Tamping is a lever. The lever is your hand and the coffee and the puck, and the
fulcrum is the group head. The thing you are trying to do is apply consistent
pressure perpendicular to the surface.
What I was taught
Tamp down. Use 30 pounds of pressure. Tamp level. Tamp with a twist. Tamp
three times if you are fancy.
What actually matters
- Consistency, so the shot tastes the same way twice
- Pressure perpendicular to the puck, so the water flows through evenly
- The pressure is less important than the evenness
The shot that failed because the tamp was 25 pounds instead of 30 is usually
fine. The shot where the tamp was tilted to one side will taste wrong every
time.
The argument about pressure
The people who say pressure does not matter are halfway right. The people who
say it does matter are also halfway right. The thing they are arguing about is
not the pressure, it is the consistency.
A machine that backs off the pressure at the start of the pull—like some modern
machines do—changes the argument. A machine that holds steady pressure
throughout changes it again.
How I tamp
- Grind into the portafilter
- Distribute the grounds with my pinky, knocking the side of the portafilter
to settle them - Tamp straight down, 30 pounds, check the level
- A small twist to break the seal
- Lock and pull
The twist breaks the seal, which some people say is unimportant. The twist is
part of my ritual, and the ritual is part of the consistency, so the twist stays
even if it does not matter.
The tamp that changed everything
Using a level tamp instead of a conical one. The level tamp is wider and
lighter, and it is much harder to tilt. The first shot with the level tamp
tasted better than anything I had made in a month. The reason was that I was
not tilting anymore.
The pressure did not change. The consistency of the pressure changed.
The variable that matters is the one you stop noticing because you have done
it the same way so many times it is automatic.