Pressure Profiling Update 3

elusive espresso... theorize, philosophize!

Pressure Profiling Update 3

Postby gscace on Thu Mar 29, 2007 1:48 pm

Pressure Profiling Update 3

I think I'm homing in on some concrete information about pressure profiling that is worth blabbing on about, so here goes:

First thing is that there seems to be a practical maximum pressure value beyond which things go to hell in a handbasket tastebudswise. I found this out when I was experimenting with pressure profiles that included a high-pressure hump at the beginning of the extraction. Values for the hump were as high as 165 psi (11.3 bar). My thinking was that if sweetness was extracted early in the brewing process, then maybe I could emphasize it by increasing pressure to a high value early on, reducing to more conventional values later. The result was that I extracted crema that was markedly bitter. Bitterness was muted by reducing the magnitude of the hump. Bitterness was removed once the max pressure value was reduced to 9.5 bars at the coffee cake, which adds credence to the conventional 9-bar wisdom. I learned later that Jim Schulman has also observed this effect. I also successfully replicated the effect for Peter Lynagh, of Terroir Coffee, when he came down to visit.

Once I learned that there was a maximum practical brewing pressure, I began to think of pressure profiling in terms of the minimization of undesirable tastes, rather than in terms of super-extracting desired compounds. Taste tests with Nick Cho demonstrated to me that the sweet tastes and mouthfeel are developed early in the brew process, with dilution occurring later. Unfortunately, in the tests mit Cho (gesundheit!) extraction of bitter compounds also occurred during the dilution phase, meaning that a balance needed to be struck between dilution of the drink to a desired volume and introduction of negative taste components. Reducing the brewing pressure as brewing progresses seems to be beneficial in reducing bitter tastes extracted during the dilution phase. Tests with Nick pointed to accentuated sweetness in Counter Culture Toscana, which in retrospect was really a subtraction of bitter components added in the last third of the brew process.

The most successful general profile that I have come up with to date (I've now got an excel file with a bazillion profiles mapped out in it) is a pressure profile in which the pressure rapidly increases from some nominal start value to 9 bars at the group (elapsed time of 1 second from start to full pressure) with a short 9 bar soak, then ramps downward in a slow linear fashion (straight line degradation) to around 7 ½ bar, with a more rapid, second-order (curved downward) slope over the last few seconds to around 6 bar, arriving at 6 bar 30 seconds after initiation of the brew cycle. This general shape can be used with or without a pre-infusion step. The pre-infusion that I've been using is to soak the cake at around 2 " 3 bar for 3 seconds, then quickly ramping to maximum value with an exponentially increasing slope. Full pressure is attained 3 seconds after the end of the low-pressure soak. This combination produces liquid evenly over the bottom of the filter basket almost as soon as the pressure begins its rapid increase. Regardless of whether or not pre-infusion is used, I've been using a very similar profile toward the end of the brewing period. If pre-infusion is not used, I increase the time of the high-pressure soak by a few seconds.

It seems to me that the efficacy of preinfusion is coffee specific. There are three basic coffees that I've inflicted pressure profiling upon and with which I can comment. I've been drinking dry-processed Ethiopian SOs, and Ethiopian-based simple blends that have a lot of mouthfeel and body. My tests with Nick used Counterculture Toscano. I don't really know what is in it, and for the purposes of this discussion I don't think I really need to know. And last weekend, Peter Lynagh and I concentrated on a very lightly roasted Brazil. Here's a link to Terroir's information about the coffee:

http://info.terroircoffee.com/content/view/17/2/

For brewing temps, the Ethipian DP and Toscano seem to like around 201F. The SO Brazil was brewed at 195 F. The blends seem at first blush to benefit from preinfusion. I think that the soak and subsequent rapid pressure ramp may produce more mouthfeel, but I need to revisit this as I haven't been systematic enough, particularly in light of our results with the Brazil. We found that pre-infusion was a waste of extraction time when brewing the SO Brazil. Unlike the blends, the SO Brazil produced two predominate tastes with great clarity " nuts and sweetness reminiscent of dried figs. Both nuttiness and sweetness were enhanced when the pre-infusion step was removed. The clarity of the Brazil made differences between brewing at constant pressure and brewing with profiled pressure easy to discern. Bitter tastes were evident with constant-pressure brewing and demonstrably removed by profiling.

Recently folks have come up to me on the street, shoving their pudgy fingers in my puny chest, demanding to know that if pressure profiling meant deemphasizing the last portion of the brewing process, why not just stop brewing early? After I imagine breaking their finger with a deft marital arts-type motion, I counter with the argument that early brew termination is different. Compare two shots of the same volume, but with one brewed in the style of brewtus interruptus, and the other brewed to satisfying completion with pressure profiling. If one terminates early, for example at 18 secs in a 27 sec extraction, the volumetric flow rate during the 18 second period is much faster than the flow rate for an extraction taking place over the entire period. The extractions that we are observing with profiled pressure have more or less constant flow rate throughout the entire time period, which means that the volumetric flow rate is less by 50%, but over a longer time period. This changes the taste.

