Extracting espresso is a skill that requires practice, and awareness of the factors will ultimately impact the quality of the shots you pull. The following guidelines, deemed by some to be the "Golden Rules" of espresso extraction will provide you with a solid foundation of knowledge with which to begin your foray into the world of home espresso.
- Single Shot - 1-1.5 fluid ounces of water, pulled through approximately 7 grams of ground coffee in 20-25 seconds.
- Double Shot - 2-2.5 fluid ounces of water, pulled through approximately 14 grams of ground coffee in 20-25 seconds.
Dosing Your Coffee
Based on the type of filter basket you are using (a single or a double shot) the amount of ground coffee used will vary. For a single shot, 7-9 grams of ground coffee should be used. For a double shot, 14-16 grams of ground coffee should be used. Please note that Gaggia, commercial style, filter baskets are traditional double-shot filter baskets that hold between 14-16 grams of ground coffee.
Tamping is the process of applying pressure to your ground coffee to compact it into an even puck. Tamping is an important step in the extraction process, as it impacts the rate of water flows through the grounds. A tamping pressure of approximately 30 lbs is ideal for extracting consistent, quality shots of espresso.
Alongside tamping, the fineness of your grind is an important factor in determining the flow rate of your water through the grinds. Unlike tamping pressure, which can be maintained at a constant 30 lbs, the fineness of your grind will need to be adjusted as your coffee ages. As the coffee gets older and dries out, it will need to be ground more finely in order to extract the same kinds of ideal, crema rich shots. As a rule, the finer the coffee is ground, the slower the flow rate will be.
As indicated above, the total time required to extract a single or double shot of espresso should be approximately 25 seconds. By timing your shots, you can observe whether your shot is flowing too fast or too slow, and adjust the other variables accordingly.