Inside Domestic Espresso
MachinesThis article is designed to give
the average consumer some insight into exactly what goes on inside
the most common brands of domestic espresso machines; it is
up-to-date as of August 2006. Before reading this article you
should read http://www.coffeeco.com.au/articles/glossary.html in
order to understand some of the technical terms used in this
machines are not discussed.
The stock ULKA pump found in so
To begin with, the pump. 18 Bar, 15 Bar, 9
Bar...what's the difference? In reality, none. ALL the pumps used in
domestic machines are vibration pumps, usually made by either Eaton or ULKA,
and all of them are basically identical. As long as the
machine has a pump, you can ignore the "Bar" ratings.
The rating itself relates to maximum output under ideal conditions, but in
reality most domestic machines have extraction pressures between 9 to 13 bar at
Then comes the heating technology, and it's
here where fundamental differences which profoundly affect espresso
"Thermoblock" technology means that the water
is heated in a multi channel metal block with an exterior element.
In the "flat" thermoblocks used in most machines the interior water
volume is quite small, and stable water temperature is theoretically
achieved by adjusting the flow rate of water through the block, in a
similar fashion to "on demand" household hot water systems.
Practically speaking, the limited water volume of most domestic
espresso machine thermoblocks make them very temperature unstable,
which in turn makes it extremely difficult to achieve a good
espresso shot. An exception to this is the recently developed
Sunbeam EM6900 machine, see http://www.coffeeco.com.au/articles/sunbeam.html
By using a large, stainless
steel lined thermoblock and electronic temperature control in
the EM6900 machine Sunbeam have been able able to overcome most of
the limitations, leading to reasonable shot quality, but as yet
there are no other mass market machines using the same technology.
Of course, the Sunbeam thermoblock is itself a development of an
earlier Krups thermoblock.
Thermoblock steaming is accomplished by using
the pump to pulse small bursts of water into the superheated block,
which is then supposed to flash into steam. Again in practice steam
production tends to be feeble and "wet". Even the Sunbeam machine,
which has a dedicated steam thermoblock and separate pump, has yet
to be overcome this limitation.
Thermoblock machines in general are cheap, and
will produce average espresso and reasonable milk drinks
given good technique, but anyone who wants better than
average should avoid them. Another downside of aluminium thermoblocks is
that they corrode, giving them a limited lifetime
and introducing a fair bit of aluminium into your drink.
An aluminium thermoblock with
Inside the block. "A maze of twisty
channels, all alike."
A 900w stainless steel boiler as
used by Krups, Saeco etc.
An inside view of a 900W stainless
Krups thermoblock (note plastic steam valve, a common failure
||Sunbeam thermoblock; its debt to the Krups unit is
||Teflon lined aluminium boiler, made in China. The shape
of the future?
||Big, solid, heavy brass Rancilio Silvia
Boiler machines tend to fall into definite
Chinese made specials, they
can be anything from low volume stainless steel (120ml or so) to
250ml teflon lined aluminium.
Gaggia, which have a
proprietary aluminium boiler with 2 external heating elements and a
boiler volume of 120ml;
with copper element, boiler volume 180ml;
Marine brass with copper element, boiler volume 300ml.
All boiler types have sufficient
water volume to keep reasonable temperature stability throughout a
double shot. When heated to steam temperature, the limited volumes
of the smaller boilers can mean slightly less steam time and power,
but all have enough for average use. In my experience the larger
volume boilers have a faster "recovery time" between shots and that
bit of extra steam, so that you can produce 6 cappuccinos in 5
minutes for your dinner party.
Again in my experience the Gaggia
boilers tend to
corrode internally. They are an aluminium upper part attached to a
brass group, and the combination of dissimilar metals and hot electrically
conductive water creates a galvanic battery which simply eats the
aluminium. This can also happen with aluminium thermoblocks, which
is why some of the more upmarket ones are now lined with stainless
Finally, the larger brass boilers tend
to have higher power elements than the smaller stainless steel ones,
again giving better thermal stability and faster recovery.
300ml brass boiler.
The standard S/S boiler on the
left, and the Silvia boiler on the right. Big, isn't
Inside an 18 month old Gaggia
boiler. The aluminium top has corroded, the chromed brass base
is in perfect condition.
This close-up shows the extent to
which the metal has been eaten
Aluminium Boiler (120ml)
Stainless Boiler (180ml)
Brass Boiler (300ml)
Most Sunbeam Cafe
Krups 2000 & 4000
Saeco, Solis & Gaggia
Gaggia (all local
cheap machines (often available on Ebay.)
|Saeco Via Venezia
Napoletana & Junior
Lelit,Imat Mokita Series
Opera & Fenice
The GROUP is the bit of the machine that the
portafilter locks in to, where the water is pumped through a
"showerscreen" on to the coffee. All of the thermoblock machines
I've seen have aluminium groups with stainless steel shower screens.
