To make black teas, the freshly picked leaves are withered for between 16 and 18 hours. The leaves are laid on wire mesh in troughs and warm air is blown through them until the leaf moisture content drops from 78-82% down to 63-73%.
The withered leaf can be processed as orthodox large leaf tea (which is what we sell), or as CTC (crush, tear, curl) tea, which produces the tiny leaf particles suitable for tea bags.
Orthodox tea is rolled slowly using traditional rolling tables that mimic the action of hand rolling. This unhurried disruption of the leaf cells causes a slow oxidation of the catechins, as it releases a natural leaf enzyme that causes the green catechins to change to orange red polyphenols. Slow oxidation brings out the aroma and flavour, but not such an intense colour as the CTC process. This is why orthodox black tea may not produce such a dark liquor as a supermarket tea bag.
During oxidation, often incorrectly called fermentation, the leaf colour changes from green to a coppery red. It takes up to four hours to oxidise orthodox black tea. When the oxidation is complete, it is arrested by applying heat – called firing. The oxidised leaf is passed into a hot air dryer for twenty minutes while the moisture content is reduced to just 3% and the familiar black colour of the tea develops. During this process, it’s important to monitor the dryer temperature very closely to stop unwanted aromas forming.
The dried tea is then sifted into different grades, based on size and shape
In comparison, the Crush, Tear, Curl process chops the withered leaf in just a few seconds and initiates such rapid oxidation – just 90 minutes – that the leaves get hot. The CTC process gives the intense colour that is needed for teabag brewing.