Espresso is a beverage made from just two ingredients: water and ground coffee beans. From this ingredients-based perspective, espresso appears to be a rather simple and straightforward drink. In fact, if you look at it from this limited viewpoint, it's no different than coffee from a fast food drive thru.
The brewing process (and often the blend of coffee beans) is what distinguishes espresso from coffee. In fact, in espresso making, the brewing process is so critical that adherence to the process is also what consistently separates bitter espresso from better espresso. Since the process is so critical, let’s examine it further.
Espresso Brewing Process
Take clean water, between 195-205 degrees Fahrenheit, and, at 9 BAR of pressure, force it through fresh, finely ground coffee that has been tamped at 30lbs. of pressure. Then pull:
a 1 oz. single shot of espresso, made with 7 grams of coffee in 23-25 seconds, OR
a 2 oz. double shot of espresso, made with 14 grams of coffee in 23-25 seconds
First, note that clean water is mentioned. Not only does filtered or softened water make a better tasting cup of espresso, it’s easier on your machine than tap water. Tap water is notorious for leaving hard to clean deposits.
Next, notice that espresso is brewed using water that is heated to temperatures exceeding 190°. The water temperature contributes largely to the extraction and the quality of the crema. However, by the time the heated water travels through the brew group, into your portafilter, through the puck and into your cup, the temperature drops substantially. This is why it's important to have a pre-heated brew group, portafilter and cup.
To properly brew espresso, the hot water must be forced though the coffee grounds at 9 BAR of pressure.
The pressurized hot water must evenly permeate the coffee grounds. This is one reason why a tamp pressure of 30 lbs. is recommended. For a closer look at tamping, see Tamping Basics.
Finally, pull a single (1 oz) shot of espresso, using 7 grams of ground coffee. For a double shot, use 14 grams. The extraction time for both should be between 23-25 seconds.
If all of these guidelines are followed, and your coffee beans are freshly roasted and freshly ground, you should be enjoying an excellent shot of crema-capped espresso. From here you can enjoy the flavor changes caused by different roasts and different coffee beans.
Troubleshooting
The beauty of consistently following each of the steps outlined above is that you have eliminated most of the variables. In other words, if you find that the extraction time is off, you have only one thing to adjust and that’s the fineness or coarseness of the coffee grind.
If you are consistently tamping at 30 lbs. and you are experiencing a shorter than 23-25 second extraction, decrease the size of your coffee grounds. Make the grounds finer. If your extraction time is longer than 23-25 seconds, increase the size of your coffee grounds. Make the ground more course. The coffee grinder is a crucial tool for “dialing in” that perfect shot. In fact, different coffees will require different grind adjustments. On a humid day, the ground size may need adjusted for the same coffee.
If you are purchasing your coffee pre-ground, you are a bit more limited when it comes to dialing in a shot. In this case, try adjusting the tamping pressure. Tamp a bit harder if you are extracting more than 1 oz. in 23-25 seconds. Tamp lighter if you are extracting less than 1 oz. in 23-25 seconds.
If you are using a super automatic espresso machine, you will not have the ability to adjust the brew time or the tamping pressure. The ability to adjust the dose, grind size and water volume will be your tools for dialing in your best shot. As with any espresso machine though, the quality of the water and the coffee bean remain paramount.
