How black tea is made: from leaf to liquor

Published 28 October 2026 · BluVira Exports, Kotagiri

Every black tea, from a fragrant Nilgiri orthodox leaf to a strong Assam dust, starts the same way: as two leaves and a bud plucked from a tea bush. What turns that soft green shoot into dry black tea, and decides whether the cup will be bright and fragrant or dark and strong, happens in the factory within about a day. This guide explains the process in plain words, for buyers who want to understand what they are tasting.

From leaf to liquor: six steps

1. Plucking fresh green leaf

   The young shoot, usually two leaves and a bud, is plucked and brought to the factory the same day. Finer plucking makes better tea.

2. Withering the leaf goes limp

   The leaf is spread in long troughs with air blown through it, usually for 12 to 18 hours. It loses water, turns soft and starts to build up aroma.

3. Rolling or CTC the cells are broken

   Orthodox factories twist the leaf in rollers and keep it largely whole. CTC factories cut, tear and curl it between toothed rollers into small granules. Either way, the leaf’s cells are broken open.

4. Oxidation green turns copper

   The broken leaf rests in cool, moist air, roughly an hour for CTC and two to three hours for orthodox. It turns from green to coppery brown. This is where the colour, strength and much of the flavour form.

5. Drying the browning stops

   Hot air dries the leaf for about 20 minutes, down to 2–3% moisture. The heat stops oxidation for good, and the leaf turns black.

6. Sorting into grades

   The dry tea is sieved by size into grades (whole leaf, broken, fannings and dust), then packed for the auction or for sale.

Green tea skips oxidation. The leaf is steamed or heated in a pan soon after plucking, which stops the browning before it can start. That is why green tea brews a pale, grassy cup.

“Fermentation” is really oxidation

In tea factories and at the auctions, step 4 is called fermentation, and a tea may be described as well fermented, under-fermented or over-fermented. The name is old and not quite right. True fermentation, as in curd or bread, needs yeast or bacteria. Black tea uses neither: the leaf browns through its own enzyme reacting with the air, just as a cut apple turns brown. Under-oxidised tea tastes raw and green; over-oxidised tea is soft, dull and flat. Stopping at the right moment is one of the tea maker’s main skills.

How the leaf turns brown

A fresh tea leaf is rich in natural compounds called catechins, a group of polyphenols. It also holds an enzyme, polyphenol oxidase, that can act on them. In the living leaf the two are kept in separate parts of the cell, so nothing happens.

Rolling or CTC breaks the cells open. The catechins and the enzyme mix, oxygen from the air joins in, and the catechins are turned into new coloured compounds:

• Theaflavins are golden-orange. They give the liquor its brightness and briskness, the lively, fresh bite that tasters prize. They make up only about 0.3–2% of the tea’s dry weight, yet they count for more in quality than almost anything else.
• Thearubigins are red-brown. They give most of the colour and body, the fullness in the mouth.

The more finely the leaf is broken, the more cells open and the more it oxidises. That is why CTC teas, and smaller grades in general, brew darker, stronger and faster than whole-leaf orthodox teas.

The compounds behind the cup

Black tea contains more than 300 aroma compounds, and they are delicate. Heavy cutting, over-oxidation, very hot drying and age all reduce them. This is why gently made whole-leaf teas tend to smell more fragrant, while CTC teas trade some fragrance for colour and strength.

Why grade size changes the cup

The size of the pieces changes the cup in two ways:

• In the factory: leaf that is broken finely before oxidation browns more, so it carries more colour and strength from the start.
• In the pot: smaller pieces expose more surface to the water, so everything comes out faster. Dust can colour a cup in a minute or two; whole leaf needs four or five.

Breaking the leaf after drying only does the second. Once the tea is dried the enzyme is inactive and no more browning can happen, so a crushed whole-leaf tea brews faster but does not gain the deep colour of a CTC tea. Brewing whole leaf for longer does not get there either; it mostly draws out more bitterness. For what each grade name means, see our guide to Nilgiri tea grades.

One plant, many bushes

All tea comes from one species, Camellia sinensis, which has two main types:

• China type (var. sinensis): a shrub with small, leathery leaves, hardy in cool climates. Its tea tends to be lighter and more aromatic.
• Assam type (var. assamica): a small tree with large, glossy leaves, at home in hot, humid lowlands. Its tea tends to be stronger and more coloury.

The two cross easily, so most gardens today grow hybrids. Many also plant clones: bushes grown from cuttings of one outstanding mother bush, so every plant in the field is the same. In South India, the UPASI Tea Research Institute at Valparai has released more than 30 clones, several of them selected from mother bushes in the Nilgiris, chosen for yield, drought tolerance or cup quality.

The place matters as much as the plant. Assam’s hot, wet plains produce fast-growing, heavy leaf that makes a dark, malty cup. In the Nilgiris, between about 1,000 and 2,500 metres, cooler air slows the growth of the leaf, and the tea comes out bright, brisk and fragrant. To see how this plays out around the world, read where the world’s tea grows, and why the Nilgiris stand out; for how the two Indian teas work together, see Nilgiri vs Assam tea for blending.

What tasters mean by “liquor”

In the tea trade, the liquor is simply the brewed tea in the cup. Tasters judge it separately from the dry leaf and from the infused leaf, the wet leaf left after brewing. When they assess a liquor, they look at:

• Colour and brightness: is it bright and clear, or dull and muddy? Many tasters also add milk to see the colour it gives.
• Strength and body: does it feel full in the mouth, or thin?
• Briskness: is there a lively, fresh bite, or is it flat?
• Flavour and aroma: are there sweet, floral or malty notes, or is it plain?

There is no single best liquor. A strong karak or chai needs colour and body that hold up in milk; plain tea and iced tea need brightness and fragrance. Choosing a tea means matching the liquor to the way your customers drink it.

BluVira Exports buys Nilgiri tea at the Coonoor auction and directly from factories and estates, and tastes every lot against the buyer’s approved sample. See our Nilgiri tea range or download the tea specification sheet (PDF).