As I try different coffees and gain more experience I'm getting more confident that pressure is worth exploring as a brew parameter. There is still a lot to learn here, but the tests with Terroir indicate that variable pressure is useful when one is brewing clean SO espressos in which one or two tastes are showcased. I'm not sure which cart drives which horse when it comes to blends. I don't know if various widely used pre-infusion schemes were developed because they work with traditional blends, or if blends end up being developed to mask machine deficiencies. My cynical self thinks it's the latter. I have a lot more to learn about this, and it gets more difficult when I'm using coffees I've munged together. I don't feel like I'm a good enough roaster or blending dude to come up with confident conclusions, other than to go back with what I learned about the Brazil SO and see if I can make any hay with the stuff I usually drink. That means I'm not close to closure, which means that if you all don't behave, rather than dislocate your digits I'll spring Pressure Profiling Update 4 on you.
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Re: Pressure Profiling Update 3

Postby barry on Sat Mar 31, 2007 9:53 am

gscace wrote:I'm not sure which cart drives which horse when it comes to blends. I don't know if various widely used pre-infusion schemes were developed because they work with traditional blends, or if blends end up being developed to mask machine deficiencies. My cynical self thinks it's the latter.



i don't think blends are consciously developed to mask deficiencies, but, rather, they are developed with the available equipment and a good blend would, therefore, behave in a way to minimize the inherent flaws in the equipment.
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Postby geir oglend on Sat Mar 31, 2007 5:37 pm

Very interesting research on pump pressure profiling Greg. It brings back memories of my lever days, using lever machines w/ 1 or 2 springs in the piston assembly which would push the piston down at different pressures throughout the percolation curve, very reminiscent of what you are working on. Has anybody data logged the pressure curve on a lever machine accurately to see if it actually is flat or all over the place?
Waiting for update #4.
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Postby Mark Prince on Sat Mar 31, 2007 5:43 pm

I was reading Greg's post too, and couldn't help thinking about the scenario where a master Barista, working on a direct lever system (ie, not a spring lever) could finesse the pressure on the shot, based on decades of experience.

I'm not even sure if that barista ever existed though - IIRC, almost all the commercial lever espresso machines sold since Gaggia brought forth the Crema have been spring piston designs?

But hey, what's old could be new again.

Re: spring pressure curves - I'm no engineer, but I'd guess there's at least a subtle dip in the pressure as the spring expands in the piston. All the spring levers I've seen the guts of don't "bottom out" the spring (ie, it doesn't fully expand - when the lever is up, the spring is still exuding tension), but going from the max compressed state (lever down) to less compressed state (lever up), there's gotta be some kind of force drop in the spring's push.

Mark
PS - possible dream machine: programmable temperature curves, dual boiler design, but with adjustable spring piston levers. I asked Kees if he'd do a Speedster with a lever design several months back. No problem! Well, except for one niggly - I have to raise the money to fund the project.
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Postby Scott Rao on Mon Apr 02, 2007 8:17 am

mark-
according to wikipedia: "Springs that are only stretched or compressed slightly obey Hooke's law, which states the force with which the spring pushes back is linearly proportional to the distance from its equilibrium length."

meaning the spring's pressure decreases in a linear fashion during extraction. and you're right, the spring should not be fully expanded in the lever-up resting position. i imagine if it were the pressure toward the end of the shot would have dropped so low that there would be a pool of water on top of the grounds instead of the drier puck characteristic of lever extractions.

my guess is that the actual pressure change is not exactly linear, due to the decreasing resistance offered by the puck as it gets spent. this should lead to a slight acceleration in the spring's extension, and on a chart the pressure curve would have a slight downward slope. factors such as channeling could make the pressure curve vary slightly for any individual shot.

i would also assume if the pressure were measured with a puck which offered constant resistance (like in a scace thermofilter) the pressure change would be exactly linear.

p.s. i'd consider going in on financing the speedster lever project; i'd asked kees previously for a single-group lever machine and the speedster would be ideal.
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Postby Mark Prince on Mon Apr 02, 2007 3:25 pm

Hey Scott - thanks for the further info on springs.

I don't want to hijack Greg's thread at all here, but whenever talk about pressure profiling comes up, I think about piston lever machines. I think about things like direct lever systems (a la Pavoni's home models) where your arm is applying the pressure, and can choose to speed it up or slow it down. I think about spring piston levers and how maybe spring tension can be somehow controlled and / or adjusted, via some kind of gee-whiz computer control.

I think that the original illy, way back in 1935, maybe was on to something with hydraulically controlled pressure in espresso machines.

