Black Tea accounts for the largest production volumes and is produced everywhere except, possibly, Japan. Processing begins with withering (air drying) to remove about 30% of the moisture. The leaves are then rolled under pressure to release sap, which starts fermentation. The intensity of the rolling process determines whether the finish product will be whole leaf, broken, or a mixture of both. CTC (crush, tear, curl) is a mechanical form of rolling designed to produce a small, uniformly sized cut tea used most often in teabags, but also sold loose. After rolling, fermentation is allowed to continue and is usually complete within 3 hours. Fermentation turns the leaves a copper-brown color. The tea is then dried with hot air to stop the oxidation process and dry the leaves as well as the sap that was released by rolling. Depending on how much sap was released in rolling, the final color will vary from coppery-brown to black. Finally, the tea is screened to separate the various leaf grades of full leaf, broken, fannings, and dust. Note that leaf grades only refer to leaf size. They do not indicate the quality of the tea.