Pressure Profilin'

I drove down to Gimme Coffee today to test out my newest piece of geeked out gear: a Programmable Pressure Profiling Pump. This is a homemade gadget designed to replace the rotary or vibe pump in an espresso machine. In theory, it will allow the barista artist to "sculpt" the water pressure profile through both the initial "preinfusion" phase and the main "extraction" phase.

I was inspired to build this thing by many people. Among them is John Bicht at Versalab, whose M3x machine reportedly has full pressure profiling capability through a computer interface. John says that changes in extraction pressure of only 0.03 bar (!) are tastable on his machine. Then there's Jim Schulman, whose experiments with pump machines and levers have led to some fascinating insights on pressure profiling. And Sean Lennon, home barista and industrial robot designer extraordinaire, has generously coached me on many key engineering details.

With technical help from Tomas (Gimme's excellent macchinesti), and moral support from Kevin and John Gant, we got the contraption hooked up to a venerable La Marzocco GS2. That's Tomas working on the machine in the photo.

So how was the coffee? Well, at first it sucked big time. But with Kevin acting as head barista, we gradually tweaked, tasted, sipped, spat and tweaked some more. We raised the preinfusion pressure, we increased the preinfusion time, we raised the extraction pressure. By the end, the coffee was coming out pretty damn nice -- and Kevin was really late for dinner!

It's a little overwhelming working with pressure profiles. There are so many combinations of things to try. But I believe that with proper attention to barista technique, grind quality, water composition, brew temperature, machine cleanliness, and now pressure profile, we are freeing ourselves from the tyranny of mechanical limitations. The aim, of course, is not to remain obsessed with the espresso machine itself, but to have unfettered control of the espresso process. Then we can finally extract our best from any given blend or roast with unprecedented artistry.

So what exactly is this Profiling Pump? Well, in its present incarnation it's a combination of pistons, valves, sensors and electronics that I won't attempt to explain (but that's part of it to the right of the grinder in the photo). It'll be installed on the GS2 at the SCAA Gimme Coffee booth in Charlotte, so please come by, say hello, and check it out. We'll be right near the BGA booth, so you won't have to go far.

At the end of the afternoon we had plenty of coffee heaped up below our grinder. Jay's famous BGA ad in Barista Magazine (which showed a grinder heaped with ground coffee) had nothing on us! We tried not to waste, honest! :-)