Withering reduces the moisture content and makes the tea leaf pliable which prevents it from breaking during ‘rolling’. It also activates certain elements in the leaf essential for produce quality tea. Leaves are spread out on withering troughs and a flow of cool air helps the process. Withering could happen indoors or out of doors depending on the region and tradition of tea manufacture.
Rolling brings out the flavor of the tea by bruising the leaves and starts the process of oxidation. An art perfected over centuries, rolling of Oolong tea is done in much smaller machines compared to those used in black tea manufacture. Again, the method of rolling will depend on where the tea is made.
Hot air is passed over the fermenting tea leaves to deactivate fermenting enzymes. This process is critical as otherwise the tea leaves will fast deteriorate affecting its quality. It also further reduces the moisture levels.