Boiler
A boiler is a device used to generate and maintain high temperatures of water or steam. In the context of coffee brewing, the boiler is commonly used in Espresso machines.
Typically, this device is made of thermally conductive metals, with the most common being aluminum, brass, copper, and stainless steel. Aluminum and brass are often used in cheaper Espresso machines, while copper and stainless steel are found in more expensive commercial machines.
There are two main types of boilers: single boiler (one boiler for both Espresso brewing and milk steaming, requiring a mode switch) and multi-boiler (two or more separate boilers, allowing Espresso brewing and milk steaming to occur simultaneously). Both types ensure stable temperatures for high-quality Espresso, and each type has its own advantages and disadvantages, catering to different needs and usage purposes.