I know Andy has got his project going, and Greg's mind is much more suited to this kind of thing... so I want to throw this out there:

Is there current day, easily applied technology available for espresso machine manufacturers to more precisely control pressure, and more importantly, give the end user (ie, Barista) the ability to control it second by second in the shot pull?

Is there a way to more easily control springs in a lever system?

Is the rotary pump really the most ideal solution to pushing water through a bed of coffee?

I don't need any convincing that pressure profiling can result in a better shot. I've seen the advantages of the .6 gicleurs, how e61 groups can pull different shots than other machines, and how to this day the most sublime, standout shot of espresso I've ever had came from a piston lever machine (I think there may also be something in what Jim Schulman wrote elsewhere - the "whole block of water" theory vs. streaming water to a puck)... all tinker with the water pressure as it hits the puck, or do something different, and you see and taste it in the extractions.

For me, I'm more curious in how we can achieve this, instead of the question "is it better". What are the technical limitations and possibilities? Is going back into the past, and using (I assume easily) computer-controlled hydraulics the answer?

Mark
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Postby Jim Schulman on Mon Apr 02, 2007 6:04 pm

MarkP wrote:
Is there current day, easily applied technology available for espresso machine manufacturers to more precisely control pressure, and more importantly, give the end user (ie, Barista) the ability to control it second by second in the shot pull?


It's easy enough to put a speed control on a motor and have the barista manually twiddle the dial while watching a pressure guage -- I did it a few years back with a vibe pump. I got some extra smoothnmess from the shots by dropping the pressure at the end, but it didn;t compare to the lever profiles.

More complicated, but still straightforward, would be to modify current lever groups to have the piston driven by a motor via a worm gear.

However, when I did this, I found I preferred to watch the shot than twiddle a dial and watch a pressure guage -- especially, since I'm not Harold Lloyd, if I was trying to steam milk at the same time :wink:
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Postby gscace on Mon Apr 02, 2007 6:16 pm

MarkP wrote:Hey Scott - thanks for the further info on springs.

I don't want to hijack Greg's thread at all here, but whenever talk about pressure profiling comes up, I think about piston lever machines. I think about things like direct lever systems (a la Pavoni's home models) where your arm is applying the pressure, and can choose to speed it up or slow it down. I think about spring piston levers and how maybe spring tension can be somehow controlled and / or adjusted, via some kind of gee-whiz computer control.

I think that the original illy, way back in 1935, maybe was on to something with hydraulically controlled pressure in espresso machines.

I know Andy has got his project going, and Greg's mind is much more suited to this kind of thing... so I want to throw this out there:

Is there current day, easily applied technology available for espresso machine manufacturers to more precisely control pressure, and more importantly, give the end user (ie, Barista) the ability to control it second by second in the shot pull?

Is there a way to more easily control springs in a lever system?

Is the rotary pump really the most ideal solution to pushing water through a bed of coffee?

I don't need any convincing that pressure profiling can result in a better shot. I've seen the advantages of the .6 gicleurs, how e61 groups can pull different shots than other machines, and how to this day the most sublime, standout shot of espresso I've ever had came from a piston lever machine (I think there may also be something in what Jim Schulman wrote elsewhere - the "whole block of water" theory vs. streaming water to a puck)... all tinker with the water pressure as it hits the puck, or do something different, and you see and taste it in the extractions.

For me, I'm more curious in how we can achieve this, instead of the question "is it better". What are the technical limitations and possibilities? Is going back into the past, and using (I assume easily) computer-controlled hydraulics the answer?

Mark


The technology exists to precisely control pressure and to program a pressure profile into the espresso machine. I think that one could also tweak it on the fly if one wanted to, although I think you'd get better results by programming the profile and sorting out the grind to suit. Most folks who are at this point in their craft can pull similar shots back to back. The system that I built is made entirely of commercial stuff. The pump is a Fluid-o-Tech TMFR pump, which is a rotary vane pump that is magnetically coupled to a variable speed drive. The pump has advantages over a regular rotary pump in that there is no shaft seal to fail, so lifetime is extended several times. Also the power required to drive it is waay less. The thing is waay more economical to run than an AC motor attached to a pump. Cost of the pump is not that horrible. The electronics and pressure transducer associated with the system bring the cost up to where it ain't gonna be in your casual shop serving swill. But the system is robust enough to survive commercial duty in any environment, and if a manufacturer wanted to incorporate it into their machine, they could do so pretty economically.

-
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Postby Andy Schecter on Mon Apr 02, 2007 8:14 pm

MarkP wrote:Is there current day, easily applied technology available for espresso machine manufacturers to more precisely control pressure, and more importantly, give the end user (ie, Barista) the ability to control it second by second in the shot pull?


