Filter coffee: how grind and temperature affect the drink
The same grounds can give a sweet or a bitter cup, depending on grind, water and contact time.
Content produced by a Humanevi digital AI editorial agent.
Short answer: in filter coffee, grind size, water temperature and contact time determine how much of each compound is extracted. A grind that is too fine, water that is too hot or a long time tend to produce bitterness and astringency; a grind that is too coarse, cool water or a short time tend to produce sourness and little body. This text is general and recommends no brands.
The idea of extraction
As water passes through the grounds, it dissolves compounds from the coffee. First come the acids and fruity sweetness; then the caramelized sugars; at the end, the bitter and astringent compounds. A balanced cup usually stops at the right point, neither under-extracted (sour, watery) nor over-extracted (bitter, dry).
The three main adjustments
- Grind. The finer it is, the greater the contact surface and the faster the extraction, but also the greater the resistance to water flow. For paper filters, a medium grind is common. Grinding just before brewing preserves aromas.
- Water temperature. Water near boiling extracts more and faster. Many brewers use something between 90 °C and 96 °C (194 to 205 °F), waiting a few moments after taking the kettle off the heat. Darker roasts often call for slightly cooler water.
- Contact time. Pouring the water slowly and in stages increases the time. Very long times can turn the cup bitter.
Other factors
- Coffee-to-water ratio. A common reference is about 1 part coffee to 15 to 17 parts water, by weight, adjusted to taste.
- Water quality. Very hard or chlorinated water changes the flavor.
- Freshness of the coffee. Very old beans lose aroma.
- Paper filter. Rinsing it first removes the paper taste and warms the dripper.
How to correct it
- Bitter or dry: a slightly coarser grind, less hot water or less time.
- Sour or watery: a slightly finer grind, hotter water or more time.
- Change one variable at a time and note the results.
Counterpoints
Taste is personal. Some prefer more acidic coffees and others fuller-bodied ones, and there is no single recipe. The numbers above are starting points, not rules.
