WHAT IS A LEVER ESPRESSO MACHINE?
A lever machine is different from the espresso machines we normally see in coffee shops, in that they use a spring to achieve the required pressure while “standard” machines use pumps. As a result, lever machines lack any push buttons or paddles to produce shots because there is no pump to turn on. Instead, one has to pull a lever with force (about 10kg) to load the spring to start the process of genuinely pulling espresso.
The various attributes of a spring lever machine result in a slightly different cup to most pump machines, often producing a fuller body, more velvety mouthfeel, and an easier drinking cup, either with single-origin beans or blends. Even with little experience, it wasn’t that difficult to repeat decent cups.
First, the barista has full control of the length of the pre-infusion stage (pulling the lever down into cocking position): water enters the brew chamber through four holes and the pressure is at boiler pressure/line pressure. This is different to most pump machines where pre-infusion is preset (except in Synesso, Strada, Slayer). It is believed pre-infusion enables one to reduce the chances of channeling so it is much favored.
Second, on releasing the piston, the pressure reaches a high static pressure of 12bar, or higher in some machines. This forces an even column of water through the coffee bed, whereas in a pump machine, water exits from a couple of small holes at the dispersion plate.
Third, as the piston is pushing down, the pressure naturally decreases to zero very smoothly due to the physicality of the spring. The barista can increase or reduce the pressure by manipulating the lever, which is exactly what some advanced machines try to imitate electronically through the pump. These machines, generally double the cost, and one also has to deal with electronic components.