The western world knows this sort of tea as Black Tea, however in China it is known as Red Tea because of the tawny colour of the leaves once brewed. This is an oxidised tea. Once picked, the tea is withered for a few hours. This can be done in the sun, or in rooms with circulating air. During this process the leaves lose a large amount of their moisture, a little over 50% and they become a brown/red colour. Leaves are then rolled, this is usually done by machine on either wood or copper. Rolling usually takes around 20 minutes. Once rolled leaves are laid out flat and left to oxidise. This process can last a varying amount of hours and of course has a large effect on the flavour of the finished tea. As an example Darjeeling usually ferments for around an hour. Leaves are then fired to stop fermentation and remove excess moisture, turning them the finished brownish colour.