samuellaw178 wrote: One thing seems odd though - by adding up the numbers, it seems that they're pulling rather fast shots from 18-23 sec? Unfortunately the brew ratio wasn't mentioned. I normally pull shots between 35s-45s so this is quite interesting.

I had also noticed that: 23 seconds is well under what I normally pull on my lever. My normal time range is pretty much on par with yours.

tohenk2 wrote: Maybe a coincidence, but my shots also run around 23 seconds If I use a profile like this. Depending on the coffee, it can get to 30 seconds.

At Valentine (the shop with the Synesso Hydra) they follow this profile rather closely but the barista said he pulls their shots around the 25 second range, maybe a little longer for lighter coffees. Those guys have been running that Hydra for years and know how to play it rather well. Since their times correlate more with yours this could be a pump vs lever thing.

samuellaw178 wrote: There were also quite a few insights/observations there along the way in that document (flat burrs vs conical burrs, drips during preinfusion, difference between low & high preinfusion pressure etc etc - things that I have no clue about). Great stuff!

I found the burr geometry section interesting as well but I'm curious how they "know" that.

Ellejaycafe wrote:another thing I'm learning with the lever is to not worry about the time as much and concentration on pressure and flow.

Agreed. I've also noticed that if I focus on a certain flowrate into the cup the time becomes less important of a measure. Also, I'm glad you are enjoying success with your lever. I have greatly enjoyed the pictorial threads of your custom machine, it's one of the coolest looking I've seen.

homeburrero wrote: One thing in their "Tiny bit of background info" has me confused. They state the following:
"The spring's potential takes a small amount of time to be realized as it is not as strong initially as a rotary pump."

I would think it would be the other way around - i.e. that the brew chamber pressure on a spring lever is near instantly at the maximum when you release the lever. Whereas on a rotary the pressure at the gauge (which is on the pump side of the gicleur) would quickly hit the pump's max, but inside the brew chamber it would rise a little more gradually because of the gicleur (plus also because of the pre-infusion chamber in the special case of an E61.) Am I missing something?

Of course, as Dominick points out in his other thread, the ~6 bar "secondary preinfusion" effect can be accomplished on a spring lever if the operator slowly releases the lever and retards its upward progress for a few seconds before fully letting go.

Right, the only thing I can think of is that they had an initial assumption that the barista is supposed to lift the lever slowly when they pull the shot. Otherwise why create a 2 stage preinfusion as an attempt to mimic a lever? Serendipitously this assumption provided me with another profiling technique to use on my lever.

I certainly found this article informative and potentially game changing for me, especially dealing with lighter roasts; I hesitate to declare anything in the article as solid fact however; as they stated themselves they didn't follow any scientific rigor with these experiments other than to measure the TDS of their shots.
So consider this qualitative at best.

Gave the recommended pressure profile a go this morning. Pulled about 6 shots so it's a preliminary impression at best.

With the recommended profile, I do not know how it is achievable without getting a gusher. My usual brew ratio is 2:1 normale but I can hardly achieve ristretto with this profile (even after coarsening the grind). The recommendation was to not see any beadings during initial infusion - this means the grind must be fine enough yet able to yield whatever brew ratio you targeted in 19 sec (excluding the 4 sec infusion).

Interestingly (in an unexpected way), the crema came out more macro rather than champagne mousse cited. It's almost like a milk not well-steamed with grainy textures. Back to the default spring lever profile that I normally use, what came out is indeed champagne mouse with no visible crema bubbles at all (silky came to mind! Plus there're a few feline spots if you're into that ). That, to me, shows that pressure profile does in fact influence the emulsion texture quite a bit (I guess a big part of it might have been the flow rate).

In my experience, the best outcome from the lever is usually obtained in its default pressure profile mode, where the grind is tuned-in (rather than manipulating the pressure profile) to achieve the desired flow rate. But the ability to manipulate pressure gives more headspace/flexibility for certain finicky coffees.

It's quite funny how pump tries to imitate lever, and now we lever users (me at least) try to imitate pumps.

dominico wrote: I found the burr geometry section interesting as well but I'm curious how they "know" that.

I certainly found this article informative and potentially game changing for me, especially dealing with lighter roasts; I hesitate to declare anything in the article as solid fact however; as they stated themselves they didn't follow any scientific rigor with these experiments other than to measure the TDS of their shots.
So consider this qualitative at best.

Yeah indeed, it is an observation-based report. But still a worthy one since they're confident enough to document it and share publicly. It's similar to science experiments/researches - you won't get a single perfect data but all the data points add up to give a whole picture - I consider this as one of the many data points. About the flat vs conical observation, it does seem odd they use 'pure' to describe the grind. But it is still a valid observation without involving microscopy/laser diffraction techniques.

Also, since they're measuring TDS (reporting as high as 20% increase) instead of extraction yield %, I wonder if the TDS increase were due to shorter shot volumes?

