Pressure profiling, flow profiling, and a new rule of thirds - Page 5

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#41: Post by kwantfm »

Thanks for the great thread. I did some very low tech testing. I have a fully stock standard ECM Technika Profi IV with vibe pump. I've found that I can grind significantly finer than normal (50-60 degrees on an HG one, so about 10 notches on a 2014 version of the grinder) by extracting in the following manner:
1. Turn pump on;
2. Wait for the pitch of the sound of the pump to increase - indicating that the pump is now meeting resistance and pressure is increasing;
3. Take the lever to the midway position deactivating the pump;
4. Wait for coffee to start beading on the bottom of the filter basket;
5. Engage pump again;
6. Take the lever to the midway position to allow for a gradual reduction in pressure in the last phase of the extraction.

Mirroring what others have said in this thread, I've found that the shots are quite different using this regimen, with astonishing fruit/floral characteristics and good/pleasurable acid characteristics.

I pulled a Yemen this morning in this manner and starting tasting the apricots that people have alluded to.

So even with a stock standard E61 one can still play a little with pressure profile, allowing for significant changes in grind size and opening up a whole new world of possibilities.
LMWDP #602

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#42: Post by radudanutco »

kwantfm wrote:...So even with a stock standard E61 one can still play a little with pressure profile, allowing for significant changes in grind size and opening up a whole new world of possibilities.
Sounds interesting, providing that this middle position for a vibe pump and for an E61 does not harm anything!
Would you please give some timing info (total estimated duration of extraction, 'last phase of extraction')?


#43: Post by kwantfm »

The timing is a little off the wall. It's anywhere between 5-8 seconds for the pump to start changing tone, and can be 40-50 seconds dwell time before there are first drops before I turn the pump back on. Sounds insane but I've found the results to be delicious.
LMWDP #602


#44: Post by lennoncs »

Hi folks,
interesting conversation.
Bill certainly hit it on the head, flow and pressure... you can't have just one.

bostonbuzz wrote:Sean Lennon is building an extremely advanced espresso machine incorporating an elliptical gear flow meter that measures 30 pulses/ml flowmeter here. Custom espresso machine build

It's the AW CAPM-3 and goes for about $350.

This combined with servo actuated needle valves appears to be a perfect test bed for this under-explored flow profiling in the first third of the shot. But it will probably take another few months to complete!

The CAPM-3 is the sensor
JVS-10SLGFS is the flowmeter

Sean Lennon
Davisburg Mi.

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#45: Post by another_jim »

I've spent the last month doing two different kinds of shots on the Strega.
  • The first kind, my normal procedure, I let the pump get up to full pressure before I turn it off and let the puck preinfuse. For this I pick a grind and dose so I see the first drops after about ten seconds.
  • The second kind, I let the pump only ramp up to about 3 bar. Then I shut it down, let the puck preinfuse at this lower pressure for 10 seconds, Then I turn the pump back on to ramp up to full pressure.
  • In both cases, I let the lever engage and finish the shot with the declining spring pressure, which from this initial pressure level runs from 10 to 5 bar.
The result has been almost entirely uniform (of around 40 shots of each kind only two responded differently): The flow from the lower pressure preinfusion is faster, or one can use a finer grind. Either way, the taste is more extracted.
Jim Schulman

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#46: Post by samuellaw178 »

In the spirit of pressure profiling, I have came about this blog entry. It's probably the most detailed writing so far (Outside HB of course, didn't mean to take the credit away from Nicholas for this fantastic thread) and more systematically presented at that. Many of the points presented is in agreement with my own and others' experience.

Thought it would be of interest to many here:

p/s: editted to acknowledge the contribution by Nicholas through this thread. Was in a rush to share that article and it didn't sound quite right when I read it afterwards.

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shadowfax (original poster)

#47: Post by shadowfax (original poster) »

Sam, really interesting article. Seems to be in agreements as far as the extraction dynamics, but the author's preference (fast ramp, coarse grind, low temp) seems far from what I've liked with my usual coffee selections. Thanks for sharing the link.
Nicholas Lundgaard


#48: Post by jonr »

The thing gets tricky, if we want to change the pressure throughout the shot, since the resistence of the coffee bed changes.
Which is why you want automated (ie, precisely repeatable) profiling. I expect that pressure profiling is less important and less consistent in its effect on taste than flow profiling, but more data is needed.


#49: Post by Billc »

I think you are correct but throughout my testing I have always found anomalies. I have made equipment that performed precision pressure profiling, temperature profiling, and flow profiling. However it always comes back to the coffee (grind and tamp). As long as you are consistent (within a small range) with grind and tamp then these precision machines will work.

My latest endeavor is to monitor both pressure and flow at the same time. I have not figured all the the math out yet but it gives me some additional information about what is happening in the coffee bed.

To explain a bit more, with pressure profiling you control pressure via pressure sensor. Since the coffee determines the flow resistance, different grinds will produce different flow rates. Similarly with flow control one flow profile will produce different pressures with different grinds. Both are dependent upon each other but each explain something that is happening differently. Still goes back to grind and tamp to make consistent.



#50: Post by jonr »

I agree, for perfectly consistent taste, you want all the variables to be held constant (grind, coffee, roast, humidity, etc). What's not clear to me is that when a small, inadvertent change to some variable occurs (we know these always happen), what thing(s) can a machine measure and control to get you back to (as close as possible) the original taste. I like your idea of looking at both pressure and flow; you can derive instantaneous resistance (it varies throughout the shot), which might lead to something interesting.