Compression and Storage – Why It Matters

As I’ve previously mentioned, heicha (黑茶 – heicha; literally “black/dark tea”) is any type of fermented or post-fermented tea. The most famous type of heicha is puerh (普洱), made in Yunnan Province. For storage, puerh is pressed into various forms (see my “What is Puerh Tea?” post for more about this).

How do these different forms and compression affect the overall aging of the tea? I’ve mentioned in a few of my reviews about a tea’s compression being tight or not. Compression, more than shape, is a higher contributing factor to the aging process. The shape of puerh tea mainly affects the ability to store it nice and neatly in a pumidor or other storage place.

Heicha ages due to fermentation, which is carried out by types of molds. Now, I’m not a scientist, but if you want to read more on this, this might be a good place to start. Exposure to humidity and oxygen is the catalyst for microbial growth, which fuels the endo- and exo-oxidation of the tea (the aging process). Without the humidity and oxygen, the microbes are dormant and, could possibly, lessen over time.

Why does this matter?

For the average puerh drinker, it might not matter at all, but it gives us a glimpse into why the types of compression affect our teas in the long term. Maocha (毛茶 – maocha; literally “rough tea”) ages much more quickly than compressed puerh due to the increased surface area exposed to oxygen and humidity; however, this increased exposure can actually lessen the flavor and scent of the maocha over time.

Compressed puerh, determinant by the level of compression, ages more slowly because of the decreased exposure to humidity and oxygen. The tighter the compression, the less air flow.

An iron cake will have very little air flow to the center
An iron cake will have very little air flow to the center
A standard puerh cake is not as tight and allows for air flow
A standard puerh cake is not as tight and allows for air flow


There are many more factors to puerh aging (I’ll cover these later), but compression is a huge factor. No matter how ideal your climate is, certain styles of puerh compression will still age poorly. Tightly compressed mushrooms (紧茶 – jincha; literally “tight tea”) or bricks (砖茶 – zhuancha; literally “tea brick”) will age slowly and unevenly. The center of a tightly compressed brick could still be relatively green while the outer parts are much more aged.

Experiment for yourself, but keep in mind that compression is a huge factor in aging your tea.

Unitl the next cup.

3 thoughts on “Compression and Storage – Why It Matters

  1. This is a seriously cool primer on compression. I always thought that compression techniques were developed so that the early Chinese tea roadtrippers could transport higher volumes of tea. The tighter the compression, the less likely it was to spoil over the months-long trip. Looser compression was seen as lower quality. However, since teas have been found to “age” as opposed to “not-spoil” in recent decades, it’s only fitting that science-y folks have reasons for explaining why.

    Cool post.

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