Puck prep is the sequence between the grinder and the machine: dosing, distributing, levelling and tamping.
Its purpose is a bed of uniform density, because water at nine bars finds any part that is less dense and goes there.
The steps, in order of how much they matter
1. Break up clumps. Ground coffee leaves the grinder in knots, and a knot is a dense spot. Stir the bed with a WDT tool — fine needles, through the full depth, ten seconds. This is the single highest-return step.
2. Level the bed. However you do it, the surface should be flat before tamping. A distributor helps; tapping the basket on the bench works too.
3. Tamp level. Pressure barely matters above about 15 kg. Level matters a lot.
4. Do not knock the basket afterwards. Tapping to settle cracks the puck, and a crack is a channel.
What it is not
It is not tamping harder, and it is not buying a heavier tamper.
How to tell if yours is working
A bottomless portafilter. Good prep gives an even column; poor prep sprays sideways. You can change one step and see the result on the next shot.
The order to buy
WDT tool first, at twenty euros. Everything else after.
Last reviewed 8 August 2026