Bands rather than points
Brewing advice is usually given as a single figure, which implies a precision that nothing about domestic brewing supports. A kettle that has stood for two minutes, a cold pot, a cold room and a slow pour can easily put fifteen or twenty degrees between the stated temperature and the water actually in contact with leaf, and none of those variables is on the packet. Thinking in bands is both more honest and more useful, because the transitions between them are gradual and the differences within any one of them are small enough to disappear under the noise. What follows describes what each band is doing, so that a reader meeting an unfamiliar tea can reason about where to start rather than searching for a rule. The bands themselves are a convention of this catalogue and not a natural division: nothing changes abruptly at any boundary, and a tea brewed at the top of one band and the bottom of the next will taste almost identical. The value of the scheme is that it names the intention behind a temperature choice, which a bare number never does, and intention is the thing that transfers to the next tea.
Below about sixty degrees: selection rather than extraction
At the bottom of the usable range the water is taking out the readily soluble sweet and savoury fraction and very little else. The material associated with astringency dissolves so slowly at these temperatures that even a long steep leaves most of it in the leaf, which is what makes this band a selection tool rather than a gentle version of ordinary brewing. Time does not substitute for heat here in the way the intuition suggests: an hour at fifty degrees does not reach the same place as three minutes at eighty, it reaches a different place, and that is the entire reason the band exists. The cost is volume and body. What comes out is intense, small, syrupy and quite unlike a cup of tea, which is why the vessels used are tiny and the servings are mouthfuls. It only makes sense with leaf that has an unusual amount of the sweet fraction to select for — shaded Japanese tea above all, and to a lesser extent very fine bud material — because applied to ordinary leaf the result is not sweet, it is simply weak, and the reader concludes that low-temperature brewing is a myth.
Sixty to seventy-five: the Japanese green band
Here there is enough energy to produce a full cup and still not enough to bring the harsher fraction across in quantity. This is where most Japanese green tea is brewed, and the reason is compositional rather than cultural: steaming ruptures the leaf structure thoroughly, so a steamed leaf gives up its solubles readily and the water does not need to be hot to extract enough. Shading, where it has been used, raises the sweet fraction that is worth protecting, and the two together make the low band both possible and worthwhile. The characteristic failure at this band is not bitterness but thinness, and it appears when the band is applied to leaf it was not developed for. A Chinese pan-fired green tea brewed at Japanese temperatures is routinely disappointing, and the disappointment gets attributed to the leaf or the seller rather than to a fifteen-degree mismatch. The band is also unforgiving of a cold pot, because there is so little margin: water at seventy degrees poured into a cold vessel is not at seventy degrees for long, and preheating matters more here than anywhere else in the range.
Seventy-five to eighty-five: most Chinese green and delicate white
Pan-firing seals and hardens the leaf surface more than steaming does, so Chinese green tea generally wants more heat than Japanese green tea to give the same amount — the same structural difference that makes the two behave differently in cold water. This band also suits fine white tea, though white tea is routinely brewed far cooler than it wants on the assumption that pale, downy leaf must be delicate. It is not: white tea is minimally processed rather than fragile, and its usual fault at home is under-extraction rather than harshness. The visible sign of being at the right point in this band is a liquor with weight as well as fragrance, and a finish that continues after the swallow. The sign of being too low is a cup that smells right and tastes of almost nothing, which is by some distance the most common fault with good green tea in domestic brewing and one of the most frequently misdiagnosed — the usual response is to steep longer, which adds the later fraction to a cup that was missing the earlier one and makes it worse.
Eighty-five to ninety-five: oolong, black and the working compromise
This is where most of the world’s tea is made, and it is a wide band rather than a point because it spans genuinely different intentions rather than one intention with a tolerance. Lightly oxidised and floral material sits at the lower end, where aromatics come off readily without dragging much of the tannic fraction with them, and where a few degrees too many audibly coarsens the fragrance. Ordinary black tea sits at the upper end, where enough is extracted in a single steep to make a full cup that will carry milk and still taste of something. The band is also where the practical compromise lives for anyone brewing without temperature control: water taken off the boil and rested for a minute or two lands somewhere in here, and it is a defensible default for a tea you know nothing about. If a single band had to be chosen for a whole cupboard, this would be it, which is why so much English-language brewing advice collapses to it and why that advice works tolerably well for the teas it was written about.
Ninety-five and above: roast, compression and fermentation
The top of the range is not a stronger version of the band below it, and treating it that way is the source of a great deal of confusion. Full-boil water is needed by materials that will not open otherwise: heavily roasted oolong, compressed dark tea, aged leaf of any kind, and anything whose defining aromatics only volatilise near the top of the scale. For those, water that has fallen even a few degrees gives a thin, sour, closed cup, and the failure mode is under-extraction rather than gentleness — the tea tastes wrong rather than weak, which makes it hard to diagnose. This is also the band where heat retention in the vessel starts to dominate the kettle setting, because the temperature gradient to the room is largest exactly where the tea can least afford any loss. A thin porcelain gaiwan filled with boiling water is well below boiling within seconds, which is why clay, preheating and working quickly all matter more here than they do at seventy degrees, and why the same tea can seem transformed by a change of vessel.
The bands belong to the leaf, not to the category
The pattern that makes all of this hang together is not oxidation level, not colour and not the name of the category. It is how much physical resistance the material offers to being wetted, and how much of what it has to give is heat-sensitive. A rolled, roasted oolong and a compressed dark tea want the same water for the same reason despite sitting in different categories on the shelf; a shaded Japanese green and a fine white bud tea diverge sharply despite both being minimally processed. When meeting a tea with no instructions, the three questions that predict the band are how tightly the leaf is furled, how hard it has been fired, and how much of what it offers is fragrance rather than body. Those can all be answered by looking at and smelling the dry leaf before any water is boiled. It is a better heuristic than the category rule because it is about the object in front of you, and because it does not collapse when the tea is something the category rule never anticipated.