There are brown stains inside my teapot and cups

In short

Mostly cosmetic, and worth knowing which parts are cosmetic and which are not. On glazed and glass ware the stain is harmless and removable; on unglazed clay it is the seasoning the vessel exists for and should be left alone.

Likely causes, in order

Most likely first. Answer the question under each one before moving on — several of these look alike in the cup and are told apart only by what was done to the leaf.

1. 1. Ordinary tannin staining on a glazed surface

   Equipment

   Check: Is the vessel glazed porcelain, glass or steel?

   Fix: Cosmetic rather than a fault. Bicarbonate of soda on a soft cloth removes it; scouring a glaze or scratching glass is unnecessary and permanent.

2. 2. Patina on unglazed clay

   Equipment

   Check: Is it an unglazed clay pot or cup?

   Fix: Leave it. That layer is the seasoning the pot is kept for, and removing it undoes years of use. Hot water only, and never detergent.

3. 3. Hard water accelerating the deposit

   Water chemistryInferred by TeaHQ, not established

   Check: Does the stain build within days rather than months?

   Fix: Hard water leaves a combined mineral and tannin film that forms much faster than tannin alone. Filtered water slows it noticeably and improves the tea at the same time.

4. 4. Leaf or liquor left standing

   Technique

   Check: Is wet leaf regularly left in the pot for hours?

   Fix: Empty and rinse after the session. Standing liquor stains far faster than brewing does, and wet leaf left overnight in a warm room causes a separate problem.

Tea types this applies to

• Black tea

Brewing methods this applies to

• Western brewing (teapot or mug) — A small amount of leaf in a large volume of water, steeped once for a few minutes and then strained off. The approach most English-speaking drinkers already know, and the one most teas sold in the West are made for.
• Gongfu brewing (Yixing pot) — The same short-steep, high-leaf approach as gaiwan gongfu, carried out in a small unglazed clay pot that seasons over time and is dedicated to one tea.

Guides covering this

• Foam, film and the surface of the liquor — Three quite different things appear on the surface of a cup of tea — a foam, an oily film and a dull scum — and they have unrelated causes. Two are properties of the leaf and one is a property of the water.

Related problems

Sharing a cause category, a tea type or a brewing method with this one.

• My tea goes cold before I finish it — The cup is lukewarm within a few minutes, and in a gongfu session the later infusions arrive noticeably cooler than the early ones.
• There are black spots inside my teapot or infuser — Dark speckling inside a spout, under a lid seal, in the mesh of an infuser or around the gasket of a travel bottle.
• There is an oily film on the surface of my tea — An iridescent or dull skin sits on the surface of a cup or pot, breaking into patches when disturbed and clinging to the side as the level drops.
• My milk curdles or separates in the tea — Flecks or threads appear when the milk goes in, or the surface breaks into small islands, and the drink looks grainy rather than smooth.
• My tea gets drier and harsher as it cools — The first mouthful is balanced and the last one, several minutes later, grips the tongue and feels rough — from the same cup, with nothing added.

Sources