The conversion everybody attempts
Given a western parameter of a few grams in a couple of hundred millilitres for three minutes, and a gongfu parameter of several grams in a hundred millilitres for twenty seconds, the temptation is to read one as the other multiplied through: more leaf, proportionally less time. It looks like dimensional analysis and it produces a plausible number. It is wrong, and this codebase refuses to compute it — every tea in the catalogue carries a separately authored parameter set for each method it genuinely supports, precisely so that no tool can generate a confident answer by multiplication. A plausible-looking wrong answer is worse than no answer, because the reader has no way to tell it apart from a right one.
Rate is not completeness
The reason the arithmetic fails is that extraction does not proceed at a constant rate. It is fastest at the start, when the difference in concentration between the inside of the leaf and the surrounding water is greatest, and it slows as that difference closes. A twenty-second steep therefore does not extract one ninth of what a three-minute steep extracts; it extracts a much larger share than the time ratio suggests, because it captures the fast opening portion of the curve and none of the long slow tail. Halve the time and you do not halve the strength. This one fact undoes every proportional conversion anyone tries to build.
What a high ratio actually buys
With a great deal of leaf in a little water, a very short contact is enough to produce a full-strength cup. That has a consequence beyond convenience: because the leaf is only lightly worked each time, most of what it holds is still there afterwards. The same leaf can then be steeped again, and again, each time a fraction further along the extraction sequence than the last. The session becomes a series of samples through the tea’s range rather than one averaged result. A long single steep at a low ratio takes the average in one go, which is a perfectly good thing to want and is not the same thing.
The combination that is always wrong
High leaf and long time together is the one pairing with nothing to recommend it. It runs a heavily loaded vessel deep into the slow tail of the extraction curve, producing a liquor dominated by the grippy late fraction with the fast sweet fraction long since swamped. This is exactly what happens when someone tries gongfu for the first time, loads the vessel generously, and then steeps it for the two minutes they are used to. The first attempt at short-steep brewing is much better made too strong and too fast than too long: strong and fast is a cup you can dilute and learn from, and long is a cup that tells you nothing.
Why the vessel has to empty completely
A high ratio makes complete decanting non-negotiable in a way a low ratio does not. Liquid left behind in a heavily loaded vessel is both more concentrated and in contact with far more leaf per millilitre, so it goes on extracting hard between infusions and then joins the next steep as a head start nobody asked for. In a lightly loaded western pot the same residue is a minor dilution issue. This is why short-steep vessels are shaped to pour dry, and why the single most common fault in a gongfu session is not timing but a lazy pour.
What is established and what is convention
The non-linearity of extraction is a general property of the process rather than a claim about tea specifically: dissolution and diffusion driven by a concentration difference slow as that difference closes, which is why a short steep takes a disproportionate share. That much is solid. What is convention rather than physics is the particular ratios and schedules each tradition settled on. Those came from vessels, from the teas locally available and from centuries of adjustment, and they are worth following as starting points, not because a calculation produced them.