Achieving perfect espresso is easy if you have the right equipment, good quality coffee, and a little patience. There are a number of key criteria for achieving perfect espresso extraction. Assuming you have a good quality Italian espresso machine and good quality coffee beans, then following the espresso extraction criteria should get you pretty close to perfection in your espresso craft. The following outlines how to go about making espresso in order to follow the espresso extraction criteria, with some tips and good habit thrown in to help improve the overall experience:
Heat your cups
Coffee is sensitive to changes in temperature. So take a moment and heat your cups. If your espresso machine has a hot water wand use this or draw some water throught the brewing group to fill your cups. Set the cups aside to allow them to soak up the heat from the water.
Clean and prepare the portafilter (handle)
Remove the portafilter from the espresso machine. It should be nice and hot. Wipe with a clean dry cloth to remove any coffee grounds and remove any water from the filter basket. You want the filter basket to be clean and dry.
Grind just enough coffee for what you will need
It is important to use freshly ground coffee. Grind just enough coffee for the coffee you are making right now. In a high volume cafe situation you can allow ground coffee to accumulate in the grinder dosing chamber for less than an hour, but this should be discarded after an hour. For home or office use, grind just enough coffee beans then switch off the grinder. Any excess coffee can be collected for use in press-pot (plunger) coffee.
Dose your coffee into the portafilter
Dose the correct amount of coffee infor your portafiler, you are aimin for 7-9 grams of coffee for a single espresso or 14-18 grams of coffee for a double espresso. If you are using a grind-on-demand grinder, coffee is ground directly into the portafilter, otherwise you will operate the dosing lever on a dosing grinder to fill the portafilter.
Settle and distribute your coffee in the portafilter
You may need to tap the portafilter once or twice on the bench to settle the coffee into the portafilter. With the desired amount/weight of coffee the portafilter should be fill to be brim with a flat surface. With a correct setup, you should NOT need to scrape excess coffee off the top of the portafilter. If there is too much coffee in the portafilter scrape the excess off (this cam be used for press-pot coffee).
Tamp (compress) the coffee
Tamping the coffee is very important. The coffee must be tamped evenly to ensure an even extraction across the coffee puck. Just as important is to ensure that the coffee is sufficiently compressed to provide sufficient resistance to the flow of water allowing the right pressure for espresso extraction.
You will want to use a tamper that is the correct size for the portafilter; it is better to use a cheap plastic tamper that correctly fits your portafilter than a fancy tamper that is too small. Press down firmly with approximately 15-20kg of pressure ensuring that the tamper is level with the portafilter. The compressed coffee is commonly referred to as a "puck"; a correctly prepared puck should stay in the portafilter when held upside down.
TIP: After tamping, wipe any excess coffee grounds from the rim of the portafilter and portafilter lugs. It is also usefult to wipe the portafilter spout(s) to remove any stray coffee grinds and prevent these ending up in your drink.
Purge the brewing group
Purging the brewing system allows the temperature to regulate to the optimum conditions for brewing espresso. Engage the pump and wait for a few seconds for water to flow from the group head. Initially steam or very hot water may "hiss" from the brewing group indicating that it is too hot, operate the pump for a few seconds until a steady "shower" of water flows from the group, the disengage the pump.
Insert the portafilter
Now you can engage the portafilter into the group head. The portafilter should engage firmly, but should not be a struggle to tighten. If water flows from around the portafilter when brewing espresso, do not overtighten the portafilter. Water leaking from around the portafilter indicates a worn group head filter seal, this should be changed.
Position your cup(s)
Almost immediately after engaging the portafilter you should discard the hot water from your cup(s) and place them under the portafilter spout(s). Remember that if you are using a double portafilter with just one cup that the cup needs to be positioned below both portafilter spouts. You should aim for not more than 5 seconds between engaging the portafilter and having the cups in position to minimise the time your coffee is sitting "idle" in the brewing group.
Start the brewing cycle
Engage the brewing cycle by activating the coffee delivery function. If you are using a timer, then this is the time to start it. The whole extraction should take 25-30 seconds and should result in 25-30ml for a single espresso or 50-60ml for a double espresso depending on the size of basket you are using. Using a portafilter with two spouts, espresso should extract with two consistent streams that resemble the diameter and appearance of a "mouse tail".
After the desired extraction period, disengage the brewing cycle, or if you are lucky enough to have a volumetric machine your will have pre-programmed this.
TIP: Extraction that gushes or bubbles indicates a flow that is too fast, dripping indicates a flow that is too slow; recalibration of your grind is required.
Empty and clean the portafilter
One of the critical factors to making great tasting espresso is a clean machine. Removing the spent coffee from the machine as soon as possible will help to minimise the accumulation of coffee oils in the brewing group keeping it cleaner, for longer. Remove the portafilter from the grouphead and knock the coffee puck out into a coffee knock box. If you don't have a coffee knock box, get one. Engage the brewing system and rinse the head of the portafilter under the shower of hot water. This helps clean the portafilter aswell as flushing coffee grounds from around the shower screen and grouphead seal. Disengage the pump and wipe the portafilter with a clean cloth. Insert the portafilter back into the brewing group to keep it hot.