The electric piston type espresso machine, produced
by companies such as La Pavoni, is very classy looking
and can actually be a lot of fun to use. Although some
folks are so enamored by their aesthetic appeal that
they put them up for shelf display, they are actually
capable of producing a pressure of 8-9 bar, the benchmark
pressure of a genuine espresso drink. Like the steam
boiler model, the water reservoir heats up to the appropriate
temperature for milk frothing. Just open the steam valve
and let the foaming begin.
The pressure for brewing espresso is achieved by pulling
on a hand lever which is attached to a piston. Pulling
the piston up brings water into the group, and pushing
it down forces hot water through the grounds in the
portafilter. (See image 2)
Advantages
--The user has precise control over pressure applied.
--Often a thermometer is included so that you know
when your water is at optimal temperature.
--The porta-filter is usually heavy-duty, like the
machine's hull.
Disadvantages
--Not just any ape can figure these out (this ape,
for instance, needed a long time to learn how to operate
one of these machines expertly).
--Some units can be quite loud during initial heating
up.
--The reservoir is one big boiler, so the unit can
often take quite some time to heat up (several minutes).
