Assam reaches the cup by two roads, and this office certifies both. CTC, short for crush, tear, curl, runs the leaf through toothed rollers until it comes out as small hard granules that brew fast, dark, and brisk, and take milk without flinching. Orthodox rolls the leaf gently and keeps it largely whole, which brews slower and gives a cup with more range. Look at the grade in the tin and you already know most of what the brew will do. That is the whole answer. The rest is why, and when to reach for which.

CTC: crush, tear, curl, and where it came from

CTC is the modern workhorse, and it is an Assam invention. The first CTC machine was built in Assam in the early 1930s, credited to William McKercher, then superintendent of the Amgoorie Tea Company, who invented the machine to do by toothed roller what orthodox rolling did slowly by hand, World Tea News reports. It crushes, tears, and curls the leaf into tight pellets instead of rolling it whole, and the method went on to spread through India and East Africa until it became how most of the world's black tea is now made.

The point of all that crushing is surface area. A torn cell wall oxidises faster and gives up its colour and strength faster in the pot, so CTC brews dark and brisk in a couple of minutes and stands up to a hard splash of milk. The great majority of Assam is made this way, and almost every robust tea bag and every proper builder's brew depends on it. If you want strength, speed, and a cup that punches through milk, CTC is the honest answer.

Orthodox: the whole leaf kept whole

Orthodox processing is the older road. The leaf is withered, rolled gently to bruise rather than shred it, oxidised, and dried, and it comes out as twisted whole-leaf strips rather than granules. It brews slower because the cells are less broken, and it rewards the wait with more in the cup: the malt is still there, but around it sit depth, a little sweetness, and the golden tips that mark the better lots. Orthodox Assam is the one to drink without milk, or with only a little, when you want to taste what the garden actually grew. Reach for the second flush if you can find it.

Why the two cups taste different: the chemistry

The split in flavour is not mystery, it is oxidation. When the leaf is bruised, an enzyme turns its catechins into two families of coloured compounds. Theaflavins are bright and golden and carry the briskness and the bright edge of the cup. Thearubigins are orange-brown and carry the body, the thickness, and the deep colour. In a finished black tea, theaflavins run to roughly 0.5 to 2 percent of dry weight and thearubigins to roughly 6 to 18 percent, according to the Tea Research Association at Tocklai, Assam's own tea-science institute.

CTC's hard crush ruptures far more cells far faster, which drives oxidation hard and pushes the cup toward strong colour and a brisk, coloury liquor that reads through milk. Orthodox's gentler roll keeps more of the leaf intact, so oxidation runs slower and more of the leaf's aroma compounds survive instead of being driven off. A study of CTC processing on North East India leaf, published in RSC Advances, tracked the catechins falling as the rollers did their work, which is the chemical signature of that hard, fast oxidation. So the two methods are not better and worse. They are tuned for different ends: CTC for strength and speed, orthodox for range.

The surprise on the shelf: the minority method wears the badge

Here is the part most drinkers have backwards. CTC is the overwhelming majority of what Assam makes, and orthodox is the minority. Assam turns out around 85 million kilograms of orthodox tea a year against a total crop of more than 700 million kilograms, the Assam Tribune reports, so the great bulk is made as CTC. You would expect the dominant method to be the protected one. It is the other way round: it is whole-leaf orthodox, not CTC, that carries Assam's registered Geographical Indication and the state subsidy that comes with it, the legal badge sitting on the minority crop rather than the bulk one.

The reason is the export market. A large share of Assam's orthodox crop goes abroad, with Iran one of its biggest single buyers, taking close to a third of the orthodox crop. That exposure cuts both ways. As of June 2025, when the war between Iran and Israel threatened the shipping route, former Tea Board chairman Prabhat Bezbaruah warned that the orthodox price, which had climbed to Rs 50 to 60 per kg (about 60 to 70 US cents), had already dropped by about Rs 100 a kilogram in the market, the Assam Tribune reported. So the cup you can buy cheapest at home is the one with no protected name, and the one the region works hardest to make is the one most likely to leave the country.

Leaf grades, decoded

Each road carries its own grade code, and both describe leaf size and tip, not flavour. Orthodox runs the lettered orange-pekoe ladder, from OP whole leaf up through the tippy TGFOP to FTGFOP and finer, where more golden tip means a smoother, maltier lot; CTC carries its own short size codes instead. This office keeps the full grading bench, every letter, size, and CTC code read in order, for when a packet needs decoding.

Which to reach for

Reach for CTC when you want a strong, brisk, everyday cup that takes milk, the kind that runs a household. Reach for orthodox, second flush if you can find it, when you want to sit with the tea and taste the valley. This office keeps both on the shelf and judges neither for being what it is: two honest answers to two different questions.

Sources

1. Assam Celebrates 200-Year Tea History, World Tea News, on William McKercher inventing the first CTC machine in Assam.
2. Bio-chemical Index of Tea Color, Tea Research Association (Tocklai), on theaflavins, thearubigins, and their dry-weight ranges and sensory roles.
3. Changes in major catechins, caffeine, and antioxidant activity during CTC processing of black tea from North East India, RSC Advances, 2021, on how CTC processing drives catechin oxidation.
4. Registered Geographical Indications of India, Geographical Indications Registry, Intellectual Property India, which lists Assam (Orthodox) as a registered GI (application 115).
5. Iran-Israel conflict puts Assam's orthodox tea exports at risk, says expert, Assam Tribune, June 24, 2025, on orthodox volume, the Iran market, and Prabhat Bezbaruah's June 2025 price warning.
6. Scheme to boost orthodox, specialty teas: 378 Assam tea estates get incentives, The Shillong Times, on the 2025 Assam incentive scheme for orthodox tea.