Black tea is fully fermented tea. The tea leaves undergo an extended period of indoor withering, then are rolled to severely damage the cell membranes of vacuole of the leaves. This causes the tea polyphenols and oxidizing enzymes to have a reaction. Finally, there is supplementary fermentation to turn the underside of the leaves completely red. Taiwan black tea is mainly manufactured out of tea from large-leaf cultivars, such as TTES No.18 (Ruby). The appearance color is a glossy black tinted with purple. The liquid color of the steeped tea is reddish-gold, and there is a slight cinnamon aroma and mint fragrance to it, while the flavor is sweet and refreshing. TTES No.21 (Honyun), which came out later, has the fragrance of citrus flowering plants. Together, the two cultivars are creating a new image for highly aromatic black tea from Taiwan. In recent years other tea-growing areas have been using fresh tea leaves of small-leaf cultivars as raw material to manufacture small-leaf type black tea, or using tender tea buds that have been pierced and sucked by the small green leafhopper to make honey-flavored black tea, and both of these types are popular with many consumers.

　　Black tea is best when it is jet-black in color, glossy, and is tinted purple. The strips of tea are tight and uniform, with those having golden-yellow white tips being the best (except for TTES No.18). The liquid color of the steeped tea should be bright red, clear, and with a glossy tint. Black teas manufactured using different cultivars each have their own special fragrance, but all are best when pure and rich and the taste is smooth while also being strong and refreshing. The tea is ideal when the underside of the leaves is plump and fresh and the color of infused tea leaves is of a very even red (without green or other colors present) and has a sense of brightness.