A shot of espresso is made by forcing about 1.5 ounces of hot water through tightly packed, finely ground espresso coffee. If everything goes well, what comes out is a dark brown, slightly thick liquid with a small amount of crema (a foam, sort of like the head on a beer) on top.
There are many variables in the process of making a shot of espresso. The temperature of the water, the pressure of the water, the fineness of the ground coffee and how tightly the coffee is packed are just a few. The skilled espresso maker, or barista, controls all of these variables to produce a quality shot of espresso. Let's start with one of the most crucial variables: the coffee.
Espresso coffee is a blend of several different types of coffee beans from different countries. The beans are roasted until they are dark and oily-looking.
The beans are ground very finely, much finer than for drip coffee makers. The consistency is almost like powdered sugar. The more finely the coffee is ground, the slower the espresso comes out. Generally, for the best shot of espresso, it should take about 25 seconds for the water to pass through the coffee. Sometimes the grind is adjusted to control the brewing time.
To steam some milk for example, a cafe latte, you place a container with some cold milk under the steam wand so that the wand is submerged. Then, you turn the valve to the steam position. This energizes the resistive heater, which quickly boils the water in the heating vessel and opens the valve, starting the flow of steam out of the nozzle. The pump runs intermittently to keep the heating vessel supplied with water. The steam quickly heats up the milk, and, if you hold the steam nozzle near the surface of the milk, can be used to make froth.
There are dozens of different espresso based drinks that you can make with an espresso shot. With the help of an espresso machine, you can explore your own coffee. This is also a way to find quality time with family and friends like making latte art or making your best espresso shot.