Espresso Machine Components and Features

Guide to buying an espresso machine
Components and features

An overview of the most important espresso machine components and features.

Pressure Pump

The most important part of the espresso coffee maker is the pressure pump.

The minimum pressure to make espresso is usually considered to be 9 bars. A more powerful pump means a finer grind can be used, so unlocking more of the coffee flavor, though there is also a greater risk of over-extraction.

Beware of inexpensive espresso machines fitted with a "reciprocating" pump. They're cheap, noisy and only produce very high pressure under laboratory conditions.

Boiler

The boiler heats the water for the espresso. The material, weight, thickness and design of the boiler are important considerations since temperature stability is essential for making good espresso - a boiler made from thin stainless steel will fluctuate much more in temperature than a heavy marine-grade brass boiler. Usually, boilers are made of aluminum, brass or stainless steel.

Aluminum is cheap and lightweight, so it's used in all the low-end models. Since it heats fast, it's good for quick single shots. It can, however, leave a hint of a metallic taste in your espresso, it tends to corrode faster than other metals and a number of studies have linked aluminum to Alzheimer's Disease.
Steel retains heat longer and is therefore good for brewing repeated shots.
Brass, like steel, retains heat longer. Of all the metals, brass is usually considered to be the best material for temperature stability.

Another consideration is boiler size. Smaller boilers (3-5 oz.) heat faster and are great for 1 or 2 cups, but they generally require more recovery time and may not maintain temperature as consistently as a larger boiler. As a general rule, the more expensive the machine, the larger the boiler.

More expensive espresso machines may use a heat exchanger boiler. These take the water for brewing and steaming from different parts of the boiler to allow steaming without any wait time. An espresso machine without a heat exchanger boiler typically takes 20 seconds to 1 minute before the steam function is operational.

Beware of espresso machines using a thermo block to heat the water. Thermo blocks just don't compare to a real boiler in terms of temperature stability.

Portafilter

The portafilter is where you place the coffee before brewing. Because the grind and tamp of the coffee are so important, the design of the portafilter makes a big difference to the quality of espresso produced by semi-automatic machines.

There are two different types: the pressurized portafilter and the commercial-style portafilter.

Pressurized portafilters are fitted in the majority of machines under $450. They range from 49 to 54mm in diameter and are usually constructed of aluminum. By preventing water from flowing out of the portafilter until the correct amount of pressure has developed, they allow espresso to be made without the need to be overly concerned about the grind fineness and tamp pressure. The down-side is that they destroy any true crema.
Commercial portafilters have a diameter of 58mm which provides a larger surface area from which the espresso is extracted. They are more dependent on the grind and tamp pressure to provide the resistance through which the water flows, but can produce espresso similar to that served in most coffee shops if skillfully used. Learning to make espresso with a commercial portafilter requires patience for the first few shots.

Portafilters should ideally be made of forged brass to give them durability and to retain more heat.

Group Head

The group head is the component into which the portafilter is attached. The best quality group heads are made of brass which evenly distributes heat and reduces â€œhotspotsâ€ for more consistent temperature (essential for making high quality espresso).

Spring Valves / 3-Way Solenoid Valves

There are two main types of valve used on espresso machines: spring valves and 3-way solenoid valves.

Spring valves, often called coffee valves, are the simplest type. Spring valves tend to drip over time and then need to be replaced. Although cheap to replace, on many machines they are an integral part of the boiler and can be difficult to repair.
3-way solenoid valves (also known as a drip-free system) should last a lifetime with simple maintenance such as backflushing. They provide immediate pressure release from the grouphead once an espresso pull is completed, allowing the portafilter to be removed and the next shot to be prepared instantly. They also leave a dry puck, which means less mess.

Water reservoir

A removable water reservoir allows you to take all the water out of the machine so bacteria won't build up. Make sure the water reservoir is easy to remove and big enough for your needs.

Coffee Pod Compatibility

Coffee pods contain one shot of coffee pre-packaged inside a filter disc and can only be used in pod-compatible espresso machines.

Pods are great for convenience and cleanliness, but they also have a number of disadvantages. They are more expensive than grinding your own coffee, you can only make single shots, and you can no longer alter the grind, dose or tamp to suit your own preferences.