These categories value and encourage oxidation. The whole idea of encouraging oxidation in tea began in the 1400’s and has exploded since then. After pluck, leaves are allowed to sit and soften before being rolled. This rolling process causes the leaves’ veins to burst, releasing sugars, oils, and juices. Then the leaf starts bruising, and getting darker, as it absorbs these juices. Once the tea reaches its desired degree of oxidation, the leaves are roasted to caramelize the sugars and dehydrate the leaves.