The tamp refers to the amount of ground coffee deposit it into the portafilter. It is necessary we might point out and actually critical for the portafilter to remain in the group head at all times. The reason for this is the heat generated from the machine will keep the portafilter at the necessary temperature for proper extraction. If the portafilter is cold critical heat will be lost when the hot water comes in contact with the cold metal resulting an insufficient water temperature to emulsify the oils of the ground coffee. Typically 7 grams of coffee should be dispensed for a single shot and 14 grams for a double shot. Most portafilter baskets will have a fill line indicating the proper amount of coffee needed after compaction. It will be necessary to fill the portafilter with ground coffee higher than the level of the fill line. So it will be at the fill line after being compacted by the tamp.
The compaction of these grounds into the portafilter is known as the tamp. Most espresso machines come with a tool for this purpose. Most grinders also have a protruded piece that will accomplish something similar. We prefer the individual handheld tamp. Often times these tamps have a rounded bottom which can cause an uneven extraction. Look for one that has a flat bottom and is comfortable to hold. Most important a firm, even pressure should be used at coffee should be hard packed with an even down word twisting motion. This will ensure that the pressurized water will be forced evenly through the grounds rather than blasting a hole and allowing the water to find its path of least resistance.
Always be sure to brush excess coffee grounds from the rim of your portafilter with the palm of your hand before inserting it back into the group head. Doing this will ensure a snug fit and help avoid damage to the gasket located in the group head. Each operator in a given coffeebar situation should use the same technique and pressure to ensure the grind will consistently work. Place the portafilter in the appropriate group head and begin your extraction. Remember, if you are extracting a restricted poor or ristretto you should produce three quarters of an ounce of espresso per shot in approximately 18 seconds. If you are extracting a long or lungo one and a half ounces of espresso should be produced per shot in about 25 seconds. If the desired volume of espresso is not produced within a few seconds of these time parameters you will need to dispose of the shot and readjust the grind to produce the proper result. A layer of golden crema on the top of your espresso will be the indicator of your success. After the extraction of your shot is complete dispose of your spent grounds with one or two forceful and level hits to your knock box.
Because coffee is approximately 98% water it almost goes without mention that water quality is essential. In many areas and in-line water filter may be necessary to obtain acceptable water quality.
Let's review what it takes to extract the perfect shot of espresso:
- Start with a quality coffee roasted and blended for espresso
- Be sure your portafilter always remains in the machine to maintain proper temperature
- Constantly monitor your grind and adjust if necessary
- Dispense the proper dose of ground coffee for the desired extraction
- Hard pack the coffee with a firm and consistent tamp
- Place the portafilter back into the group starting the brewcycle taking note of the extraction time and volume produced
- Judge the result of your shot by the crema produced
Description: Typically 7 grams of coffee should be dispensed for a single shot and 14 grams for a double shot. Most portafilter baskets will have a fill line indicating the proper amount of coffee needed after compaction. It will be necessary to fill the portafilter with ground coffee higher than the level of the fill line.
