Workers check the fermentation of dark tea in a tea factory. (PHOTO: XINHUA)

By ZONG Shihan

Dark tea is named for its dark brown color, which results from the use of coarse aged tea leaves and the long period of pile-fermentation during processing. Different from the oxidation of oolong tea and black tea, the post-fermentation of dark tea is a unique process of piling with microbial participation.

The production process of dark tea involves fixation, rolling, piling and drying. Among them, piling is a unique feature of dark tea. It requires stacking tea leaves and adding water appropriately to encourage the rapid growth and multiplication of microorganisms on the tea leaves at a specific temperature. This process can last from a few hours to several months, endowing dark tea with its unique non-bitter, non-astringent taste and mellow flavor.

The long production process and the waiting time for piling of dark tea demonstrate respect for time. Unlike other teas, the quality of dark tea is not valued for its freshness but for its aging, as it becomes more fragrant over time.

In history, dark tea was a great companion for people living in China's border areas to drink and counteract the greasiness from food. It traveled from inland areas, along the Ancient Tea Horse Road, traversing thousands of miles, to reach China's northwest and southeast border areas. Later, dark tea was exported to Central Asia, Russia and Europe, creating a glorious history of the Sino-Russian Tea Road, also known as the 10 Thousand Li (5,000 kilometers) of Tea Road.