How do you adjust grind to correct extraction?

If the coffee is under-extracted (sour, salty, hollow), tighten the grind by one step. If it is over-extracted (bitter, astringent, ashy), open it by one step. One step typically moves EY by 1-2 points. Change one variable at a time, keeping dose, ratio, temperature and water constant to isolate the effect.

Grind is the most sensitive extraction lever because it acts directly on the water-coffee contact surface. Halving a particle quadruples its surface area, as the classic surface/volume ratio predicts. That is why a tiny shift on a specialty grinder — one 25-50 µm step on a Niche Zero, a DF64 or a Eureka Mignon Specialita — moves TDS by hundredths and EY by 1-2 points.

The disciplined approach, taught by Scott Rao and Matt Perger, is to change only one variable per iteration. Reference recipe: 18 g in, 36 g out, 28 s, 93 °C, SCA water. Taste, measure TDS, calculate EY, then plot the point on the coffee compass (Perger 2015). If the point sits left of the 20 % EY target (under-extracted), tighten one step and try again without touching anything else. If the point sits above the TDS line (too concentrated), extend the ratio instead of the grind.

The logic differs between espresso and filter. In espresso, tightening also lengthens shot time (more hydraulic resistance): one step down typically takes a 25 s pour to 30 s at the same dose and ratio. In filter, tightening slows the drawdown (total water passage time) and raises EY without changing final volume: a V60 that ran in 3:00 climbs to 3:30. On stepped grinders like the Baratza Encore, steps are wide (roughly 100-200 µm); you often prefer to adjust time, ratio or temperature before touching grind.

Jonathan Gagné notes in 'The Physics of Filter Coffee' that a well-aligned flat-burr grinder yields a tighter, more predictable particle-size distribution than a domestic conical burr: the grind/EY relationship is almost linear, which is why DF64, Lagom, Option-O Lagom Mini or Ditting KR804 dominate the specialty scene. On a blade grinder (Bodum, KitchenAid) this regulation is not possible: distribution is too wide, fines and boulders coexist, and no step gives a repeatable result.

Isolated grind adjustment protocol