Time
Every method is a clock with an opinion — 4 min
Contact time is how long water and coffee actually touch: about thirty seconds for espresso, two and a half to three and a half minutes for a pour-over, four to nine for a press, half a day for cold brew. Each method's grind is chosen to suit its clock — coarse for long, fine for short.
Here is the subtlety: in immersion brewing, time is a decision — you choose when to press. In percolation, time is a consequence — the grind and your pouring set how fast water drains, and the clock merely reports it. When a pour-over runs long, the fix is the grind, not the timer.
Interactive
Drag along a press steep — notice how much the first minutes do and how little the last ones add.
Try it in the Blend app
Extraction is front-loaded. The first minute does more work than the next three combined; every added minute contributes less than the one before. That curve is why a press forgives a late plunge — thirty extra seconds near the flat end of the curve barely moves the cup — and why espresso punishes the same thirty seconds, which near the steep start is half the brew.
So treat time as the honest witness of the other variables: when it drifts far from the recipe, something upstream — usually grind — moved first.
Note
Two brakes slow a long steep: the brew approaches saturation, and it cools — both flatten the curve. That is why an immersion brew slides gently rather than falling off a cliff, while percolation, constantly fed with fresh hot water, keeps climbing as long as you keep pouring.
Brew it with a guided timer.
Blend counts the pour, times every step, and saves what you change. Free on iOS and Android.