Tea sock (cloth filter bag)
A long cloth bag on a wire hoop, used in Hong Kong tea houses and across South East Asia to hold and strain a strong tea brew, with the liquor poured through it repeatedly. It is called a stocking because that is what it comes to look like, stained deep tan by use; no stocking is involved.
Identity
- Category
- Filter or infuser
- Native name
- 茶袋
- Romanised
- cha doi, cha dai
- Also called
- silk stocking filter, cloth tea strainer, flannel bag
- Material
- Cotton flannel, muslin or a similar close-woven cloth on a wire frame
- Typical capacity
- 200–1000 ml
- Skill level
- Intermediate
Porous — this changes how it is used
Porous. It takes up a trace of every tea brewed in it and gives some of that back to the next, which is why such a vessel is kept for one tea rather than shared across a shelf.
Cloth holds oils and fine particles in its weave, which is why a bag in daily use is dedicated to one blend and why the weave keeps back material that an open metal mesh passes straight into the cup. That retention is the physical fact. Cloth-strained tea is very widely described as rounder in the mouth than the same tea through metal, and the practice is built around that description, but TeaHQ has not found a controlled comparison establishing the size of the difference — or even which direction the retained material pushes the result — and does not assert one.
Where it comes from
Hong Kong tea houses above all, with parallel cloth-filter practices in Malaysia, Singapore and Thailand.
Named here rather than presented as generic equipment. The object belongs to a practice, and TeaHQ describes it from the outside.
If you do not own one
A fine metal strainer catches the leaf and none of the rest. A double layer of muslin over a jug is much closer to the real thing than any mesh.
This one is not marked essential. The tea can be made without it.
Brewing methods it is used for
- Hong Kong milk tea (sock-strained) — A blend of black teas brewed very strong and passed repeatedly through a long cloth filter between two pots, then finished with evaporated milk. The filter stains to a deep tan with use, which is where the popular name comes from — there is no stocking involved.
- Chai preparation — Tea simmered with milk, sugar and whole spices rather than steeped — a decoction, and the daily preparation of a very large part of the world. There is no single authoritative recipe, and regional and household variation is enormous.
Tea types it suits
Care and maintenance
Rinse in hot water only and store it wet in clean water or dry it completely — the two failure modes are detergent, which the cloth holds and returns to the next batch, and a damp bag left folded, which sours. Never bleach it.
Other filter or infusers
Sources
This page is TeaHQ synthesis. No external source stands behind the description, the material or the account of how the object is cared for. Where the record names a tradition, that attribution is TeaHQ’s own reading of common practice rather than a citation.
TeaHQ names no maker, brand or shop and has nothing to sell. Nothing on this page should be read as advice to buy the object — the substitute note above exists because owning it is usually optional.
Written comparisons
Where TeaHQ has set this piece of teaware against something it is routinely confused with, and argued the differences out in full.
- Tea sock vs mesh strainer — A cloth filter bag on a wire hoop against a metal mesh held over a cup. Both separate leaf from liquor and the cloth does something else besides: it is used to pour the brew through repeatedly, which is the technique behind Hong Kong milk tea’s smoothness.