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Glossary of Coffee Terminology: Espresso Machines

Espresso Machines 

Coffee Glossary Table of Contents

When it comes to the lexicon of espresso machines, it can be overwhelming. Below are some of the most important espresso machine terms to provide assistance when comparing machines.

  • Brew Boiler(s) Capacity: Capacity in liters of the boiler that is directly connected to the brew groups.  A higher capacity brew boiler typically means a higher capacity espresso machine.
  • Boiler Types: The water in any espresso machine is used for 2 functions: extraction in the head (brewing the espresso) and steaming with the wand. 
    • Dual Boiler: The water for brewing and the water for steaming each have their own separate boiler where they get pumped water from the machine's water source. This is a great boiler type because brew and steam temperature can be independently adjusted and set which means more consistency, great for commercial use. But, since they are separate it is a more complex system and requires more extensive repairs and is more expensive. 
    • Heat Exchanger: It also has a single boiler system but there is also an additional tube within the boiler. When a barista pulls a shot, the water flows from the water source through this tube located in the boiler. This is good because the water is fresher since it comes directly from a water source and isn't sitting in a boiler and it uses less energy than a double boiler system since only one boiler needs to be heated - super good for cappuccinos and other milk-based espresso drinks but again there is no direct control over the water.  
    • Single Boiler: There is a single source of water (the boiler) for both of these activities. Single boiler machines are usually more affordable and less sophisticated in their design but there is a reduced ability to control temperatures if you're constantly cycling back and forth between steaming and brewing. You cannot both brew and steam at the same time. 
    • Single boiler/dual use (SBDU): This is the same as a Single Boiler
    • Thermoblock: A thermoblock is a metal block with embedded heating elements and a pipe for water. As the water travels along the length of the pipe it picks up heat from the block, exiting at the desired temperature. The water is in contact with the thermoblock for a short time, but in that time it can flash heat to temperatures high enough to generate dry steam.
    • Thermocoils: Similar to a thermoblock: a heating element embedded in metal runs alongside a water pipe flash heating the water. While the body of the thermocoil is usually aluminum, the embedded pipe may be a different material such as copper or stainless steel. The main difference between the two technologies is that thermocoils are one piece units, and thus don’t suffer from the leakage problems of thermoblocks. Some thermo coils are built into the exterior of boilers. 
  • Dosing: 
    • Auto Volumetric:  Feature that allows the barista to pre-program the volume of water for each extraction.  This is done by controlling the water dispensing time.  This allows for a measure of consistency and a “hands-free” extraction process.
    • Gravimetric:  Scales built directly into the machine (usually in the drip tray) that weigh each extracted shot for optimal consistency.  This feature also allows the barista to pre-program desired weights.  Also referred to as Brew By Mass.
    • Semi Automatic:  Espresso machine configuration where the extraction process is initiated and stopped by the barista.  Each espresso extraction will manually start and stop according to the barista.  Usually there is a shot timer built into these configurations to see the length of extraction.
    • Filter Basket: The filter basket is a metal filter that is designed to let extracted coffee through while holding back coffee grounds like any other coffee filter. However, a filter basket that is made for espresso rather than coffee is designed to operate under much higher pressures.
    • Group Head: The group head is located on the front of the espresso machine. It is the part of the espresso machine where water from the boiler is dispensed into the coffee filter basket.  A group head is commonly simply called the 'group.' You might also hear it referred to as the 'espresso machine group,' 'brew group,' or 'brew head’.  The two most common types of brew heads are:
      • E61 group: The E61 group head was designed in 1961; It's a design that is tried and true and is one that is used on many of our prosumer grade espresso machines. This style of group head allows for mechanical pre-infusion while also exuding a romantic espresso machine style.
      • Saturated group: A saturated group head is one that is surrounded in water from the boiler. Instead of a completely separate component, the group head acts as an extension of the coffee boiler, allowing for consistent water temperature throughout.
    • Heat Exchanger (HX) Machines: Uses a single boiler but can brew and steam at the same time. To have this capability, the boiler is always kept at a steaming temperature.
    • Manual Espresso Machine (Lever Operated): Lever-operated manual espresso machines not only make excellent espresso, but they are also beautifully crafted machines that make a distinctive impression on your coffee shop counter. This style of espresso machine employs a piston that is driven by manual pressure or a spring-loaded action. When lifted, the piston pulls water from the reservoir into a small chamber and then forces the water into a filter of ground coffee when the piston is lowered. A lever-style machine is quiet and simple to use, once you've mastered it. We recommend lever-operated espresso machines for environments where the barista and staff are highly skilled. Essentially, the skilled operator of a lever machine can attain a level of control and excellence over their shot of espresso that is more difficult with any other type of espresso machine.These machines require physical strength to pull a shot and come in two different styles. 
      • Manual Lever:  When it is raised, an opening in the brewing chamber draws in pre-heated water to saturate the grounds. The barista can control the length of pre-infusion, flow rate, and pressure by when they bring down the lever.
      • Spring-loaded Lever: Pulling the lever down causes the spring to compress and brings the piston up. This creates space in the brewing chamber for water to enter. The lever comes back up as the spring releases its tension. This causes the piston to push the water down and extract the espresso.
    • Portafilter: A portafilter (or group handle) attaches to the grouphead of automatic, semi-automatic, and piston-driven espresso machines, and carries a tamped puck of coffee grounds within its basket. It is usually made of brass or stainless steel for better heat retention and is attached by a plastic or wooden handle.
    • Prosumer Espresso Machine: A professional espresso machine built for the home.  These machines have some of the same characteristics and features as their commercial counterparts however are small enough to fit in a standard kitchen.  
    • Power Requirements (Amps, Voltage and Watts):  20 Amps or less and 120v or less.
    • Semi-Automatic Espresso Machine: Semi-automatic espresso machines are a favorite of seasoned baristas. With these machines, you will need to know how to grind, tamp the coffee in the portafilter, lock it in the machine, and time your shot as it brews. You also need to know how to steam your milk using the steam wand. Semi-automatic espresso machines require the most skills. We have found that most coffee shops with trained staff (i.e. barista), a semi-automatic machine is the way to go. Semi-automatic espresso machines require constant training and employees should be tested and monitored to make sure they can make great espresso-based beverages. 
    • Steam Boiler Size:  Capacity in liters of volume that the boiler for steam can hold.  The higher the volume the higher the capacity to steam.
    • Superautomatic Espresso Machine: Super-automatic espresso machines can be thought of as an all-in-one espresso beverage machine. This means the machine is automatically doing some or all of the work in making the espresso or espresso-based beverage. There are two kinds of Super Autos, a one-step or two-step.
      • One Step: The machine makes the whole drink, from start to finish all you do is push a button.
      • Two Step: The machine will make the shot and the staff will need to steam the milk using the steam wand.

    Super-automatic espresso machines are often found in quick-serve restaurants, gas stations, office buildings, and hospitals. We recommend a one-step super-automatic if you have a café or restaurant with untrained baristas, but still, wish to serve consistent high-quality espresso drinks.

    • Under Counter Espresso Machine: 
    • Volumetric Espresso Machine: A Volumetric or Automatic espresso machine is similar to a semi-automatic where the barista grinds their own coffee beans, tamps the coffee, and pushes a button to start the espresso shot, but the machine has a built-in timer that cuts the machine off after a certain amount of time. Automatic espresso machines are ideal when consistency is key. Volumetric programming gives the option of precisely dispensing a desired amount of liquid with the push of a button. 
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