I have been thinking about this for some time. In general we all tend to agree that lever shots just have something that so many pump shots are missing.

A lot of focus and guessing has been tossed around about pressure profiles, how it is under user control, etc.

I have a different theory that popped into my head after a day of espresso pulls at a NW espresso jam. I think it may be that once you cock the shot you are into a static temperature system, so the intra-shot (I think that is the term I want [during the shot]) temperature is very stable. I have often heard that intra-shot temperature stability is critical for clarity of flavor, and by having an isolated water source, that is what we have with levers. Might also explain that many of us have found that one pull is the way to go. More than one pull and there goes your isolation.

Am I on to something or just blowing hot water

Assuming that the Scace device accurately reflects shot performance on the Termazona/Brugnetti the temperature starts considerably below the target at the beginning of pre-infusion, reaching the target temperature after approximately 15 seconds. It maintains target within 1 to 2 degrees for most of the 25 seconds of the pull, dropping off about 4 degrees at the very end. It is an HX, so may have different characteristics than some other levers.

Interestingly it does produce very good espresso, even at temperatures considerably lower (2 to 3 degrees), and with substantially more temperature variance, than would be considered optimal on a pump machine.

My theory is that manual-lever baristas are maintaining not constant brew pressure but flow rate. We adjust our pressure on the lever, sometimes subconsciously, to keep the flow going. Extraction quality is in the flow, not in the pressure.

Try pulling a few shots "blind" -- literally-- and see how well you do. Close your eyes as you pull. Maybe even stop your ears with wax, like the shipmates of Ulysses. I can hear a good pull.

Regards
Timo

timo888 wrote:My theory is that manual-lever baristas are maintaining not constant brew pressure but flow rate. We adjust our pressure on the lever, sometimes subconsciously, to keep the flow going. Extraction quality is in the flow, not in the pressure.

Try pulling a few shots "blind" -- literally-- and see how well you do. Close your eyes as you pull. Maybe even stop your ears with wax, like the shipmates of Ulysses. I can hear a good pull.

Regards
Timo

ah now, I have noticed that of other manual baristas, but I always go for constant pressure, not flow. Now I do agree that I can often hear a good pull.

My theory is that manual-lever baristas are maintaining not constant brew pressure but flow rate. We adjust our pressure on the lever, sometimes subconsciously, to keep the flow going. Extraction quality is in the flow, not in the pressure.

Where does this leave the spring-driven lever's espresso, by comparison? How do results from a manual lever and spring lever differ, all else being equal?

grong wrote:

My theory is that manual-lever baristas are maintaining not constant brew pressure but flow rate. We adjust our pressure on the lever, sometimes subconsciously, to keep the flow going. Extraction quality is in the flow, not in the pressure.

Where does this leave the spring-driven lever's espresso, by comparison? How do results from a manual lever and spring lever differ, all else being equal?

In a Peppina vs Caravel grudge match ...
-- both gravity-fed open-kettle temperature-stable machines
-- both give you control over the preinfusion
-- Peppina's spring is unforgiving: you either have a grind that is within the sweet range or you don't
-- Caravel you can finesse somewhat and compensate for too coarse a grind with a gentler pull, for too fine a grind with a harder pull, letting up, and then pulling again; too much unrelenting pressure stalls the flow (as Illy points out)

It's possible to pull excellent shots from both.

Easier to change beans on the Caravel with fewer sink-shots. Since you can compensate mid-pull on the Caravel, shots where the grind isn't dialed in yet are still drinkable.

The spring was better suited than a manual lever to a commercial establishment (or to entertaining dignitaries and such at home) because it left the barista's hands free to multi-task.

In terms of taste, the difference resides in constant pressure versus variable pressure. No matter how robot-like the manual-barista may think his technique is, the pressure will vary quite a bit. It can ramp up quickly or slowly, it can oscillate and falter -- all of which can be virtues or vices.

The manual lever is a stringed instrument without frets. The spring lever, one with frets.

Regards
Timo

timo888,

Thanks for your lovely reply.

grong

timo888 wrote:My theory is that manual-lever baristas are maintaining not constant brew pressure but flow rate. We adjust our pressure on the lever, sometimes subconsciously, to keep the flow going. Extraction quality is in the flow, not in the pressure.

This theory is still in the running. Andy found the best profiles from his within-shot pressure profiling system came from ones that came close to constant flow. However, the result wasn't better taste clarity, but much better mouthfeel. Since this tends to be a weak spot on levers; I'm not sure where we stand.

As Dan posted, I'm still scratching my head about how taste responds to extraction. There's a few simple ones like "if it's sour go hotter and slower, etc" but other than that, most of the the theories don't wash. I got two silvias for side by side tests, and a lot of food dye to get traces of water paths through the puck, but I've done absolutely nothing in the way of research. I'm still enjoying the shots from the Elektra too much to get all analytical.

another_jim wrote: . . . Andy found the best profiles from his within-shot pressure profiling system came from ones that came close to constant flow. However, the result wasn't better taste clarity, but much better mouthfeel. Since this tends to be a weak spot on levers; I'm not sure where we stand.
. . .

For clarity of delicate floral notes, the honors in my house must go to a Papua New Guinea roasted Full City pulled lungo and so gently on the Caravel it barely cleared the bar for espresso. It was the very opposite of mousse in the mouthfeel and the crema was not robust, but I was as high as a hummingbird on the first sip.

Regards
Timo