For most kind of teas it is the process after the harvest that will determine the quality of teas.

After the harvest the leaves a fermentation will start (oxidize) if let in a damp state, during which it will sustain physical damage and change color. For white teas there is no fermentation, green teas are made from leaved that fermented for less than 20%, oolong teas are allowed to ferment between 20~50%, some kinds for up to 80%, whereas black teas are fully fermented.

Some tea leaves are also rolled in order to accelerate or emphasize the fermentation. This process will also affect the taste, as well as the content of caffeine and the anti-oxidants polyphenols. Some growers of organic tea refuse to roll in order to prevent too many changes.

The fermentation is stopped by drying the leaves, usually in electric ovens or in some cases also above charcoal fires. The moisture content is brought down to 2-3%.