Espresso Coffee Machine

 

Working Principle

The ground coffee is tamped into a filter that is situated in the group handle. The group handle is then inserted into the group head. The Espresso Coffee Machine filters pressurised hot water through the filter, therefore filtering water through the coffee ground. The water temperature is approximately 92 °C (+- 5), and is forced through the filter with approximately 9 Bar.

An Espresso Coffee Machine works in a similar way as a filter (drip brew) machine. The main difference is the pressure and the temperature control.

The pressure quickens the process of making coffee and can produce different flavours of coffee.

Temperature Control

The brewing temperature is extremely important. A good Espresso Coffee Machine controls the temperature at all times.

The temperature in a boiler can rise when the machine is not used for a while. It can also drop quickly when a lot of water is dispensed, e.g. with a pot of tea. This will change the brewing temperature, which will then change the flavour of the espresso. It is therefore that many new machines have multiple independent boilers.

Amount of water

The amount of water that is filtered through the coffee is extremely important. The fully automatic machines have pre-set buttons. There are usually 4 buttons for each group head. These buttons can be programmed to dispense a desired volume of water.

The button displaying one cup is usually set to 25ml, one single espresso. The button displaying two cups is set to double that amount. In Italy the one half-full cup is usually set to 15ml for Ristretto’s, however, in England it is usually set to 25ml.

For group handles with one spout the one-cup button should be selected and when using the group handle with two spouts, the two-cup button should be selected. It is very important that the correct button is selected. The star button is a manual button and will let the water flow until pressed again to stop.

 

Steam Wand

The machine has a steam wand, which produces steam for steaming the milk. The pressure for the steam should be around 1 Bar. The higher the temperature in the boiler, the higher the pressure.

Hot Water

Hot water comes from the main boiler and usually has a temperature of approximately 95 °C.

Cup Warmer

The top of the machine has heated shelf space for cups.

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