"BEST PRACTICE" espresso profile now available.
I've been working on a "best practices" espresso profile, incorporate the best practices we've found in the five years we've been shipping the Decent Espresso machine.
I'm very much looking for a better name, but I'm not going to name it after me (some people suggested), as all I've done is poach 3 other people's good work (Damian Brakel, Scott Rao, Jonathan Gagné) and merged it into one unified profile.
Here is what I think is "best practice" about this profile:
- quick fill of group head at the start of preinfusion
- low pressure preinfusion, to assist capillary action in fast, even wetting
- slightly softened pressure rise to avoid channeling that a hard rise can cause
- extraction phase switches to flow profiling, for automatic channel healing.
- extraction phase has a linear flow rate ramp up over time, to keep constant water contact time, instead of using pressure profiling to approximate this
- extraction phase uses pressure limiting, so as to never go above the set max pressure (9 bar)
- the extraction phase decides the end-flow rate relative to flow at peak pressure. This adapts the profile to the grind size (not yet implemented) -- this comes from Gagne's work.
- accurate stop-at-volume closely matches scale weight, because of a fully successful preinfusion
- a smooth puck resistance curve is achieved
Some of the "best practices" here were originally discovered on traditional machines:
- several machines (such as Kees's Idromatic) have a quick fill, followed by a soft-pressure-rise feature built into the group, and manual lever users have done this for years
- pressurized preinfusion is fairly common in traditional machines, but to my knowledge, no traditional machine implements this by measuring puck pressure. Instead they measure pressure-behind-a-flow-constrictor, which gives different results.
Here is a photo using this profile. The traces behind are my Londinium god-shot, which was my reference to try to imitate, but hopefully improve.
Things to note about my shot pull that are different than the Londinium god shot reference:
- the pressure rises both start at 0:12 but the "best practices" profile takes a few seconds longer, and has a linear pressure rise
- the flow rate down/up bump of Londinium, which occurs as max pressure is hit, is mostly gone with this profile
- pressure has a flick up around 0:25, due to fines migration, visible now due to the constant flow. With Londinium, this fines migration is visible as a flattening & decreasing of the flow. The extraction theory I'm adhering to doesn't think that the flow rate declining in a shot, is a good thing, so this is the biggest difference between Londinium and Best Practices profile.
This profile is now in the 'nightly' build of de1app, or make it by hand with the images below.
Note: I have not yet implemented the "mutating" aspect of this profile, which is to have it change the final goal flow rate based on the flow rate at the end of the "pressurize" stage. It's currently set manually (default: 2.2ml/s) and you'll want to adjust this so that it's (in my experience between 0.5ml/s and 1.0 ml/s) more than the pressure you observe at peak pressure.