- Good puck preparation is essential for even extraction in espresso. A good puck doesn’t just have a flat surface; it has an even density and distribution of particle sizes throughout.
- The appearance of the spent puck doesn’t tell us much about how good our puck preparation was, but we can use the refractometer and bottomless portafilters to evaluate distribution and tamping technique.
- Good distribution begins at the grinder. By setting up and using the grinder in such a way that the coffee falls evenly into the basket, we reduce the need for later corrections from the barista.
- Distribution also includes the relative distribution of fine particles, which can be affected by grinder performance. ‘Fines migration’, however, isn’t a concern.
- The most effective distribution methods in a cafe setting are based on tapping to settle grinds into the basket.
- Evidence suggests that using distribution tools to create even density is not as effective as tapping.
- Tamping is of secondary importance to effective distribution in creating a good puck.
- Tamping pressure has little effect on shot time or extraction.
- Tamping — even light tamping — can cause injury to a barista over time. To avoid back and shoulder strain, pay attention to posture and body movements during tamping.
Exhaust The pipework responsible for releasing the pressure in a puck when a shot finishes brewing and for transferring any waste liquid into the drain.
Fines migration The movement of fine particles through a bed of coffee, whether settling to the bottom in dry coffee or being actively carried through the puck by the flow of water.
Naked portafilter Also called ‘bottomless portafilter’ — a portafilter with the spouts and lower surface removed, exposing the bottom of the basket.