Glossary · 4 min read
A glossary for the stubborn
Words everyone uses and nobody explains
The forum says “turn up the pre-infusion and try WDT before RDT”. Here is what that means.
- Basket
- The metal basket with small holes, inside the portafilter, that the coffee goes into. Precision baskets have more uniform holes.
- Bottomless (naked) portafilter
- A portafilter with no bottom, so you see the extraction from below. The best teacher for puck preparation.
- Dose
- The amount of dry ground coffee in the basket, in grams.
- Yield
- The amount of espresso in the cup, in grams.
- Ratio
- The yield divided by the dose. 18 g of coffee and 36 g of espresso is 1:2.
- Channelling
- The water finds the easiest path through the puck and rushes through it. The shot is sour and bitter at once.
- WDT
- Weiss Distribution Technique: thin needles break up clumps and spread the coffee evenly before tamping.
- RDT
- Ross Droplet Technique: a few drops of water on the beans before grinding reduce static.
- Puck screen
- A thin metal mesh placed on top of the coffee puck.
- Pre-infusion
- Briefly wetting the coffee at low pressure before full pressure, so the puck soaks evenly.
- Backflush
- Cleaning the group head by sending water under pressure backwards through a blind filter, with a cleaning agent, then rinsing with clean water.
- E61
- The group head Faema introduced in 1961. Today a standard on many Italian home machines.
- PID
- An electronic temperature controller. It holds the water at the set temperature instead of letting it swing.
- Temperature surfing
- Catching the right moment for a shot on machines without a PID, by running water first or by waiting.
- Single dosing
- Grinding exactly one dose of weighed coffee, with no bean hopper on the grinder.
- Retention
- The coffee that stays in the grinder after grinding.
- Dial-in
- Adjusting the grind and the recipe for a new coffee until the shot is good.