.

Once in awhile though, it's good to take the cover off the jar, and just cover it with cotton cloth, and let new air into the jar.

And that should prevent any mold problems while at the same time allow you to store your puer securely and safely.

And if you still have any mold problems, then, take the moldy ones and sell them on Ebay. Hahahaha.

But if you see mold, just let them air out and dry a bit, and then scrape/brush off the mold with a brush.

If you see aged pu'er cakes, and you see the edges are really ragged - that's because they have been brushed vigorously to remove all traces of mold.

darwin said...

thank you very much warren for your inputs,

after reading your reply, and to do your input justice, then i really have to phone the jar factory up in northern philippines to book my jars. there's no shortage of wood charcoal here as they are readily available and really cheap to buy.

over the past 2 weeks,ive experimented with cardboard box storage. this was what happened... on a sunny day, i placed some of my ripe pu erh and some charcoal in a box, then after a few days, it began to rain for about 3-4 days, not all day rain but "on-off" rain, but not much sun during intervals. and after being in the box for a week and a half, just last sunday, when i opened the box, i was shocked to see mold on cakes for the first time! so i scraped them off, and sun dried the cakes for a few hours. for a second i thought that the culprit would be the charcoal, but i think it was because the cakes were still a bit damp inside and i did not really dry it out completely before putting it in the box...

what i'll be trying out it would be to bring those damp cakes to the office, and just leave it there for a few weeks, and after they have completely dried out, then ill bring them back home, and hopefully, my jars would have arrived by that time...

thanks very much for your inputs warren, they are invaluable,
if i get the chance to go back to china within the year, and go to quanzhou fujian, maybe i can go on a short day trip to fuzhou and take a look at the tea market there. =)

Antonio said...

Very interesting article, full of useful information. thank you!

I have a quick question: would you suggest storing young sheng (I mean from 0 to approx. 10 years of age) in an earthenware jar?

I have been storing my aged sheng (from the '70s and '80s) in earthware for years now (I live in Northern Italy, where humidity can be high, both in summer and winter), with excellent results, in my opinion. No mold and great taste. And sniffing the magic smell when taking the lid of the jar is always inebriating...

But I bought this puerh already "aged".

What about storage of young stuff? My concern is that if I put a 2008 bing in a jar, it may double the aging time (say 30 years of aging before getting some signs of mellowness).

Any suggestions? Maybe just leave these new babies on a clean shelf?

Many thanks!

Warren said...


Yeah, go ahead and store those young shengs in their own earthenware jar.
They will mellow and age, and the earthenware jar will keep in all the tea scent, while at the same time being breathable.

But here's the thing: no one has done a definitive study on how exactly to use earthenware jars to store puer. Some people say that moving the jar around from location to location in the house makes a difference. They say that it's best to store them in a cool, dark and airy location.

Think of the earthenware storage jar as a miniature store room for pu'er tea. And inside that jar should be the ideal conditions to post-ferment and age pu'er tea.

So it shouldn't hurt to store young shengs in the jars.

darwin said...

hi warren,
would you be having another installment of pu erh storage?
we want more =)


Warren said...


Yeah, I suppose I could write another article. It will take some time though.

darwin said...

hi antonio,
mind sharing some pictures of your earthware jar? what type of clay was used and is it glazed or unglazed jar?


Robert said...

Great information there. As a puer fan for over 14 years, I've acquired quite a bit tea collection. I live in Taiwan where there is good humidity and temperature for puer storage. I keep it in a store room where there is little in the way of "off" odors.

In my experience, puer seems to change very little the first 5 years or so then accelerates more after about 10 years.

I'm glad I bought some of the older teas long ago though since the price has sky rocketed since.