Excellent presentation Dominick!

samuellaw178 wrote: With the recommended profile, I do not know how it is achievable without getting a gusher.
... It's quite funny how pump tries to imitate lever, and now we lever users (me at least) try to imitate pumps.

my Strega has all the usual mod's: a pressure gauge on the pump exit, a PID on the group heater, a switchable dimmer on the pump;
any pressure profile until the springs take over the brewing, seems to be achievable: steady - from 0 bar resting to any bar value - hence steped PI, ramp, slope; consistently enough due to the gauge; and of course, while under the springs pressure, the lever can be retained, for a slower ramp and lower pressure;
not programable, but consistently enough, with manual control;

yet I do not understand why the pump trying to reproduce the lever profile does not consider the inerent 0 bar pressure "zone", due to the slower cylinder chamber fill;

Strega is the "worst" case as its pump 10 ml/sec flow rate, will fill most of the chamber in over 5 secs; a dipper or a plumbed in machine has a much higher flowrate but still requires at least 2-3 secs for headspace fill...
for a Synesso initial infusion pressure of 3 bar with a 4 sec duration, the initial 3 sec of 0 bar pressure of a dipper does count; and in the Strega case, as I have an unavoidable 5 sec slow preinfusion at 0 bar, I cannot reproduce the Synesso profile!

not to mention the flowrate problem: now, for a 20g of grind, I have 40g in the cup, in more than 30s, plus10 (minimum) to 25s preinfusion (diferent stages), for a shot total time of 40-55 sec;
besides the initial 0 bar zone problem, I don't know how to reduce the shot duration to 23-35 sec, for a 50% brew ratio with 40-45g out! by holding the lever I would reduce the flow rate and the pressure too, out of the target profile;

radudanutco wrote:my Strega has all the usual mod's: a pressure gauge on the pump exit, a PID on the group heater, a switchable dimmer on the pump;

yet I do not understand why the pump trying to reproduce the lever profile does not consider the inerent 0 bar pressure "zone", due to the slower cylinder chamber fill;

Strega is the "worst" case as its pump 10 ml/sec flow rate, will fill most of the chamber in over 5 secs; a dipper or a plumbed in machine has a much higher flowrate but still requires at least 2-3 secs for headspace fill...
for a Synesso initial infusion pressure of 3 bar with a 4 sec duration, the initial 3 sec of 0 bar pressure of a dipper does count; and in the Strega case, as I have an unavoidable 5 sec slow preinfusion at 0 bar, I cannot reproduce the Synesso profile!

not to mention the flowrate problem: now, for a 20g of grind, I have 40g in the cup, in more than 30s, plus10 (minimum) to 25s preinfusion (diferent stages), for a shot total time of 40-55 sec;
I cannot reduce the shot duration to 23-35 sec, for a 50% brew ratio with 40-45g out!

All the usual mods huh?

The Strega must have been a special case. On my lever (water line pressure/feed) and many other dipper levers (boiler fed), the flow rate is typically unrestricted so you do get a huge rush of water when the lever is down fully (you can slowly lower the lever to reduce the flow rate but is less accurate or consistent). The chamber seems to be filled within the first 1-2 sec. The exceptions are the Faema or Bosco-dipper-style groups which have the 'semi-valve' in the group head (I said semi because the consensus was flow rate control wasn't the original intent of that valve)

I've always been curious about the Strega, why don't someone order the plumbed only Strega (Strega R) - then you have a 'classic' HX lever without a pump. PID the group head and then you'd almost get the best of levers.

Same problem here with the flow rate...easy to solve - 40g out in 19 sec. Sure taste terrible though (as I have tried, not to that extreme though).

Interesting paper, although it seems a bit subjective and a bit dated considering they were using Super Jolly and Major. The claimed 20% increase in TDS seems rather high as well.
I wonder if we get same benefit with newer grinder.

Good Read

Jason gives a demo of what can be done with the Slayer. May be a little Hollywood here but its fun watching.

http://www.vimeo.com/36724424

another_jim wrote:Thanks!

It confirms the basic pressure profiling result that the classic spring lever profile is "about right" when it comes to stable and forgiving espresso prep.

But to get nit-picky on the details: It's interesting to see them distinguishing the effect of small profile changes in a sequence of four shot segments. Each segment has three possibilities, so there are 81 different profiles (3**4). That comes to 6480 (81*80) possible paired blind comparisons if all possible variations are considered. This is an impossible experimental design, obviously. My guess is that the data are derived from doing blind tests for variations on each segment while holding the others at medium values (this reduces the number of blind comparisons to 12). But this assumes the contributions to the taste of each shot segment is independent of the others.

The independence assumption leads to very specific predictions. For instance, if I took two randomly selected shot profiles, I could look up the graphs and predict which of the two shots had more sugar, which one more acid, which one more viscosity, etc. Now, if I taught a panel to rate a pair of blind shots for more/less on each of these factors; would their results accord with the prediction? If one makes these claims, this kind of testing should bee done.

Ah yes, I've been stung by the should bee many times.

Fwiw- this configuration of temp and profile wasn't all that on my Vesuvius with doses at 18gm and 2x in the cup. That profile at 200°F and stretched to 35+ seconds is pretty much what I was using anyway and wonderful.

I realize my V is a completely different animal, we don't know the dose and ratio the LM folks and my taste could very well be different then the LM folks. Never mind water and beans...

From what I see on the Vesuvius forum most of the users enjoy low pressure slow shots. No one there has gone into the detail that the LM folks have in that paper.

Hopefully someone with a high tolerance, lots of beans and time will be able to test all this.

Thanks for posting it all!