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Home Coffee Brewing

Water quality, temperature and brew ratios

The often-ignored variables: brewing water mineral content, temperature for different methods, and standard ratios for pour-over and immersion.

By Cameron Marsh ·

Coffee is more than ninety-eight percent water by weight. Whatever flavour and texture is in your tap also goes into the cup. Most home brewers ignore water until they switch to a different source and notice their coffee suddenly tastes different — usually worse.

What makes water good for coffee

The Specialty Coffee Association publishes a target water profile: around one hundred and fifty parts per million of total dissolved solids, with a balance of calcium and magnesium for extraction, low sodium, no chlorine, and a neutral pH. Most municipal tap water is too hard, too soft, or too chlorinated to brew clean coffee.

The cheapest fix is a charcoal filter pitcher — it removes chlorine and reduces hardness. The next step up is a refillable filter cartridge in your kettle. Anything more involved (remineralised distilled water, third-wave water packets) is a project for people who have already optimised everything else.

Temperature

The standard target is between ninety-two and ninety-six degrees Celsius. Hotter water extracts more — both the good compounds and the bitter ones. Cooler water under-extracts and leaves the cup sour and weak.

For dark roasts, brew cooler — around ninety degrees — because the roasting has already broken down the cell structure and bitterness comes out fast. For light roasts, brew hotter — closer to ninety-six — because the dense beans need more energy to extract fully. If you cannot tell whether it is the temperature or something else, see bitter or sour brews.

Without a temperature-controlled kettle, boil the kettle and let it sit for thirty seconds before pouring. The water will have dropped about three degrees. For an espresso machine, the boiler regulates this for you.

Brew ratios

Ratios are coffee weight to water weight, both in grams. Standard ratios:

  • Pour-over (V60, Chemex) — 1:15 to 1:17, with 1:16 a safe starting point
  • French press — 1:15
  • AeroPress — 1:14 to 1:18 depending on recipe
  • Drip machine — 1:17 to 1:18
  • Espresso — 1:2 (eighteen grams in, thirty-six out)
  • Cold brew concentrate — 1:5 to 1:8, diluted to taste before serving

Within a ratio, smaller numbers mean stronger coffee. If 1:16 tastes weak, try 1:15. If it tastes overpowering, try 1:17.

See also