Technique · espresso
WDT, the Weiss Distribution Technique, stirs espresso grounds with fine needles before tamping to break up clumps and stop channeling. Method and tool.
WDT — the Weiss Distribution Technique — means stirring the dry grounds in the basket with a set of very fine needles before tamping.
Grinders produce clumps. Static and oil bind fines together, and a clump is denser than the surrounding bed. Water takes the path of least resistance, avoids the clump, and rushes through a channel instead.
Channeling is the single commonest cause of a shot that runs fast, tastes sour and bitter at once, and is not repeatable.
Tamping does not fix it. Tamping compresses a clumped bed into a compressed clumped bed.
Needles of 0.3 to 0.4 mm (0.01 to 0.02 in). Thicker ones push grounds around instead of passing between them, and are much less effective.
Acupuncture needles in a cork is the original improvised version and works exactly as well as a machined one.
More consistent shot times at the same grind setting, often slightly slower — because the bed is now uniformly dense instead of full of shortcuts.
Re-dial after adopting it. Your old grind setting will likely be too fine.
The equipment this actually requires — not a shopping list, the shortest route to doing it properly.
8 × 0.4 mm (0.016 in) needles · magnetic stand
Eight fine needles you stir through the grounds before tamping. It costs about $25 and fixes more bad shots than any other accessory here — including ones costing twenty times as much.
Best for: Every single person with a non-pressurized basket. There is no exception worth naming.
58 mm (2.28 in) commercial portafilter · 3-way solenoid · steel body
A 58 mm (2.28 in) commercial portafilter, a steel body and a three-way solenoid, in a machine cheap enough to modify. Nothing else at this price is still worth owning in fifteen years, and nothing else has this much of an aftermarket.
Best for: Someone who wants one espresso machine for the next fifteen years and does not mind learning it.
