The espresso machine is an important part of your home, restaurant office or cafe, will cost as little as $500 or as much as a small car and can contain technology from the 1950s though to the 21st century. Here we will give you an introduction to start you on the road to finding the right machine for your needs, and desires.
FOUR OPERATIONAL TYPES
Manual machines have no electric pumps. Instead, the power to push water through coffee is provided by the user via the classic lever mechanism.
Pros: Beautiful to look at at rest and when in action. Pre-infusion capable. Proven technology. Consistent dosing.
Cons: High extraction temperature (straight from the boiler), extraction pressure varies dramatically during shot, ever diminishing number of techs who are familiar with them.
2. Semi Automatic
An electric pump replaces the spring and lever to push water through your coffee and water is sourced from a boiler and/or heat exchanger allowing control over extraction temperature. Shot is initiated either by a push button or a lever on the side of the group head.
Pros: Robust, simple technology that also keeps a trained barista engaged with the extraction.
Cons: Less skilled baristas might struggle to multitask during extraction.
Also called volumetric, automatic espresso machines use small computers to dispense a programmed volume of coffee.
Pros: Consistent volume extraction. Baristas are freed to texture milk, charm customers, take orders.
Cons: Less skilled users think these machines automatically produce perfect coffee. Computers in hot, humid conditions don't always like being doused in wet coffee grounds, steam and milk.
4. Super Automatic
Extraordinary engineering allows these machines to grind, tamp and then dispense espresso shots.
Pros: Completely automatic
Cons: Lots and lots and lots of moving parts.
BOILERS - SINGLE, MULTI, HEAT EXHANGER
Contemporary espresso machines all use boilers to produce steam and hot water for espresso extraction. Over the past ten years a number of manufacturers have introduced multi boiler machines in a range of configurations to assist in extraction temperature stability. Here we will outline how they work and how to choose amongst them.
1. Classic Single Boiler Heat Exchanger
While it might look complicated at first glance, it really isn't! The problem to be solved is that an ideal extraction temperature is around 200degF but we also need boiling water to produce steam for texturing milk. The simple heat exchanger solves this by passing cold water through a tube that passes through the boiler containing hot water and steam. The cold water picks up heat as is passes through boiler and, with some precise engineering and setting the boiler temperature correctly, the end result is extraction water at or near the desired extraction temperature.
2. Multi Boiler - Wet Head
The multi-boiler espresso machine usually does away with the heat exchanger and simply dedicates one boiler at one temperature for steam and another (or more!) dedicated to producing water at the desired extraction temperature, The picture to the right is the La Marzocco wetted head design, so named because hot water from the extraction boiler floods the inside of the group head.