I'll be setting up a Versalab M3x in a client's home this summer (as soon as the machines are available.) Precisely defined pressure profiles are outside my experience, though. Has anyone experimented with pressure curves? I didn't see much in my Illy book & I don't know of any equipment currently capable of this other than direct lever machines.

Thanks.

pdx wrote:I'll be setting up a Versalab M3x in a client's home this summer

That is great news.

pdx wrote:Has anyone experimented with pressure curves? I didn't see much in my Illy book & I don't know of any equipment currently capable of this other than direct lever machines.

I know of one or two people (not Versalab) who are planning to bring pressure profiling equipment to the Charlotte show. It appears to be pretty much uncharted territory -- although Michael T will undoubtedly tell us that the Italians developed it 15 years ago but never put it into production.

Many people, including me, think lever machines give a cleaner taste than pump machines. This could be due to any number of factors; but a standout possibility is the spring lever's pressure profile -- a very low pressure (1 to 1.2 bar) preinfusion for 10 seconds while the lever is held down, then up to 7 to 9 bar suddenly as the lever is released, then declining linearly to about 4 to 6 bar from 10 seconds to 30 seconds into the shot as the spring uncoils.

This could easily be programmed into the M3x.

Another more complex profile, requiring investigation is based on the observation that the flow rate gets higher as the shot progresses and the puck loses material. If the pressure is reduced during the shot (even more strongly than in a lever machine), it may be possible to keep the flow rate steady. I have no justification for this procedure other than its appeal to my sense of tidiness; but it also has the merit of being simple to observe and explain. This may make it a good starting point for investigations of pressure profiles.

another_jim wrote:Many people, including me, think lever machines give a cleaner taste than pump machines. This could be due to any number of factors; but a standout possibility is the spring lever's pressure profile

I think that this is where I'll get a starting point for experimenting with pressure. My first machine was a Pavoni. I definitely learned from the direct control of pressure. (Ironically I ditched the Pavoni for my Tea based largely on your alt.coffee review a couple of years ago.)

another_jim wrote:Another more complex profile, requiring investigation is based on the observation that the flow rate gets higher as the shot progresses and the puck loses material. If the pressure is reduced during the shot (even more strongly than in a lever machine), it may be possible to keep the flow rate steady.

Interesting. Is there a precise means of measuring flow rate or would this be a visual exercise?

It sounds like the machine allows storage of many profiles and will produce printed records that can be kept with subjective taste notes. This'll be fun.

I've experimented quite a bit with pressure profiles. At first it seems great, you'll see taste differences changing just a tiny bit. As with all espresso, it's so subjective, I don't think you'll ever get too many to agree on which profile tastes best, after blowing through umpteen pounds of different roasters blends I find myself liking most the simplest curves, mainly in the front, say 3 sec. to full pressure, and no ramp down at end, just pull it. To my taste, this seems to be the richest flavor. Now if you take and feather the last of the shot, one characteristic that seems to always be is a "rounding" of the flavors that could maybe be described as a lighter cup. I have found that any fancy up, down in the middle of the shot doesn't (at least to my taste) make it better, just different.
One thing for sure, you'll have a lot of fun testing all these possibilities. I hope you have a good roaster friend, it's going to get expensive

pdx wrote:I think that this is where I'll get a starting point for experimenting with pressure. My first machine was a Pavoni. I definitely learned from the direct control of pressure. (Ironically I ditched the Pavoni for my Tea based largely on your alt.coffee review a couple of years ago.)

Sorry. I agree with what Jepy said. I go back and forth between my peppina and tea. When I go to the Peppina, I'm happy with how much clearer the coffee flavors come through. When I go to the Tea, I enthuse about the syrupy body and clotted cream like crema. In my experience with other machine's shots, I've lucked into a pair of machines that are at the extreme ends of the spectrum on this which is kind of fun.

Interesting. Is there a precise means of measuring flow rate or would this be a visual exercise?

