Espresso and the Women's Petition Against Coffee (1674)

Coffee brewing has come a long way since the cave-man method of sticking raw coffee cherries in hot water and turning on the heat, to the "sock" filter of the 1780s, to 20th century espresso and the rest of the methods in use by world cultures today.

Espresso is only a centenarian - the first machine was patented in 1901 by Luigi Bezzera, in Milan. Bezzera noticed that his employees were taking too much time with their coffee breaks. [Side note - Apparently this was not a new issue - in 1674 English women tried to outlaw coffee drinking entirely because their men were spending too much time in the coffee houses. Note that these were not pubs - they were places with strict social ettiquette, where men of all social classes would come together to discuss and debate current events and politics.]

The Steam System

In any event, after tinkering in his factory looking for a solution, Bezzera realized that coffee would brew much faster if trapped steam was forced through the coffee grinds. The final product was stronger and thicker, although its taste was bitter, almost burnt. Bezzera's machine was basically a giant Moka pot. Water was heated to produce steam, and because it was under pressure, the steam had no where else to go but through the coffee, quickly extracting the grinds.

The burnt taste issue was really only fixed 50 years later, when heating the water was dissociated from the actual extraction. Espresso had now graduated from the steam system to the piston system. The piston system allowed the barista to pull a lever (hence "pull a shot"), producing pressure which would force the heated water through the grinds. The water was heated completely seperately, in a boiler. No hot steam ruining the taste. Some piston systems work by the lever directly moving the water (direct lever), and some work by having the lever compress a spring, which then applies constant high pressure to produce a consistent extraction (spring lever), such as this shiny one:

Interesting fact: you can tell a spring-lever machine from a direct-lever machine by looking at the resting position of the lever. Up = spring-lever. You pull the lever down ("cock it"), then let the calibrated spring do its job.

This site has a great time-line of the development of different brewing techniques, and this one discusses the difference between the two lever machine types.