5 September 2026 · 4 min read
good coffee isn't magic or an expensive machine. it's managing a few simple variables. once you understand extraction and ratio, you can fix almost any cup deliberately instead of blindly trying «let's do it again».
what extraction is
when water meets ground coffee it pulls compounds out in turn, in a certain order: first the acids and the fruity, salty notes; then sweetness and balanced flavours; and last the bitter, woody and astringent ones. under-extraction — you stopped too early and took only the «first wave»: the cup is sour, sharp and hollow. over-extraction — you took too much and reached the «last wave»: the cup is bitter, dry, astringent. the goal is to land in the sweet middle, where there's acidity, sweetness and body all at once.
the golden ratio
the baseline for filter is roughly 1 part coffee to 15–17 parts water by weight. so about 240–250 ml of water for 15 g of coffee. espresso runs a different, more concentrated ratio — about 1 to 2 (18 g of coffee yields around 36 g of drink in ~25–30 sec). the key word is WEIGH, not eyeballing or «spoonfuls»: a cheap kitchen scale changes the game more than any trendy gadget, because it makes the result repeatable.
the three levers you control
there are really only three variables, and all of them push extraction the same way:
- grind: finer = more surface area = faster and stronger extraction (details in a separate article)
- contact time: longer in the water = stronger extraction
- water temperature: hotter = stronger extraction, aim for 90–96°c (lighter hotter, darker cooler).
how to fix a cup (an algorithm)
first make the diagnosis by taste, then turn a lever:
- sour, sharp, «hollow» (under-extracted): grind finer, or extend the time, or raise the temperature
- bitter, dry, astringent (over-extracted): grind coarser, or cut the time, or lower the temperature a touch
- weak/watery (too little coffee) or too strong (too much): change the RATIO, not the grind.
the golden rule: change ONE thing at a time — otherwise you won't know what worked.
water temperature without a thermometer
if you have no thermometer: boil the water and let it sit for ~30–45 seconds — it drops to about 92–94°c, near ideal for most coffee. boiling water straight off the boil more often scorches light beans and adds bitterness.
consistency beats «perfect»
don't chase perfection first. make the process REPEATABLE first: the same weight of coffee, the same grind, the same water, the same time. once the baseline cup is stable you start to hear the subtle changes and can chase them on purpose. that's when brewing turns from roulette into a pleasure, and the result stops depending on your mood and the phase of the moon.