I'd start by eyeballing. If you start by measuring, you'll certainly want to close the loop, and end up with the M3x-PDX

another_jim wrote:Another more complex profile, requiring investigation is based on the observation that the flow rate gets higher as the shot progresses and the puck loses material. If the pressure is reduced during the shot (even more strongly than in a lever machine), it may be possible to keep the flow rate steady. I have no justification for this procedure other than its appeal to my sense of tidiness; but it also has the merit of being simple to observe and explain. This may make it a good starting point for investigations of pressure profiles.

Probably the "flow rate profile" depends on a lot of factors, and it may prove deceptive to make generalizations about it across various coffee/machine/technique platforms.

This morning I did a variation on the old "divide a shot into thirds" technique. I divided 30 second shots into six equal time portions (0-5 sec, 6-10 sec, 11-15 sec, 16-20 sec, 21-25 sec, 26-30 sec), and weighed each portion. The graph below shows the result of three extractions using Riley's Espresso Taliaferro, 17 gram doses, LM ridged basket, LM GS3, 199F, ~9 bar. The result doesn't exactly display "flow rate," it's more like "mass flow rate," but it's a different profile from the one you're observing.

AndyS wrote:Probably the "flow rate profile" depends on a lot of factors, and it may prove deceptive to make generalizations about it across various coffee/machine/technique platforms.

This morning I did a variation on the old "divide a shot into thirds" technique. I divided 30 second shots into six equal time portions (0-5 sec, 6-10 sec, 11-15 sec, 16-20 sec, 21-25 sec, 26-30 sec), and weighed each portion. The graph below shows the result of three extractions using Riley's Espresso Taliaferro, 17 gram doses, LM ridged basket, LM GS3, 199F, ~9 bar. The result doesn't exactly display "flow rate," it's more like "mass flow rate," but it's a different profile from the one you're observing.

Your shots appear to rise linearly in the first 25 seconds, but then it evens out. That may be true for my shots too; the crema gets coarse at the end and may be deceptive for eyeballing volume. I'll repeat this drill later this week on my machines and see what gives.

another_jim wrote:Your shots appear to rise linearly in the first 25 seconds, but then it evens out. That may be true for my shots too; the crema gets coarse at the end and may be deceptive for eyeballing volume. I'll repeat this drill later this week on my machines and see what gives.

Looking at the graph makes me think that a declining pressure profile (DPP) might keep the mass flow rate fairly even through the middle portion of the extraction. At the end, the puck is nearly spent, so there is less material being extracted and the mass flow drops. With a DPP the mass flow would drop even faster, but this is when you'd typically cut off the shot anyway.

For the first 10 sec or so the fines are migrating and you wouldn't want to try and equalize mass flow even if you could.

It would be great to superimpose the data from the flow meter on top of this graph (which Bill C could do, but not I). There's a rush of water at the beginning that fills the empty spaces, then it evens out. It's possible that the water flow into the puck remains fairly steady at the end, but since there isn't much left to extract, the mass coming out decreases.

This is very interesting, Jim, I've got my pressure profiling pump working fairly well now and I should be able to try and equalize mass flow via the DPP. Not on the GS3, though (0.6mm gicleur interferes with pressure profiling), just on good ole Silvia.

I'm looking forward to seeing the results you get comparing Tea to Peppina.

AndyS wrote:Looking at the graph makes me think that a declining pressure profile (DPP) might keep the mass flow rate fairly even through the middle portion of the extraction. At the end, the puck is nearly spent, so there is less material being extracted and the mass flow drops. With a DPP the mass flow would drop even faster, but this is when you'd typically cut off the shot anyway.

It would be great to superimpose the data from the flow meter on top of this graph (which Bill C could do, but not I). There's a rush of water at the beginning that fills the empty spaces, then it evens out. It's possible that the water flow into the puck remains fairly steady at the end, but since there isn't much left to extract, the mass coming out decreases.

Fascinating data, Andy - thanks for posting it! But you have only one data point that shows mass decreasing at the end. Do you think the volume-mass ratio changes significantly throughout the extraction? I'd guess espresso weighs just about the same per unit volume as plain water, and would expect the mass flow to level off for a constant pump pressure.

- John