E61 Brew Group on the Izzo
As we wait for the Rocket R58 to join the Izzo Duetto II in our office later this month, I thought
perhaps now would be an opportune time to examine just what these double boiler
E61 machines are bringing to the market.
The E61 Brew Group has been
hailed as the industry standard since its inception by La Faema in 1961, but it
has steadily been overtaken in recent years by the newer Saturated Brew Group
design. The brewing group is open to the brew boiler itself in saturated groups,
which results in improved temperature stability due to the group being saturated
with the same body of water whose temperature is being controlled in the boiler.
This design is only possible, however, with machines that have separate steam
and brew boilers such as the La Marzocco GS/3 and La Spaziale Vivaldi II series.
Before saturated groups
were invented, almost all espresso machines could be found utilizing some
variation of the original E61 group head, despite it being a 50 year old
technology. Interestingly enough, dual boiler systems are now coming out that
utilize the older E61 design, the Izzo Alex Duetto II and Rocket R58 being
perfect examples. Both machines, in fact, are completely PID controlled, a
modification that is not possible with traditional E61 heat exchangers.
Although the E61 has been
superseded by saturated groups in high-end commercial use, their temperature
stability and tried and true design, especially when combined with double
boilers, make them an excellent choice for use in a low volume, home
environment. With this being the case, what choice are you actually making when
choosing between the two brew group designs?
Saturated Brew Group on
the La Marzocco GS/3
Before independent brew
boilers were available, the E61 group achieved thermal stability through the
eight and a half pounds of chrome-plated brass that it was physically molded
from. This is the reason why the brew group takes around 30 minutes to both heat
up and cool down. Even though the group provides a thermally stable environment
at the head, the user still has to compensate for the relative unpredictability
of the actual heating element within the machine. Users of a heat exchanger are
well aware of the necessity to bleed the group prior to pulling a shot in order
to reduce the temperature of the water within the system. As you continue to
pull shots, the water will steadily deviate from the optimal temperature range
and eventually exhaust itself. A saturated group, on the other hand, pulls water
from a dedicated and thermally controlled water source. Depending on the size of
the boiler, the water should remain at a consistent temperature over the course
of multiple shots. Double boiler machines have quickly become the industry
standard for this very reason.
We will soon be conducting
thermal stability tests between the two boiler types. Due to its design, the E61
may still require a purging/warming flush even when paired with a dedicated brew
boiler. If this happens to be the case, I would still expect to see a general
increase in shot workflow and stability. We’ll post results when we have
While specific engineering
aspects of these two systems is beyond the scope of this article, there are
several excellent threads on Home-Barista that explore both the E61 and Saturated group systems.