The fundamental principle of filter coffee is
simple: a basket, usually conical, lined with a porous filter.
Finely ground coffee is added to the basket, hot water is then
poured, sprayed or dripped on to the coffee and the extract drips
through the filter into a container below. Practically speaking,
these days there are two different types of filters used in manual
or automatic brewers.
The filter types
are paper filters, a direct adaptation of standard filter papers
used in chemistry laboratories, which can be folded to fit a cone or
come in various pre moulded shapes; and "Gold" filters, fine metal
or plastic meshes usually built into the cone itself. Manual brewers
can be as simple as a plastic or metal cone which sits on top of a
cup, or as complex as a 12 cup Chemex glass brewer looking as if it
escaped from a nearby lab.
Electric filter machines usually consist of a
tank with a heating element, a water distribution system, a cone to
hold the filter and the coffee, a carafe or jug of some sort to
receive the brew and a hotplate to keep it warm. They are big
business kitchen appliances and there are a number of bells and
whistles added to various machines, including timers, settable
thermostats, milk steamers and internet connections. (Internet
connections are pretty rare at present, but they DO exist, although
not on home appliances.)
When it comes to the different
filter types, paper or mesh, my personal preference is always for
the mesh type. Paper filters preferentially retain the coffee oils
which carry flavour and aroma, and for me this always means that the
resulting coffee lacks something. The mesh filters do not hold back
anything from the coffee extract, but may produce more sediment
depending on how finely the coffee is ground.
A correct filter grind is finer than that for
plunger, but not quite as fine as used for an espresso pot. The
coffee to water proportions are critical, as is the temperature of
the water used for brewing. Below are some guides to getting the
best out of your filter brewer.
1) Use 10g of finely ground coffee per 180 ml
2) If you're using a paper filter, wet it with a
splash of hot water before adding the coffee. This will cut down on
the absorption of coffee oils into the paper.
3) Smooth out the coffee so it sits in the
lowest part of the filter.
4) Bring your hot water to the boil, then remove
the heat immediately. Wait 30 seconds for the water to cool to 95°
C, then pour a little onto the coffee to wet it thoroughly. Continue
pouring your water into the cone, making sure that it does not
5) When all the coffee has dripped through into
the jug, remove the filter and serve immediately.
In my experience the definition of a "cup"
depends on who makes the machine, and even then varies between
models. You need to check the ACTUAL brewing capacity before you
begin, then proceed as for steps (1), (2) and (3) above. A wise
buyer will also determine the temperature of the brewing water as it
exits the water distribution system, as many cheaper models tend to
brew below the optimum 95° C level, resulting in thin,
Again, I would prefer a machine with a permanent
filter to one that uses filter papers; you get better flavour and
pay much less in the long term for your brewing pleasure. However,
Melitta, the inventors of filter brewing, have recently released
special ‘micropore’ filters which absorb less oils, so if you're
stuck with papers you might want to try these.
One thing to be careful of with Filter machines
is the hotplate. Leaving coffee on the hotplate for longer than 30
minutes will result in a typical stewed brew. Another caution is
that very fresh coffee in some poorly designed machines will produce
so much froth that it will spill over the filter basket when you try
to brew at the full capacity. The only solution is to drop back to
around 75% of the nominal "full" brew.