Achieving the perfect wither depends heavily on controlling airflow and moisture levels. Proper airflow ensures that the leaves lose moisture evenly, while inadequate airflow can lead to under-withered or over-withered leaves. Moisture control is equally important, as too much moisture can lead to mold growth and poor fermentation, while too little moisture can cause the leaves to become brittle.
In a withering trough, air is blown over or through the leaves using fans. The air temperature and humidity must be carefully monitored to ensure that the leaves wither at the right rate. If the air is too dry, the leaves can lose moisture too quickly, resulting in a poor-quality tea. On the other hand, if the air is too humid, the leaves may retain too much moisture, leading to a longer withering time.
Humidity is a critical factor in the withering process. The ideal humidity for withering tea leaves is around 70-80%, depending on the type of tea being produced and the climate. In some factories, hot air may be introduced during high-humidity conditions to increase the rate of moisture loss. However, the dry bulb temperature should not exceed 35°C to prevent damage to the leaves.
The depth of the leaf bed also influences airflow and moisture control. A deeper bed of leaves will take longer to wither, as the air may not reach the bottom layers as effectively. In contrast, a shallower bed allows for better airflow, leading to a more uniform wither. Factories often adjust the depth of the leaf bed based on weather conditions to optimize the process.
In summary, controlling airflow and moisture is essential for achieving consistent withering results. Tea factories must carefully balance these factors to produce tea leaves that are evenly withered and ready for the next stages of processing.