Two words doing one job
"Strong" in ordinary use means two different things and the confusion is the whole problem. STRENGTH, properly so called — how much dissolved material sits in a given volume of liquid. This is set principally by the LEAF-TO-WATER RATIO. More leaf in the same water gives a denser cup, and nothing else raises that ceiling. EXTRACTION — what proportion of the available material has come out of the leaf. This is set by time, temperature, agitation and how broken the leaf is. A reader who wants a stronger cup almost always means the first of those. Extending the steep raises extraction, and lifts the amount of dissolved material only slightly — so it delivers a little of what was wanted and a great deal of what was not.
The order things come out in
TeaHQ's own reading of well-attested general knowledge, with no single source behind it.
Extraction is not uniform. Different compounds leave the leaf at different rates, and that ordering is why time changes character rather than just intensity. EARLY, in the first thirty seconds to a minute or so: caffeine, amino acids and the smaller aromatic molecules. This is why a very short steep can taste sweet, savoury and aromatic and still feel thin. MIDDLE: the bulk of the catechins and polyphenols, which carry astringency and body. LATE: the larger, more slowly diffusing polyphenol fractions, which are where harsh astringency and flat bitterness live. So a long steep does not give you more of the same cup. It gives you a cup with a different balance, weighted toward the fractions that arrive last, and those are the least pleasant ones.
Why a long steep also loses aroma
The aromatic compounds are volatile, which is what makes them smell of anything. A pot left standing for five minutes has been evaporating them the whole time, and a great deal of what you would have smelled has left the liquid. That is the mechanism behind a common and confusing complaint — a tea that smells wonderful in the packet and tastes of very little. Over-steeping is one of the two usual causes; the other is stale leaf, where the aroma had already gone before brewing started. It is also why covering the pot matters more than it looks, and why a tea poured off promptly reads as more aromatic than the same tea left to sit.
What to change instead, in order
IF IT IS TOO WEAK: add leaf. Go up by a third and taste again, keeping the time the same. This is the change most people never make and it is almost always the right one. IF IT IS BITTER AND ASTRINGENT: shorten the time, then lower the temperature. Both reduce extraction; time is the blunter and quicker instrument. IF IT IS THIN BUT HARSH — the worst combination and a common one: you have too little leaf and too long a steep. Raise the leaf and cut the time together. This single adjustment fixes more disappointing cups than any other. IF IT IS FLAT: the tea is probably stale, and no brewing parameter recovers aroma that is gone.
Why the gongfu method exists
The Chinese small-pot method is this principle taken to its conclusion: a very high leaf-to-water ratio with very short steeps, often fifteen to thirty seconds, repeated many times. That combination gives a dense cup — plenty of leaf — with low extraction per infusion, so each pour is intense and none of it reaches the harsh late fractions. Then the leaf is used again, and the schedule lengthens as the easily extracted material is exhausted. Western brewing makes the opposite trade: little leaf, long time, one infusion, drawing out nearly everything at once. Neither is superior; they are different points on the same two axes, and knowing which axis you are moving is the whole of the skill.
The exception that proves it
Cold brewing steeps for hours and does not turn bitter, which looks like a contradiction and is not. Temperature is doing the work. Cold water extracts the astringent and bitter fractions very slowly and the sweeter, more aromatic ones comparatively better, so a twelve-hour cold steep can sit at a low overall extraction of exactly the parts you want. Time alone is not the villain; time at temperature is.