Aging

Aging is the step that happens after the tea has left the factory and for some teas it is the most important one. A raw puerh cake is not finished when it is pressed; it is finished twenty or thirty years later, by air, humidity and time. It is also the only operation on this list that the drinker performs, which is why storage is the subject puerh people argue about most.

What it is

Deliberate slow change in storage. For puerh the conditions are specific: roughly 20-30°C, steady humidity between 60 and 70 percent, a dark room with air moving through it and nothing aromatic nearby, because tea takes on the smell of whatever it is kept with. Below 20°C the change slows a great deal. Raw and ripe cakes are stored apart. Hong Kong developed a faster version, wet storage, holding the tea at around 30-35°C and up to 90 percent relative humidity, which accelerates the change sharply and tastes of having done so.

What it does to the leaf

Both mechanisms run at once and which one leads depends on how warm and how damp the storage is. Slow oxidation continues wherever the leaf meets air and microbial activity continues alongside it, which is the natural post-fermentation that keeps a cake moving for decades. The astringency of a young raw cake fades, the bitterness softens and the liquor darkens, over years rather than weeks. Sheng is not considered fully mature until it has been aged for around thirty years, at which point the trade calls it vintage.

How it's done

Mostly patience, in three shapes. Natural storage is the default: correct temperature and humidity, dark, ventilated and left alone for years. Wet storage speeds it up with heat and moisture and is a deliberate style rather than an accident. Two teas use aging as a working step rather than a resting one. Aged oolong is re-fired every year or every two to three years, so the roast and the age accumulate together. Anhua's Fu Zhuan brick goes further: it is held warm and damp after pressing until a golden fungus, Eurotium cristatum, flowers through the cake, which is a controlled operation of weeks rather than a wait of years.

What it tastes like

In raw puerh, a long trade of sharpness for depth. Young sheng is bitter, astringent and bright, and decades take it somewhere quieter and rounder. Ripe puerh changes much less, because the pile already did most of what age would have done and it is generally agreed to improve only slightly with keeping. Aged oolong goes mineral: after twenty to twenty-five years those notes appear clearly enough that the comparison the trade reaches for is aged puerh.

What people get wrong

Treating age as a quality claim. Aging is a process a tea undergoes rather than a grade it earns and a mediocre cake aged for twenty years is a twenty-year-old mediocre cake. The second mistake is assuming any tea improves with keeping. Ripe puerh gains a little, green tea loses steadily and the teas built to age are built for it: pressed, sun-dried and coarse enough to survive the wait. Storage is also not a passive act. Temperature, humidity and airflow are decisions and a cake kept next to coffee will taste of that decision.

Styles where this step is distinctive

and 8 more

teabert, the tealytics teapot, keeper of the kettle

Whatever you are keeping is also absorbing the room. Store it dark, ventilated and nowhere near coffee or spice.

Sources

puerh should be aged between 20 and 30°C at a constant 60-70 percent humidity, in a dark, well-ventilated room away from aromatic substances, with sheng and shou kept separate; below 20°C the process takes much longer Gascoyne et al., Tea: History, Terroirs, Varieties (2014), 'The Processing of Chinese Teas'
Hong Kong wet storage accelerates aging by holding the tea at around 30-35°C and 90 percent relative humidity Gascoyne et al., Tea: History, Terroirs, Varieties (2014), 'The Processing of Chinese Teas'
sheng puerh is aged for 10 to 50 years and is not considered fully mature until around 30, when it is called vintage; shou is meant for immediate drinking and its flavour improves only slightly with age Gascoyne et al., Tea: History, Terroirs, Varieties (2014), 'The Processing of Chinese Teas'
aged wulong is re-fired annually or every two to three years, and after 20 to 25 years develops mineral notes that resemble those of aged puerh Gascoyne et al., Tea: History, Terroirs, Varieties (2014), 'Processing Green Wulong Teas'
storage is regarded as an extended and essential part of puerh production, and in that natural post-fermentation both oxidation and microbial reaction may occur depending on the temperature and humidity Zhang, Puer Tea: Ancient Caravans and Urban Chic (2014), appendix 1