We all know that bartenders "pull" a beer from the tap into your glass, and that the word barista means "bartender" in Italian, but have you ever wondered where the term "to pull a shot of espresso" come from?
Get out your coffee-vocabulary sheets, friends: It's time for a jargon lesson.
In the early days of espresso—say, from about 1901 until 1935 or so—the machines baristas used to coax strong brown syrup from beans were pretty primitive, relying solely on built-up steam pressure within an enclosed tank to force hot water through a puck of espresso grounds.
Because he was relying on the strength of that steam, the barista had little control over the force with which the water was pushing through, having to wait until the pressure built by constantly heating water to an incredibly high temperature within the machine's main boiler tank.
Starting in the late 1930s and early 1940s, a wave of espresso machine innovations were taking place throughout Italy, inspired by visionary experiments relating to taste and temperature conducted by folks like boilermaker Achille Gaggia. (If the name "Gaggia" sounds familiar, it's because it also belongs to his still-extant espresso-machine manufacturing company.)
In 1938, Gaggia took out a patent for the first espresso machine not powered by steam pressure alone. Instead, his design utilized a spring-loaded lever apparatus, by which a barista could not only control the pressure of the espresso extraction, but also ramp it up pretty significantly, to as much as about 14 bars of pressure from the relatively tame 1.5 bars created by the steam-based system.
The barista pulled down on the machine's lever, which allowed water to build up in a small reservoir just above where the ground coffee sat in a portafilter. When he released the lever, a tightly coiled, contracted spring would slowly start to expand inside the reservoir, pushing against the water as it opened and returning the lever to its upright, at-rest position. The force of the spring against the water caused it to flow through the tightly compacted ground coffee, creating the espresso liquid.
Hence, the barista had "pulled a shot."
By increasing the pressure used to brew, and by simultaneously dropping the temperature of the brew water by up to 20°F by not using the hot steam to extract the coffee, the magic elixir oozing out of Gaggia's machines were thicker, richer, and sweeter. Not only that, but they also had a delicious head of aromatic foam on top, which no one had ever seen before: crema.
That creamy stuff caused such a craze in Gaggia's home base of Milan that throughout Italy people were demanding "caffe crema" instead of their usual "caffe espresso" from their regular bartender. Everybody suddenly needed a Gaggia-style lever machine!
These days, of course, the average barista pushes a button on the face of an espresso machine, engaging an electric motorized pump and calling water through at a pressure dictated by a computer board inside the machine's brain.
"Pushing a shot" just doesn't have quite the same ring to it for some reason.