We define ‘Espresso’ as: ‘pressurized water at 9-10 bars of pressure, at 85-95 degrees Celsius, pushed through finely ground coffee, extracting aromatic oils, sugars and other solubles, yielding approximately 30ml of beverage, with a thick crema, balanced flavor and a lingering after taste'.
Aiming at brewing espresso, we need to ensure water temperature and pressure in the machine are being delivered consistently to the brewing group.
Single Boiler (Duel Purpose) machines incorporate a boiler as its water heating device. As oppose to a thermoblock, widely available in many domestic machines, a boiler allows an internal water circulation that delivers a more stable water temperature for espresso brewing as well as a buildup of a high steam pressure than the one available with a themorblock. High steam pressure is essential to achieve 'microfoam': silky, creamy, bubble and froth free milk texture, which we like so much for our lattes. Single boiler machines require wait time for water temperature to rise to steam from brewing, and to drop from steaming back to brewing. Time may vary between 30 second to 1.5 minutes based on size of boiler, brewing mechanism and the heat cycle.
Single boiler machine are mostly suited for the coffee connoisseurs who upgrade from a non espresso coffee maker or from a thermoblock machine, It is also suitable as a first machine buy for the novice who appreciate their coffee and want to replicate their favorite barista coffee quality at home. These machines will not be suitable for the heavy entertainer who would like to easily make 6-8 milky coffee consecutively. Since the machine operation requires heating up and cooling down in temperature, high volume coffee would result in a long time of wait and potentially in compromising with the coffee quality as we tend to ‘cut corner’ just so we complete all coffee orders in time. If you are an entertainer, click on our Heat Exchange or Double Boiler machines category to learn more. Di Bartoli offers the following single boiler machines: Rancilio Silvia, the Isomac Venus, the Vibiemme Domobar Piccolo (e61 brewing head) and the Isomac Zaffiro (e61 brewing head).