Evolution of the Caffe Machine. The first European patents for steam-pressure coffees machines were filed between 1821 and 1824. A variation of the method was first applied to a large caffe machine by Edward Loysel de Santais in 1843. Santais’s machine wowed visitors to the Paris Exposition of 1855 by producing "two thousand cups of coffee an hour." Santais’s machine brewed coffee a pot at a time, however, and used steam pressure, not to force the brewing water directly through the coffee, but, instead, to raise the water to a considerable height above the coffee, from whence it descended through an elaborate system of tubes to the coffee bed. The weight of the hot water, not the trapped steam, applied the brewing pressure.
New Century, First Espresso Machine. It was not until the dawn of the 20th century that the Milanese Luigi Bezzera patented a restaurant machine that used the pressure of trapped steam to directly force water through ground coffee. The Bezzera machine also innovated by distributing the freshly brewed coffee through one or more "water and steam groups" directly into the cup.
In many respects the Bezzara machine established the basic configuration that espresso machines would maintain throughout the 20th century. These machines decreased the size of the strainer that held the coffee, but increased the number of valves, enabling them to produce several single cups of coffee simultaneously, rather than a single big pot at a time. Then as now, the espresso operator packed a few teaspoons of very finely ground, dark-roast coffee into a little metal filter. The filter was clamped into a receptacle called the group, which protruded from the side of the machine. When the operator opened the valve (or, in more modern machines, pulls a handle or pushes a button), hot water was forced through the coffee and into the cup.
The Gaggia Breakthrough. In 1948 Achille Gaggia introduced the first truly modern espresso machine. As Gaggia’s design eventually evolved, the water tank was laid on its side and concealed inside a streamlined metal cabinet with lines like a Danish-modern jukebox. The simple valve of the old days was replaced with a spring-powered piston that pushed the water through the coffee harder and faster. The operator depressed a long metal handle. The handle in turn compressed a spring-loaded piston that forced a dose of hot water slowly through the coffee as the handle majestically returned to its original erect position. The new spring-loaded machines pushed the water through the coffee at a pressure that is now accepted as ideal for espresso brewing: a minimum of nine atmospheres, or nine times the ordinary pressure exerted by the earth’s atmosphere. By comparison, the pre-war steam-pressure machines exerted a feeble one-and-a-half atmospheres of pressure.
Computer-Age Espresso. In the 1960s, just when pumping the handle became the signature performance piece of espresso caffes, less dramatic and more automated means for forcing the hot water through the coffee began to evolve. The earliest of these no-hands machines were built around simple hydraulic pumps. Today’s versions heat water separately from the main reservoir, control water temperature and pressure with precision, and flatter the hi-tech pretensions of the late 20th century with digital read-outs.
These push-button machines tend to carry the streamlined look to an extreme. Everything is concealed inside a single, sleek enamel and chrome housing. All have one feature in common: The operator pushes a button or trips a switch rather than pumping a long handle. Since so much of the process is automated, the push-button machines are easier for the novice to master, but do not necessarily make better espresso. Proprietors of some of the better caffes in the San Francisco Bay Area, at any rate, still prefer the pump-piston machines because they give the sophisticated operator maximum control over the brewing process.
Enter Frothed Milk. With the long, gleaming handle going the way of the running board, the best routine left to the espresso operator is heating and frothing the milk used in drinks like cappuccino and caffè latte. Espresso is a strong, concentrated coffee, and, in accordance with European tradition, many of the drinks in espresso cuisine combine it with milk. If the milk were unheated, it would instantly cool the coffee. Early in the history of the espresso machine, someone, probably Luigi Bezzara in 1901, realized that the steam collected in the top of the tank could be used to heat milk as well as provide pressure for making coffee. A valve with a long nozzle was fed into the upper part of the tank where the steam gathers. When the valve is opened by unscrewing a knob, the compressed steam hisses out of the nozzle. The operator pours cold milk into a pitcher, inserts the nozzle into the milk, and opens the valve. The compressed steam shoots through the milk, heating it and raising an attractive head of froth or foam.