The "profiling" shots that work best for me have a real peculiarity:

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TIME.SEC  PRESS.BAR  FLOW.DESCRIPTION
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00 - 10    0 - 10    dwell
10 - 12   10 - 10    black ooze
12 - 14   10 -  2?   molten chocolate   
14 - 20    2? - 6    molten chocolate held steady
20 - end   6 -  3    blonding, but held steady
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Notice what is happening between 12 and 14 seconds -- I disengage the pump, but hold the lever just above the detente, so there is no spring pressure at all. The trapped air alone is doing the work for a few seconds. I assume this means the pressure drops like I show in the second column (with the ?); but I'm not sure. My goal is to keep the flow steady and stop it from gathering steam. This pressure drop, followed by a rise, is not something lever people or pump profiling people normally do (as far as I know); but it does seem to work to produce brews that are sweet but clear.

I have no idea if a conventional lever group can be coaxed into doing this.

The other key is grind and dose. I found that the CMA/Ulka combo has a huge amount of punch. Fill a double with 14 gram and set the grinder so the pump ramps to full 9-10 bar pressure before anything flows, and the grind is in the Turkish zone, with no perceptible granularity at all. To use an ordinary fine grained espresso grind, you need to overdose the baskets. Conventional doubles work best at around 18 to 19 grams, Faema singles at around 10 to 11 grams. You can use lower weights or coarser grinds if you don't ramp up to 9 bar, but not that much -- even without the motor, the CMA group pushes the water through the puck much more efficiently than any pump group.

This has an upshot: If you use conventional Italian 7/14 doses, you are going to extract every last caramel molecule out of the coffee and get something really sweet and thick. But since the water temperature drops over the course of the shot, the ultra-bitter overextracted taste doesn't happen. So doing it like this is going to give you ultra-syrupy shots. For the "acid head godshot" like the Geisha, you need to grind coarse and overdose.

The experience of trying to get consistent flow in the basket study I was doing at the same time as this review has left me with the impression that the flow early in the shot is unstable, in particular, the transition from dwell to full flow can change by a few seconds shot to shot even if you keep the dose and grind the same.

Ordinarily this is no big deal, you just cut the shot when it blonds, and the volumes will be roughly the same. Here I'm doing something different -- actually controlling flow, without worrying if the pressure is going up or down. It just happens that if I just focus on flow rate, it becomes natural to decrease the shot pressure at the 12 second mark and then pick it up again.

I had a chance to play with an LM Strada with the pressure profiler, and wasn't able to replicate these style shots. Actually, I wasn't able to do much of anything.

It has a neat setup where you profile manually, then set it to auto, where it will repeat your manual profile for the next shots. But there is one buggy thing about it -- the paddle wheel on the group operates as the setpoint on a PID controller set for PD control. The operator feel is that changes in the paddle accelerate pressure rises and drops rather than setting a straight pressure, so the whole thing feels kind of seasick and unstable, with the pressure rising and falling like the water against a pier.

I'm sure they'll figure it out and tweak it for better ergonomics, but for now, it's so hard to use that I failed miserably.

shadowfax wrote:As far as the Strega, what kind of dose and brew ratio are you using for shots with this pressure profile?

For the Strega, to use the regular espresso grind range, you have to overdose. But here comes the mystery, I'm running roughly 0.8 to 1.0 brew ratios, and they taste no more concentrated than the 0.6 to 0.8 you would get with the regular dose. There is a lot of water sloshing around in the group, and a lot of extra runoff after the cup gets pulled.

For the Esmeralda and all really light, acidic coffees, I use a grind that would require a down dose to 12 to 12.5 grams on a regular machine.

Glad I wasn't the only klutz on the profiling Strada. It came as a shock, since the regular one is really intuitive.