Why Red tea goes wrong
Red tea, sold as black tea in the West, is the most forgiving category and still gets ruined regularly. The reasons are almost always dose and time rather than temperature.
Because the leaf is fully oxidised it gives up everything it has quickly. That is convenient, and it also means the gap between right and overdone is shorter than people expect.
The two mistakes below are the common ones, and they pull in opposite directions, which is why advice on red tea sounds contradictory.
Too much time brings astringency. Too little leaf gives a thin cup. Fixing the first by changing the time makes the second worse.
Separating the two is the whole skill.
Leaf grade plays a part too. Broken grades such as those used in tea bags extract far faster than whole leaf, and two minutes is plenty for them.
Mistake 1: over-steeping into astringent bitterness
Astringency is not the same as strength. It is a drying, puckering sensation from tannins, and it arrives once the leaf has given up everything useful and keeps going.
Four minutes at 95 degrees is about the limit for a Western brew of 5 grams in 200 millilitres. Six minutes is reliably harsh.
The usual cause is not the clock, it is the leaf staying in. A pot with the leaf still in it is still brewing whatever the timer says.
Decant, or lift the basket out. That single action prevents most bad red tea.
If you want a stronger cup, add leaf rather than time. An extra gram gives body without the drying finish.
The gaiwan method sidesteps the problem. Five grams in 120 millilitres, 15 second steeps, and it runs six or seven rounds without turning harsh.
Water at 95 rather than 100 is a small improvement for most red teas. It costs nothing to wait 30 seconds after the kettle switches off.
Warm the pot first. A cold ceramic pot drops the water by 5 to 10 degrees the moment you pour, which shortens your window without you noticing.
Mistake 2: too little leaf so the cup tastes thin
The opposite failure is more common in the West, because a teaspoon per mug is the habit most people learned.
Two grams in 300 millilitres will never produce a satisfying cup, however long you leave it. The liquor tops out at coloured water.
Red tea needs 5 grams per 200 millilitres for a Western brew, and about 1 gram per 15 millilitres for a Chinese one.
Weigh it for a week and you will recognise the amount by eye afterwards.
If you take milk, the dose matters more rather than less. Milk covers a weak brew rather than fixing it, and the result is a bland, cloudy cup.
Hard water makes this worse. Above about 150 parts per million of dissolved solids the liquor turns flat and dark, and a filter jug is a cheaper fix than better tea.
Blends behave differently from single origins. A breakfast blend is designed to survive boiling water and milk, and a first flush Darjeeling is not.
If you use bags, use two. A single bag holds roughly 2 grams, and it was sized for a small cup rather than a mug.
The habit that prevents both
Fix the dose first and leave it there. Five grams per 200 millilitres for a pot, or 5 grams per 120 millilitres for a gaiwan.
Then use a timer and remove the leaf. Those two together cover almost every failure.
Taste at three minutes rather than five. You can always pour later, and you cannot undo an over-brewed pot.
If the tea is astringent, shorten the time. If it is thin, add leaf. Never do both at once, or you will not know which one worked.
That is the habit: a weighed dose, a timer, the leaf out on time. Red tea asks for very little beyond that.
Keep a note of the dose that worked and reuse it. Red tea is the category where this pays off fastest, because the variables are few.
A cold mug is the other quiet problem. Pour 95 degree water into one and it arrives closer to 80, which is below what a red tea needs to open.