But, the first concept we need to talk about, is what Lance calls the “elephant in the room.” To him, pressure profiling isn’t the best term to use, because you can’t get pressure without input flow and resistance. In other words, without a puck of coffee, ground fine enough to create resistance when the water is forced through it, there would be no pressure! So, in this case, Lance feels like the term flow-profiling is synonymous, which will help us further down the line in understanding these concepts and applying them to our daily workflows.
In this video, Lance describes three sections of your extraction as it pertains to flow and pressure profiling:
- Pre-infusion
- Infusion
- Taper
Pre-infusion – This is literally the step before infusion. What happens in this step is that we blast the bed of coffee with water to fully saturate it, but at a lower flow rate, so that we aren’t really starting the extraction. The purpose of the pre-infusion is to prime the puck for the next step, allowing it to expand and filling channels that might occur.
Infusion – Infusion is when we ramp up to whatever pressure we are targeting. Lance prefers, with lighter roasted coffees, a lower pressure, targeting 6-8 BAR. This is because with lighter roasted coffees there is a lower puck integrity as compared to a darker roasted coffee, which can take even up to 10 BAR.
Taper – The taper phase is when we lessen the pressure, or flow, of the extraction throughout the pull as the puck of coffee is eroding. And this is where this video gets really interesting. As Lance says, when we extract espresso, and we force water through the puck, and coffee ends up in our cup, there’s less of it in the puck than when we started! The puck erodes through the shot, meaning there is a lessened mass and therefore lessened resistance.
In Lance’s opinion, and we tend to agree with him here, the requirement of many commercial espresso machines to hold a consistent 9 BAR of pressure through the puck during the entire shot was a terrible step backward for espresso. It increases the possibility of channels at the end of the puck, and raises the likelihood of bitters at the end of the shot.
This is where the Flair shines. Because of the completely manual nature of the Flair, we can easily taper shots as the puck degrades, which is a feature that’s nearly impossible to find in electric machines at the same price point.
We’ll leave the rest of the discussion, as well as the demonstration of Lance’s profile, for those that want to watch the video. But, as always, we hope you’ve enjoyed this educational foray into the world of espresso.
Until the next Espresso University video…