There are two different ways a pu-erh tea can be classified: raw (sheng) and cooked/ripe (shou). This is due to the amount of processing that occurs after the tea leaves are picked and withered.
With raw processing, the leaves are withered then heaped into piles, much like a compost pile, allowing bacteria to ferment. This is the most important step of the process, called “Wo Dui” (moist track). This is the point where the character of the tea begins to develop. The leaves are then partially pan fired in order to halt enzyme activity, lightly rolled and kneaded, then left to dry in a “Dry Storage” environment with enough moisture to allow the tea to slowly oxidize over time. At this point, the tea is immediately compressed into cakes or left in loose leaf form.
The cooked processing method was developed in the early 1970’s by the Yunnan Kunming tea factory to speed up the process of production. With cooked processing, the tea leaves are picked and withered then mixed with a bacterial culture created to replicate the bacteria that would be created during natural fermentation. Then, the pu-erh is left to fully oxidize for up to 40 days in a hot and humid environment before firing, creating a dark, earthy infusion.