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 supply
(or integral tank) and passes it through the heat exchangers to the
point of brewing operating at a pressure of 9 bar.
Electronics – Various electronic pressure and
temperature values and switches to ensure a safe operation.
Due to the high operating pressure of the pump and boiler, there
are no user adjustable parts inside the machine and access is
restricted to qualified engineers.
Outside the machine
Steam Wands – One or more steam wands draw
steam from the boiler at approximately 120 degrees and terminate
with a nozzle with 3 or more holes where jets of hot steam issue
from to foam milk.
Hot Water Tap – This is used for drawing off
hot water at 96 degrees Celsius for topping up espressos into
longer drinks.
Group head assemblies – These comprise of a
dispersal plate to break up the flow of water and a rubber sealing
gasket. The gasket seals the filter handle into the head and
prevents the 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.
It is warmed naturally from conduction from the boiler. It is
recommended that cups are stored bottom down (not upside down) so
that the bottom of the cup is warmed, not the lip.
Written by Fenton Wayne - (Fenton Wayne is an independent advisor
in the coffee and vending trade where he has over 25 years
experience. This article has been submitted to and distributed
by www.submityourarticle.com)