Why brass or copper boilers in the coffee espresso machines are considered to be the “best choice”?

Question

Why brass or copper boilers in the coffee espresso machines are considered to be the “best choice”?

Answer 1

brass and copper heat up faster than steel

Answer 2

1. Heat efficiency. Due to its EXTRAORDINARY THERMAL CONDUCTIVITY and THERMAL CAPACITY brass gets hot much faster and keeps heat much longer than aluminum and stainless steel

2. Anti-corrosion resistance. Even though brass getting the thin film of the oxidized layer on the outside surface it doesn't get corroded inside.  Aluminum oxidizes very fast, corrodes internally and doesn't keep the right temperature that the espresso extraction requires.

3. Health benefits. Copper is considered to be one of the most effective antibacterial metals. In ancient time people used surgical instruments produced from the copper because of its bactericidal properties. The scientific research shows that some life treating bacteria like E.coli survives on the copper surface only for the few hours when it takes 34 days to die on stainless steel. In Italy it is prohibited to use aluminum in the food processed industry.

You can find aluminum and stainless steel boilers on cheap espresso machines produced mostly in Asian countries where the health regulations are not strict. All commercial machines are equipped with brass or copper boilers. There are some espresso machines for home use like Lelit, Brugnetti, Daltio, Expobar, La Scala, Rancilio, Isomac, LaPavoni  that have brass boiler inherited from their commercial cousins.