WDT (Weiss Distribution Technique)
also: Weiss Distribution Technique, needle distribution
Stirring dry espresso grounds with thin needles to break clumps for even extraction.
WDT, the Weiss Distribution Technique, is stirring the dry grounds in your espresso basket with a set of thin needles before tamping. Named after John Weiss, it breaks up the clumps that grinders produce and spreads the coffee evenly across the basket.
Why it matters: ground espresso comes out of the grinder in clumps and uneven mounds. If you tamp that as-is, you bake in dense and loose spots. Under pressure, water shoots through the loose areas, a defect called channeling, leaving the rest under-worked. The shot tastes simultaneously sour and bitter and pours unevenly. Gently raking through the grounds with fine needles (often around 0.3 to 0.5 mm) declumps and levels the bed so the puck presents uniform resistance.
WDT is one of the highest-impact, lowest-cost upgrades to shot consistency, which is why it is central to modern puck prep. Keep the stir gentle and reach the bottom corners without compacting the center. It pairs well with RDT: RDT keeps static and clumping down coming out of the grinder, WDT finishes the job in the basket.