Glossary of Espresso and Coffee terminology

Burrs

The part of the grinder that does the grinding. Burrs are either a cone and collar or a pair of flat discs that break down coffee beans in stages resulting in a relatively evenly ground coffee.

Dialing In

The process of narrowing in on the ideal parameters to extract a given coffee. This involves determining the dose and yield (ratio) as well as shot time, PI time, and any profiling. This can sometimes feel like chasing your own tail.

The most important thing to know is that it is best to change a single variable at a time. Espresso is quite complicated and changing multiple variables (especially when you are new to the hobby) can lead to sometimes confusing results.

Dose

The amount of dry coffee beans used for a brew. Usually expressed as a weight in grams.

EY (Extraction Yield)

A way to represent the amount of coffee extracted during brewing/pulling a shot. If you enjoy some light mathematics, you can derive EY by obtaining a TDS measurement and plugging it (and the needed variables) into this formula:

Extraction Yield % = Brewed Coffee (g) x TDS (%) / Dose (g)

Hopper

That big thing on top of your grinder designed to act as storage for unground beans. Box it away unless you’ve found your one perfect, unbeatable forever coffee.

PI (Pre-Infusion)

Saturating a prepared puck with water at very low pressure prior to the full desired brew pressure being applied. General consensus is that pre-infusion promotes a more even extraction. The length of PI varies from machine to machine, with some allowing manual control of differing degrees during this stage of extraction.

If your machine offers any control over Pre-Infusion it is definitely worthwhile experimenting with. It can help round out a coffee extraction.

Another hotly debated topic in this wonderful hobby.

Ratio

Refers to the relationship between the weight of ground coffee used and the weight of the final resultant brew. Usually formatted as: Dose (grams) : Yield (grams)

A 1:2.5 ratio would refer to a shot where there is 2.5x brewed espresso as there was dry coffee

RDT

Ross Droplet Technique. Adding a very small amount of water (usually with a small spray bottle) to your beans before grinding to eliminate some static. Only applicable to single dose grinding.

Retention

Ground coffee that remains inside your grinder and does not exit through the chute. Some of this coffee fills up dead space inside the grinder, never to be seen again. Some, however, just remains in the exit chute until more coffee is ground, exiting with your next grind. If you swap out coffee often, purging a few grams of beans before grinding your dose is a way to prevent old coffee and new mixing.

Shot Time or Brew Time

The time (in seconds) taken to pull your shot. The point at which you start timing the shot is one which is often debated. The important thing is consistency. Shot times can then be used to dial in your grind and fine tune your extractions.

Single Dose Grinding / Single Dosing

Weighing out and grinding exactly the amount of coffee beans needed to pull one shot or produce one batch of brewed coffee.

This is partly to avoid coffee beans going stale in the hopper in a home environment. The more compelling reason to single dose is that you can rotate different coffees rather than drinking 200g of a roast (or whatever will fit in your hopper) before being able to try something else or drink some decaf.

WDT

Weiss Distribution Technique. Using fine prongs to more evenly distribute the ground coffee in your basket, while also breaking down any clumps caused by static or other dastardly forces. Some recommended tools to use for WDT:

Unfurled paper clip, blunted sewing needle, acupuncture needles

All of these can be fitted into handles of various types such as bits of cork, erasers, pieces of wood or metal or 3d printed contraptions.

Yield

The wet weight of the extracted coffee.