Sorting and grading

Separating dried tea by particle size, density and colour into the grades it is sold as — a sorting operation, not a quality judgement.

篩分Stage 7 of 13: Rolling and shapingAlso called siftingAlso called winnowingAlso called leaf gradingAlso called cleaning

What it is

Everything that comes out of the drier is a mixture. Sorting passes it over a stack of vibrating mesh screens that split it by size, through a winnower that lifts out light material such as fluff and fibre by airflow, over a magnetic or electrostatic stemmer that pulls out stalk, and increasingly under an optical sorter that ejects individual pieces by colour. What emerges are the named grades — the whole-leaf, broken, fannings and dust classes of the orthodox vocabulary, and the BP, PF, PD and Dust classes of CTC. Every one of those names describes particle size and therefore extraction speed. None of them describes how the tea tastes, and a factory can produce an excellent whole-leaf grade and a poor one on the same day from the same batch.

Also transliterated as: shai fen, shaifen.

What it does to the leaf

Separates finished leaf into fractions by size, density, colour and magnetic response, removing stem and foreign matter and producing uniform, tradeable lots.

What it does to the cup

Acts on extraction rate rather than on composition: smaller fractions from the same batch brew faster, stronger and more astringent than larger ones.

Variants that matter

Ways this step is carried out that produce genuinely different results, rather than regional names for the same thing.

Screen sifting: Stacked vibrating meshes of decreasing aperture. The basis of every orthodox grade name in the trade.
Winnowing: An air stream lifts light fibre and leaf hair out of the stream. What it removes is why a well-finished tea does not fill the packet with dust.
Optical sorting: Cameras and air jets eject pieces outside a colour tolerance, chiefly stem and yellowed leaf. Now standard at scale and increasingly used on speciality lots.
Hand sorting: Still used at the top of the market, where a person picks stalk and off-colour leaf from a tray. Slow, and the only method that can judge more than one attribute at once.

Where this gets misdescribed

Grade names are read as quality tiers, so a tea labelled as a broken grade is assumed to be inferior to a whole-leaf one. They are sieve sizes with some tip-content vocabulary attached. The letters tell a buyer how fast the tea will brew and how it will look in the cup, and say nothing at all about the garden, the season or the skill of the manufacture.

Other steps at the Rolling and shaping stage

Blending to a standard — Combining lots so that a named tea tastes the same in March and in October, which is a manufacturing step performed on finished tea and not a compromise applied to it afterwards.
Cloth-ball rolling — Wrapping leaf tightly in cloth and repeatedly kneading and unwrapping it until it forms tight spheres.
CTC (crush, tear, curl) — Leaf passed through counter-rotating toothed rollers that cut it into small uniform granules.
Curling and down-raising (cuo tuan xian hao) — Rubbing warm leaf between the palms into loose balls and breaking them apart repeatedly, which curls the leaf into spirals and lifts its down to the surface.
De-stemming and de-veining — Separating stem and leaf vein from the leaf blade after drying, usually by air separation.
Flat shaping — Pressing leaf flat against the side of a heated wok by hand during pan-firing.
Needle shaping (li tiao) — Shaking fixed leaf along heated parallel grooves until each piece straightens into a needle, rather than twisting it into a curl.
Orthodox processing — The older manufacturing route, in which leaf is twisted and rolled rather than cut, so it survives largely intact.
Pearl forming (chao gan cheng yuan) — Working rolled leaf against the wall of a heated pan through successive pans until each piece closes into a hard sphere, drying and shaping in the same operation.
Refining (shiage) — The second factory. Japanese green tea leaves the producer as aracha, an unfinished trade good, and is cut, sorted and separated elsewhere into the several named teas one intake contains.
Repeat rolling and roll-breaking (fu rou) — Rolling is done in two or three passes with the compacted lumps broken up and sifted between them, because one long pass tightens the outside of a ball of leaf and never reaches the middle.
Rolling and shaping — Working the leaf to rupture its cells and give it a form that governs how it later brews.
Rotorvane maceration — A screw press with internal vanes that macerates withered leaf continuously, sitting between orthodox rolling and CTC rather than belonging to either.
Stalk picking (jian ti) — Hand removal of stalk and yellow leaf from finished oolong, done between roasts rather than at the end — which is why it is an ordering fact and not a tidying-up one.
Stone milling — Grinding de-stemmed tencha into powder between slow-turning granite wheels.
Strip rolling — Rolling leaf into long twisted strips rather than compressing it into balls.

Guides covering this step

How one machine changed the world tea trade — Crush, tear and curl was a manufacturing change that turned into an economic one. It made tea cheap, strong, fast-brewing and suitable for a bag, and in doing so it decided what most of the world means by the word tea.
What happens after the drier — In several traditions a tea is not finished when it comes out of the drying machine. Sorting, refining, final firing, blending and resting are real operations, they are frequently performed by a different business, and they can move a tea further than anything the grower did.

Sources

TeaHQ editorial synthesis — TeaHQ

This page is TeaHQ’s own synthesis of well-attested production practice. No external technical document stands behind it, so it describes what producers do rather than asserting measured process parameters.

How TeaHQ handles sources

Written comparisons

Where TeaHQ has set this step against something it is routinely confused with, and argued the differences out in full.

Sorting and grading vs de-stemming — Two separation steps that between them produce almost every grade name a drinker will ever read, and neither is a quality judgement. Sorting separates finished leaf by size and density; de-stemming separates stem and coarse vein from the blade.