What is the difference between steam-driven and pump-driven machines ?
To extract a full-bodied espresso, approximately 9 ATMs are required to force the water through the finely ground and densely packed espresso. The steam machine produces approximately 3 ATMs of pressure, compared to a pump-driven machine, which creates anywhere between 9 and 17 ATMs. Furthermore, the temperature of steam-driven machines is often too hot for espresso brewing, which may scald the coffee and create a bitter-tasting drink.
