Fix a Sour or Bitter Cup

A taste-to-cause-to-adjustment table: what sour and bitter mean for grind, contact time and ratio.

Extraction yield is the share of the dry coffee that dissolves into the cup; the accepted target range is about 18 to 22 percent. Under-extracted coffee tastes sour and thin, which means the yield sits below 18 percent. Over-extracted coffee tastes bitter and drying, which means the yield sits above 22 percent.

The first adjustment is the grind, because grind size controls the contact surface and moves extraction fastest. Finer grinds extract faster and suit short methods; coarser grinds suit long immersion. If the cup is sour, go finer; if it is bitter and drying, go coarser.

The second adjustment is contact time. A sour cup can come from a drawdown that finished too quickly or a steep that was cut short; a bitter cup can come from a steep that ran long. French press steeps for about 4 minutes before the plunger is pressed down; espresso yields roughly 25 to 35 millilitres in 25 to 30 seconds at about 9 bars.

The third adjustment is the ratio, which changes strength more than it changes extraction. The band is 1:15 to 1:17 coffee to water by mass, about 60 grams of coffee per litre of water. Water temperature also matters: the ideal brewing water temperature is about 90 to 96 degrees Celsius, and much hotter water extracts harsh compounds.

• Sour and thin: extraction under 18 percent — grind finer or extend the contact time.
• Bitter and drying: extraction over 22 percent — grind coarser or shorten the contact time.
• Change the grind first, then the time, then the ratio.
• Keep the water at 90 to 96 degrees Celsius; outside that band the ratio cannot compensate.

Further reading

• Ratios for Every Method
• Pour Over, Step by Step