Black Tea Leaves
Black Tea is created naturally (no catalysts or additives) by allowing the rolled leaf to set out, exposed to air, for a period of anywhere from 1 to 12 hours depending on the grade.
The process by which the leaf turns brown is called oxidization and is very similar to the way an apple turns brown after peeling. The rolling process breaks up the cell walls of the leaf so the leaf will then turn brown when mellowed or allowed to set.
After the desired amount of oxidization occurs, the leaf is then fired to suspend its flavor profile and preserve the tea.