The Feel of Declining Pressure on a Manual Lever

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vze26m98
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#1: Post by vze26m98 »

Greetings-

There's a bunch of material on HB about declining pressure profiles for espresso, but it seems most of the discussion on how to achieve it focusses on automatic machines. Of course, achieving declining pressure during a pull is a simple matter on a manual lever, but I haven't found much about the finer points, if there are any.

I have a Pavoni Europiccola, and have been pulling coffees in the ristretto range of 65-70%. This with an MCAL basket filled with 16gm of coffee. My typical (single: no Fellini or double) pull goes like this:

Lift the lever and wait for 5 seconds. With the amount of coffee in the basket, I'll never seen drips at this stage, so 5 seconds insures the grouphead chamber is filled. I'm sure the wait could be shorter.

Pull down gently until I see the first drop(s). Wait 5 seconds for a preinfusion. Begin the pull.

Somewhere about halfway into the pull, it begins to get easier, and this is where I'd like some insight. In the past, I've let the pull go faster, which I presume is maintaining the same pressure with my hands. (Or perhaps I increase pressure with increasing force in the pull.)

Yesterday I let up on the pressure, and let the pull run longer. By how much I don't know, but my previous pulls have been in the 30-35 second range (exclusive of preinfusion), so longer than that.

So what should the hand feel be at this stage in the pull?

The resulting coffee was enjoyable, although inconclusively better or worse. I sense my beans (Howell Calabria Daterra) are at the end of their lifespan. (Gone tomorrow!)

Thanks, Charles

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homeburrero
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#2: Post by homeburrero »

vze26m98 wrote:Yesterday I let up on the pressure, and let the pull run longer. By how much I don't know, but my previous pulls have been in the 30-35 second range (exclusive of preinfusion), so longer than that.

So what should the hand feel be at this stage in the pull?
I won't pretend to have an expert opinion here, but can say that when I'm dialing in a new coffee I always try a long drawn out shot where I ease off the pressure and keep the stream small and steady, often pulling for well over 35 seconds. And I typically end up liking these shots better than shots where I keep the force high throughout and get a quicker pull and fatter stream.
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

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drgary
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#3: Post by drgary »

vze26m98 wrote:So what should the hand feel be at this stage in the pull?
What should the hand feel be when playing a musical instrument? This is one of the pleasures of a manual lever. You modify your technique a bit and taste the result.
Gary
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What I WOULD do for a good cup of coffee!

vze26m98 (original poster)
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#4: Post by vze26m98 (original poster) »

Such nice responses from Pat and Gary, thanks!

I came to the conclusion that if I noticed that less effort was necessary, I probably was using less effort than at the beginning of my pull. But as Gary said, it's all about the performance and the result!

Best, Charles

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[creative nickname]
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#5: Post by [creative nickname] »

This is mostly just idle speculation, as I'm not one of the physics geeks on here that could write you out an equation modeling the pressure in the piston chamber. But on my MCAL, I notice that the flow stays pretty steady, rather than accelerating as the shot goes on (as it would on a pump machine or a manual lever if I applied constant pressure). When I want to replicate that effect on a manual lever, I let the flow be my guide, lightening up my touch as necessary to keep the same rate of pour from beginning to end of the shot. The taste profile isn't identical (there are other differences between the machines, after all), but it does get closer to that classic MCAL shot-style.
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another_jim
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#6: Post by another_jim »

[creative nickname] wrote: ... When I want to replicate that effect on a manual lever, I let the flow be my guide, lightening up my touch as necessary to keep the same rate of pour from beginning to end of the shot.
This would be my two cents as well -- it is the guideline used by people profiling on lots of different machines.
Jim Schulman

vze26m98 (original poster)
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#7: Post by vze26m98 (original poster) »

"Same rate of pour" it is...

Thanks Mark and Jim