Espresso coffee is produced when water approaching boiling point is forced under pressure through a compacted amount of string coffee grounds.
A good espresso is a rich dark strong brew with distinctive brown foam that floats on its surface – the famous crema. Originally the crema was thought to be undesirable, but now it is thought of as the crucial way to judge the quality of a good espresso. It is the main ingredient and base for most coffee shop drinks including cappuccino and latte.
It is said that the first ever espresso machine was invented in France in 1822 and not Italy as one might expect. In fact espresso machines were around in various forms for over 100 years before the Italian Achille Gaggia applied for the first patent in 1938. Mr Gaggia devised a system using a powered lever system to force hot water through the coffee to produce espresso. The name Gaggia is closely associated with espresso machines even today.
A couple of decades later, in 1960 the Faema Company starting manufacturing machines that used a pump system for producing espresso.
Every espresso machine has at least one brew point, commonly known as a group. Close to these are the group handles which contain the metal filter baskets and compacted coffee. Usually espresso machines for the home only have a single group head. Commercial machines for busy coffee shops typically have 2 or 3 group heads and can contain up to 4. The group handle is fitted with either one or two spouts which direct the espresso into a coffee cup below as it is brewed and forced through. That means an espresso machine can brew up to twice the number of cups as it has group heads simultaneously.
Espresso equipment uses three different types of extraction methods: steam, piston and pump driven. The steam model uses steam to force water into and through the grounds using steam pressure. These were the first type of machines produced and although this technique is not used for commercial equipment it is still used for domestic machines today.
The piston versions use a piston or long lever to pressurise hot water and force it through the coffee. This is where the origin of the phrase, ‘a shot of coffee’ comes from. The act of pulling the lever became known as pulling a shot.
In the pump version, a motor pump provides the work to force the water through the coffee rather than needing force applied by a manual operator. The pump method is commonly used in sturdy commercial coffee equipment suitable for heavy usage.