With all the quarantine going on in Massachusetts, its been a fantastic time WFH and able to make a lot of espresso every day. I had the opportunity to try an E61 espresso Machine from Quickmill, with a pressure profiling knob!
The core of the E61 Group Head was filed in 1961 and looked akin to this:
The basics of this group head hasn’t changed significantly in the many decades since.
These group heads are considered a common commercial group head. They weigh around 9lbs, and have a method for cycling hot water from the boiler to the group head. These group heads are very robust and can be used in their single boiler or double boiler systems.
In terms of Pressure profiling, the best way to view it is as flow profiling. A knob on the top of the group head adjusts the size of a needle valve, changing the amount of water that can go to the espresso puck. The amount of water currently pressed against the puck determines its pressure, and the differential between the water in and water out determines the pressure.
What does it mean for the user? Well it makes it so that the espresso pump, which is normally at around 9 bar, doesn’t instantly flood the puck with 9 bar of pressure. Despite the fact that a lot of e61 group heads already have a valve that slowly ramps the pressure, this system allows for much more fine grain control. In addition, the ability to adjust the pressure allows for more interesting brew recipes. For example, I found I like some of my espresso blends brewed at lower pressure. Finally, it allows on the fly adjustment of brew parameters, such as total extracted volume. All in all, its a great toy that allows for loads of fun and tinkering. I’d highly recommend it!