In traditional processing, optimum fermentation is reached after two to four hours. Fermentation is stopped by heating or firing. This firing also preserves the leaves. Traditional firing was done on large pans or screens over fire, but now a drier that blows heated air into a chamber is used. In the drier, the leaves are cooled quickly to prevent overdrying and loss of quality.
Black tea is the most popular type in the United States.
Black teas are processed the longest and have a rich, reddish brown color and full aroma and flavor. Some well known types of black tea are Orange Pekoe, Darjeeling, and English Breakfast. Green tea is unfermented tea. The leaves are steamed immediately after harvest to prevent fermentation and maintain pliability. The leaves are then rolled and fired until they turn dark green.