Smithsonian.com

Photo: Brian Legate

Few can deny the invigorating pleasure of a strong shot of espresso to start the day. But what, exactly, is this bitter blend? Popular Science argues that espresso is a widely misunderstood beverage, and difficult to define.

Surprisingly, there is no real definition of espresso–there are certainly elements that the experts agree on, but there are no codified guidelines, no explicit recipes.

Espresso connoisseurs do agree, however, that espresso is: concentrated, thick, coffee-based, topped with a layer of dense foam and created with a machine that forces hot water through a basket of tightly packed, finely ground coffee at very high pressure.

“Espresso” may also serve as a blanket term for the process that creates this mystery-shrouded beverage.

On the other hand, espresso is not: a type of bean, the same thing as strong coffee, pronounced “expresso” or  likely to ever arrive at a single, unified definition.

One thing the espresso aficionados do agree on, though, is the uncompromising importance of the equipment that produces their caffeinated cafe-staple of choice:

It’s hard to nail down what is and is not espresso when there’s no definition, but everyone I spoke to agreed that pretty much every home espresso maker that costs less than $1,000 is incapable of producing enough pressure, power, and consistency of temperature to produce a shot anywhere near the level of tastiness that a proper commercial machine can make, though some were more disdainful of home machines than others.

But as Smithsonian wrote recently on the Design Decoded blog, there is also a necessary human element behind the mix:

Over more than a century, the espresso machine has been drastically improved, with electrical components, computerized measurements, and portable pneumatics. But as with the finest objects of design, science and technology is not enough. There is an art to the espresso as well. The talent of the barista is as important as the quality of the beans and the efficiency of the machine. Indeed, it is said that a good espresso depends on the four M’s: Macchina, the espresso machine; Macinazione, the proper grinding of a beans –a uniform grind between fine and powdery– which is ideally done moments brewing the drink; Miscela, the coffee blend and the roast, and Mano is the skilled hand of the barista, because even with the finest beans and the most advanced equipment, the shot depends on the touch and style of the barista.

More from Smithsonian.com:

Across the Country, It’s All Happening at the Coffee House 
Coffee Pods, an Instant Classic