What is an espresso?

An espresso is a coffee extracted under pressure — 9 bars of water at 92-94 °C forced for 25 to 30 seconds through 18 to 20 g of finely ground, tamped coffee, yielding roughly 36 to 40 g of concentrated liquid topped by a crema. Invented in Italy in the early 20th century, it is the most standardised coffee drink in the world and the base of most modern milk-based drinks.

Espresso's industrial birth dates to Milan, 1901, with Angelo Moriondo's patent later refined by Luigi Bezzera and marketed by Desiderio Pavoni. But the 9-bar pump machine we know today only became widespread after World War II: Gaggia's spring-lever model in 1948, then Faema's E61 brewhead in 1961, whose thermosyphonic group is still the technical benchmark for most professional machines.

The historical Italian standard, codified by the Istituto Nazionale Espresso Italiano, defines espresso as 25 ± 5 seconds of extraction at 9 ± 1 bar, 88 ± 2 °C at the group exit, 7 ± 0.5 g of ground coffee for a 25 ± 2.5 ml single shot. The third wave rewrote those numbers: specialty baristas now pull 18 to 20 g doses for a double, with a yield of 36 to 40 g — roughly a 1:2 brew ratio. That shift reflects a different philosophy: classic Italian espresso seeks intensity and roundness, third-wave espresso seeks transparency of origin and variety.

The crema — the 2-to-4 mm persistent brown foam — is an emulsion of oils and a burst of CO2 trapped in freshly roasted coffee. It is neither a reliable proxy for quality nor an absolute freshness indicator: a very thick, dark crema usually points to Robusta or a heavy roast, while a thin amber crema is typical of light Arabica roasts. A balanced espresso sits between 8 and 12 % TDS, about ten times more concentrated than a filter brew, which is why a 36 g espresso and a 250 g filter cup can deliver similar caffeine loads.

In Belgium, espresso spread after the war through Italian cafés in Brussels, Charleroi and Liège, before becoming the default drink of 2010s specialty bars in Saint-Gilles, Ixelles, Ghent and Antwerp. Belgium is a top-ten European coffee consumer at about 6.8 kg of green beans per person per year, but espresso still lags behind filter in daily volume — an older generation drinks koffie verkeerd, not ristretto al banco.

Espresso parameters — Italian vs third wave