Espresso Machine Boiler Material Pros and Cons

29th Mar 2018

  • Aluminum – Aluminum heats up fast and transfers heat fast. This material is usually used for machines that have thermoblocks as it can quickly transfer heat to water as it’s flowing through. The drawback to this material is that it has poor temperature stability, which creates fluctuation of temperature during extraction and makes it difficult to maintain accurate brewing or steaming temperature. Aluminum is usually found in lower priced espresso machines and in super automatics that have thermoblocks.
  • Brass – Brass has better temperature stability that aluminum and transfers heat fairly fast. It has better temperature stability and consistency than aluminum, but there is still temperature fluctuation. It’s usually used on lower priced prosumer machines that have true boilers.
  • Copper – Copper is an outstanding boiler material in terms of temperature consistency and stability, especially when used in combination with boiler insulation. It is used on many mid-range to high-end espresso machines. Copper can leach into water over time and there are people that have health concerns about this, but most, if not all new espresso machines have some kind of plating (such as nickel plating) on the inside to prevent leaching. Another drawback of copper is that it is more susceptible to limescale buildup when compared to stainless steel.
  • Copper with Brass – A few machines, such as the Rocket brand machines have copper boilers with brass end plates. The idea behind this is more rapid heat transfer from the brass, but also temperature stability from the copper. Rocket machines that have this boiler design as said to have about 40% better performance when compared to similar machines with copper only.
  • Stainless Steel – Stainless steel is found on both lower quality and very high-quality machines. Lower end machines have thin stainless-steel boilers that have poor temperature consistency and stability. High end machines have thick stainless-steel boilers that have great temperature stability and consistency, especially when insulated. Stainless steel doesn’t have the leaching issue that copper does and is the least susceptible material to limescale build up.