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

A: 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 times, 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.

John R said:

I don't like the idea of repeatedly drinking water that has been heated in a brass/copper boiler precisely because of the copper that might leach into the water. Yes it kills bacteria but it may not be exactly great for humans either. I'd prefer stainless steel.

John R said:

On looking into what brass can be made of, I find lots of different types of brass, with lead and other metals present in small percentages: Brass types Admiralty brass contains 30% zinc, and 1% tin which inhibits dezincification in many environments. Aich's alloy typically contains 60.66% copper, 36.58% zinc, 1.02% tin, and 1.74% iron. Designed for use in marine service owing to its corrosion resistance, hardness and toughness. A characteristic application is to the protection of ships' bottoms, but more modern methods of cathodic protection have rendered its use less common. Its appearance resembles that of gold.[26] Alpha brasses with less than 35% zinc, are malleable, can be worked cold, and are used in pressing, forging, or similar applications. They contain only one phase, with face-centered cubic crystal structure. Prince's metal or Prince Rupert's metal is a type of alpha brass containing 75% copper and 25% zinc. Due to its beautiful yellow color, it is used as an imitation of gold.[27] The alloy was named after Prince Rupert of the Rhine. Alpha-beta brass (Muntz metal), also called duplex brass, is 35�45% zinc and is suited for hot working. It contains both ? and ?' phase; the ?'-phase is body-centered cubic and is harder and stronger than ?. Alpha-beta brasses are usually worked hot. Aluminium brass contains aluminium, which improves its corrosion resistance. It is used for seawater service[28] and also in Euro coins (Nordic gold). Arsenical brass contains an addition of arsenic and frequently aluminium and is used for boiler fireboxes. Beta brasses, with 45�50% zinc content, can only be worked hot, and are harder, stronger, and suitable for casting. Cartridge brass is a 30% zinc brass with good cold working properties. Used for ammunition cases. Common brass, or rivet brass, is a 37% zinc brass, cheap and standard for cold working. DZR brass is dezincification resistant brass with a small percentage of arsenic. Gilding metal is the softest type of brass commonly available. An alloy of 95% copper and 5% zinc, gilding metal is typically used for ammunition "jackets", e.g. full metal jacket bullets. High brass contains 65% copper and 35% zinc, has a high tensile strength and is used for springs, screws, and rivets. Leaded brass is an alpha-beta brass with an addition of lead. It has excellent machinability. Lead-free brass as defined by California Assembly Bill AB 1953 contains "not more than 0.25 percent lead content".[12] Low brass is a copper-zinc alloy containing 20% zinc with a light golden color and excellent ductility; it is used for flexible metal hoses and metal bellows. Manganese brass is a brass most notably used in making golden dollar coins in the United States. It contains roughly 70% copper, 29% zinc, and 1.3% manganese.[29] Muntz metal is about 60% copper, 40% zinc and a trace of iron, used as a lining on boats. Nickel brass is composed of 70% copper, 24.5% zinc and 5.5% nickel used to make pound coins in the pound sterling currency. Naval brass, similar to admiralty brass, is 40% zinc and 1% tin. Nordic gold, used in 10, 20 and 50 cts euro coins, contains 89% copper, 5% aluminium, 5% zinc, and 1% tin. Red brass is both an American term for the copper-zinc-tin alloy known as gunmetal, and an alloy which is considered both a brass and a bronze. It typically contains 85% copper, 5% tin, 5% lead, and 5% zinc.[30][31] Red brass is also an alternative name for copper alloy C23000, which is composed of 14�16% zinc, 0.05% iron and lead, and the remainder copper.[32] It may also refer to ounce metal, another copper-zinc-tin alloy. Rich low brass (Tombac) is 15% zinc. It is often used in jewelry applications. Tonval brass (also called CW617N or CZ122 or OT58) is a copper-lead-zinc alloy. It is not recommended for seawater use, being susceptible to dezincification.[33] White brass contains more than 50% zinc and is too brittle for general use. The term may also refer to certain types of nickel silver alloys as well as Cu-Zn-Sn alloys with high proportions (typically 40%+) of tin and/or zinc, as well as predominantly zinc casting alloys with copper additive. Yellow brass is an American term for 33% zinc brass.