The smaller stainless steel boiler machines also have aluminium
exterior groups and S/S screens. Gaggias have a brass group with a
S/S screen, brass boiler machines have brass groups with S/S
screens. Of all domestic machines, only the Rancilio Silvia has a
commercial brass group and S/S screen setup.
Portafilters and pressurized filter
baskets are another point of differentiation, with
(again) thermoblock machines tending to have cheap aluminium
portafilters and quality boiler machines chromed brass portafilters.
All this concentration on metal types may seem a bit strange, but
excellent espresso production relies on thermal stability of all the
components in the process. Copper and brass are best, which is why
you find them in commercial machines.
Chinese made machine has a plastic group and stainless steel
Rancilio Silvia group, solid brass with commercial
showerscreen and water distributor.
||Pressurized portafilters: Krups on the left, Saeco on
||Unpressurized portafilters: Rancilio commercial pf on
left, Saeco/Solis/Imat/Nemox unpressurized on
All the rest (as far as I could
tell) are aluminium, lightweight and cheap. There is a particular 3
lobed 53mm portafilter with pressurized baskets used by Sunbeam,
Breville and Delonghi which seems to be a Chinese
Both Gaggia and Rancilio use
commercial portafilters and baskets on their domestic machines, although
the recent Gaggia Cubika has an aluminium portafilter. Solis and Imat
have brass portafilters but non-commercial filter baskets. Saeco
uses its patented pressurized portafilter, made mostly of plastic
but with some brass, as does Krups on its higher end machines. The
Saeco portafilter pops up on other brands of machines such as La
Pavoni and Spidem, so it's a good bet that these brands are
"rebadges", Saeco inside another manufacturer's body design.
and pressurized filter baskets come in many guises, but they
basically have a single purpose: to allow the customer to get the
appearance of acceptable crema from stale, poorly ground supermarket
coffee. Rather than buy a machine with a pressurized portafilter or
filter basket, I would ALWAYS recommend that you buy a decent burr
grinder. See http://www.coffeeco.com.au/newsletter/september2004.html and
Solenoid "3-way" valves are only available on
high end machines, they relieve pressure in the portafilter
immediately after brewing so you can pull consecutive shots.
Machines with solenoid valves are always built to a higher standard, and the fact that
the valve is there tells you that the manufacturer
knows something about real espresso machine requirements.
Solenoid 3 way
Sunbeam Cafe Series (except EM6900), 53mm
All Krups, 55mm
All Breville, 53mm
All Delonghi, 53mm
All Saeco, 53mm
All Solis, 53mm
All Gaggia, 58mm
Nemox Opera, Fenice, 57mm
Nemox Junior, Napoletana, 53mm
Sunbeam EM6900 (58mm)
Gaggia Classic, Baby, Coffee
Gaggia Classic, Baby
Krups 4000 Series
get down to the hard part, what do I recommend, and
SILVIA Simply the best value, most
reliable domestic espresso machine in the world.
Superb build quality, commercial components, fabulous
espresso, great steam. MUST be paired with a
good grinder for best results.
GAGGIA CLASSIC & BABY
Good value machines with commercial
portafilters, enough steam for 2 cappuccinos. Excellent
"learners" machine for beginners. Use for 2 years, sell on
Ebay before problems start.
LELIT COMBI Non-commercial portafilters but excellent 300ml
brass boilers, solenoids, integral Lux grinder in the Combi.
The Combi (and Nemox Opera) are probably the best value for
money machines available.
EM6900 Two pumps, two thermoblocks,
great package deal (including training) and good espresso
production. Steam still needs a bit of work. Next generation
will probably outstrip all except the Silvia. Will disappoint
new users unless they buy the matching
SEB (02) 97487944
Imat, Quaha, Nemox http://www.lygonimport.com.au
COFFEE & CUBIKA Depending on price,
which can be extremely variable at this end of the market,
these machines can be a bargain. All Gaggia domestic machines
have the same boiler and group, only the extras vary. These
are the non-solenoid machines, the Coffee has a brass
|LASCALA BUTTERFLY Instead of spending lots of money on a built in Miele
Superautomatic (which is actually a cheap plastic rebadged
Saeco) why not get a decent machine and grinder combination
for less money, and at least 10 times the longevity? Not to
mention infinitely better
The single most important
thing to think about when contemplating a domestic espresso machine
is "Which grinder will I buy?" because if you are serious about
making espresso based drinks at home, the grinder is the most
important component. There is simply no substitute for fresh,
correctly ground coffee in espresso