As they absorb oxygen, they turn a bright copper color. This is the process of oxidation that produces black tea. The next stage drying, or firing arrests further oxidation and dries the leaves evenly. They are then spread on trays, which travel through an iron box in a continuous blast of hot dry air for 15 to 25 minutes. Firing turns the leaves black.
Green tea is put into a large steamer and heated immediately after picking.
This softens the leaves for rolling and keeps the juices from oxidizing. Green tea does not go through a fermentation process. The leaves are rolled and dried. They remain green, and as they come from the dryer they are put through sieves that divide them into the various grades. Finally they are packed in chests lined with aluminum foil.