Oolong leaves are basket tossed after withering. (Withering is moisture evaporating from the leaf.) There is no steaming as the enzymes need to remain active. Basket tossing bruises the edges & exposes the leaf's enzymes to oxygen initiating oxidation. Oxidation provides the flavor profiles of Oolong, 15% resulting in a light cup through 75% resulting in a dark cup. A wide range between ensures an Oolong to suit all tastes. After partial oxidation the leaf if pan fired to finish.
