All tea begins life in the same way – as leaves on the Camellia Sinensis tea plant. Black tea is the name given to these leaves once they have been picked and left to oxidise fully, which is what turns them black and gives them their deep, intense flavour. There are lots of factors which can have an impact on the final product; the climate and soil in which the leaves are grown, what time of year they’re picked and how they’re processed will dictate flavour and mouthfeel.

While a lot of mass-produced black tea is grown and processed in Africa, high-quality black teas tend to come from China, India, Sri Lanka and Taiwan. India is home to familiar varieties such as Darjeeling and Assam, while Sri Lanka is renowned for its Ceylon and Earl Grey. Taiwanese black teas are very special, offering incredible flavours you’d never associate with the variety, whilst China grows and produces the biggest range of black teas in a huge variety of styles.

To fully oxidise a tea leaf and turn it into black tea, there are several processes that must be completed. The exact methods will vary from producer to producer and will differ depending on the style of black tea they are hoping to create.

Once a tea producer decides it’s time to pick the leaves, they will harvest them and begin the withering process. Once tea leaves are picked they will begin to wilt naturally, but producers control this by monitoring temperature, humidity and airflow. This removes moisture from the leaves and intensifies their flavour. This generally takes less than twenty-four hours.

Once the leaves have withered to the point a tea producer is aiming for, it’s time to roll them. This can be done by hand or by machine, but the aim is to twist and break each leaf so the remaining moisture is released. This kickstarts the oxidisation process and gives the leaves their twisted, curled appearance. Some tea producers crush or cut leaves rather than roll them to change the leaves’ characteristics. Releasing the moisture in this way turns the leaves a darker green, and they begin to clump together and take on a thin, spindly appearance.

Rolled, crushed or cut leaves will begin to break down in their own natural juices, a process known as oxidisation. This is arguably the method which has the biggest effect on a tea leaf, and black teas are left to oxidise longer than any other style. The rolled leaves are spread out onto large trays and kept at a warm temperature and specific humidity. As the broken down leaves react with the oxygen in the air, they begin to darken in colour – much like when you bite into an apple and it starts to turn brown over time. Oxidisation also changes the flavour and aroma of the tea leaves; as a general rule, the longer the leaves are left to oxidise, the more tannic, brisk and ‘strong’ they will taste.

When the tea producer believes the tea has oxidised fully, it’s time to dry the leaves ready to be packed, stored and sold. Some specialist black teas are shaped before being dried, but most are left in their natural state. The drying process does two things; it stops oxidisation by removing the excess moisture and dries the tea out enough so that it can be stored and kept for longer. When it comes to black tea, this final blast of heat turns the already brown oxidised leaves even darker into the black strands we pour boiling water over.

While there is one general method for creating black tea, lots of different factors in the growing, harvesting and processing will result in wildly different flavours, colours and mouthfeel in the final cup. Here are some of the most popular and interesting black teas out there.