Now you know the history of espresso machines, here’s a rundown on how they work. Water is heated under pressures of up to 220kpa (the same pressure as in a car tyre!) to a temperature of 90 degrees C. As the water travels through the machine to the filter unit, which contains the ground coffee, it cools by 5-8 degrees, reaching the optimum level for good coffee. Experts agree this machine makes excellent coffee if used correctly