The espresso machine has been around since 1884 and was built by Angelo Moriondo of Turin, Italy. His design was patented and has been improved several times since then. There is a myriad of machine options available but most have the same basic parts. These machines can be driven by steam, pumps, air pumps, or pistons and come in a manual or an automatic version. Much like a car, there is more flexibility with a manual setup than an automatic, but coffee shops are using automatic machines more and more.
Semi-automatic espresso machines use a pump to push the water through a three-way valve. Automatic machines are pre-programmed to use a specific amount of water and run through a meter than controls the shutoff. The Super-automatic machine works exactly how it sounds, automating every step of the brewing process for the barista. Some of these machines even have an automated milk frothing system which is great for beginner baristas but limiting for the seasoned professional. Any of these machine types can be “plumbed” to a water supply or have a reservoir that can be filled as needed.
After the ground coffee is tamped into the portafilter and it is attached to the group-head, the barista turns the machine on to brew. Compressed air is used to force hot water through the grounds and over into the receiving cup to create the espresso shot. Generally speaking, most machines will provide up to a quad shot (that is 4 ounces) with one full tamp of grounds. However, each machine and barista is different and this can vary from establishment to establishment.