Espresso Machines Unplugged

Understanding the features and workings of your espresso machine.

An espresso machine is, quite simply, a hot water boiler and steam generator with one or more integral, pressurised, coffee brewing points. With the emphasis on maintaining an optimum brewing temperature the machines is designed to produce 1-1.5 fluid ounces of concentrated coffee liquor, by forcing hot water at a temperature of between 92-96 degrees Celsius at a pressure of 9 bar (130psi) for a duration of between 20-25 seconds.

Inside the machine

Boiler - A typical semi or automatic espresso machine comprises of a boiler (or boilers) to generate hot water at approximately 96 degrees Celsius and steam at about 120 degrees. This is achieved by an electrical heating element and heat exchangers which transfer the heat from the main boiler to fresh mains water as it is required at the point of brewing.

Pump - This takes water from the mains (or integrated tank) and passes through the heat exchanger to the point of delivery, the bar at a pressure of 9.

Electronic - Various values of electronic temperature and pressure switches for safe operation.

It is usually not every user has access to the inside of a espresso machine. This is high blood pressure, and access is limited due solely to qualified engineers.

Out of the car

Steam pipes -One or more steam pipes run from the steam boiler at about 120 degrees and end with a nozzle with 3 or more holes, in which jets of hot steam to froth milk production.

Hot water tap - This is used to pull out of hot water at 96 degrees Celsius for the increase of more espresso drinks.

Headquarters units - These consist of a distraction plate to break the flow of water and a rubber gasket. The seals of the filter in the head and neck prevents'water/coffee from seeping out.

Filter handles - Solid metal alloy filter handles that fit into the group head and contain the initial dry espresso coffee grinds. The handles have single or double spouts, to brew one or two drinks at a time respectively.

Dials and gauges - Indicating pump pressure, boiler pressure, water temperature and sometimes water levels.

Brewing buttons - These are either preset (automatic model) or on - off toggle buttons for controlling the duration of the brew cycle and consequently the amount of beverage in the cup.

Drip Tray - A tray used to collect spillages with a waste outlet leading to a small reservoir or drain pipe.

Heated top tray - An area used for cup storage. The cup warming tray is simply heated by natural conduction from the boiler and does not have an independent heating source. It is recommended that cups are stored bottom down (not upside down) so that the bottom of the cup is warmed, not the lip.

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