Quite a few folks are working on it. Among the problems remain:
1. "easily applied," yes, but "inexpensive," so far, no.
2. the "MMI" (man-machine interface, ie, the means to alter the pressure profile) is rather user-unfriendly.
3. multi-group machines require multiple profiling pumps, eg, a three group machine necessitates nearly three times the already substantial cost of a one group installation.

Hopefully these problems will yield to vigorous R&D.

Meanwhile, if you can live with the unalterable, decreasing pressure profile that the spring lever machines deliver, they remain a simple, reliable and remarkably elegant solution.

Michael Teahan has proposed a machine that allowed manual control over both the brew water temperature and the extraction pressure during the shot. His concept would use control levers to affect changes to each as the shot unfolded. This would make pulling a shot sort of like operating the throttles on a twin-engine airplane.

A system like this would seem to meet your desire for direct manual control, Mark. You could "fly" each shot in for a smooth landing. :)
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Postby Mark Prince on Mon Apr 02, 2007 9:07 pm

AndyS wrote:Michael Teahan has proposed a machine that allowed manual control over both the brew water temperature and the extraction pressure during the shot. His concept would use control levers to affect changes to each as the shot unfolded. This would make pulling a shot sort of like operating the throttles on a twin-engine airplane.

A system like this would seem to meet your desire for direct manual control, Mark. You could "fly" each shot in for a smooth landing. :)


How is that system be any different from say, the current direct lever design of the La Pavoni Europicola and Professional (putting aside for a moment the temperature controls obviously missing from those consumer machines)?

And a further thought:

While most likely not an ideal, high volume commercial machine, a possible dream machine setup for someone who wants a lifetime of fine tuning espresso directly, could be a temperature profile controlled, dual boiler Speedster style machine with a direct lever system. The human side of the equation can't do much about controlling temperatures of the brewing water, so let a computer, PID / whatever do that magic. But the human can, esp. with a lot of practice, control the exerted pressure on the bed of coffee.

Problem is, I don't think this dream machine could be built with today's available parts - the Pavoni's grouphead is imo too small and also relies on a heatsink design to keep it hot (and the brewing water that enters the cavity when you lift the lever up)... sticking that piston grouphead on a dual boiler design would screw up the engineering I'm guessing. And I don't know of any other direct-lever designs being made today (there's several spring levers out there, but afaik only one direct-lever system) - anyone know of any besides Pavoni's group?

To get this dream machine, a new grouphead / piston would have to be designed - a new design that allows maybe for a saturated grouphead, or the entire brew boiler sitting in the grouphead / lever housing, plus a better puck size than 49mm or 51mm could lead to some really interesting results. Dalla Corte has a "grouphead is the boiler" design, and so do Synesso, sort of, but neither seem to be conducive to modification to a direct lever pressure system.

There doesn't seem to be much interest in the industry in going back to levers. I've talked to a few companies about it (La Marzocco, Rancilio, Elektra), and with Kees about what's out there (not a hella lot - he's using, IIRC, the Gaggia spring piston 60ml commercial lever on his lever Mirage Idrocompresso - one of the most beautiful machines made today), and I think that's a shame - levers not only exude the "romance" part of espresso, but I also think they have the potential to bring more control and interesting effects to the beverage.

So unless the big (and not so big) manufacturers start looking at levers in a new way, we're stuck with a few companies (Gaggia, Pavoni, Nuova Simonelli, a few others) and a handful of available lever designs based on 50 year old specs. Still, I wouldn't mind interfacing for a dozen years with a dual boiler, preheating system, temperature controlled Speedster with that Gaggia spring piston lever design, with maybe a set of easily swappable springs included with the machine to provide a choice of pressures, like maybe .1 BAR up or down.

Or even better, and more frustrating - a direct lever system that will force me to get better at making espresso, or suffer trying. Give me good temperature controls (something the Pavonis don't have) - I'll create my own pressure profile, damnit; ;)

Mark
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Postby barry on Mon Apr 02, 2007 9:16 pm

AndyS wrote:Michael Teahan has proposed a machine that allowed manual control over both the brew water temperature and the extraction pressure during the shot. His concept would use control levers to affect changes to each as the shot unfolded. This would make pulling a shot sort of like operating the throttles on a twin-engine airplane.



i want a speed brake on my espresso machine! :D



--barry "dude, look at all the levers!"
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Postby barry on Mon Apr 02, 2007 9:19 pm

MarkP wrote:But the human can, esp. with a lot of practice, control the exerted pressure on the bed of coffee.


especially with a big honkin' pressure gauge to watch whilst one is espressing the coffee.
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Postby Mike Paras on Tue Apr 03, 2007 5:33 am

MarkP wrote:...sticking that piston grouphead on a dual boiler design would screw up the engineering I'm guessing.


Couldn't someone could just make a separate manual piston pump that could be swapped in to replace the rotary pump of virtually any normal machine- like a prehistoric Schectermatic?
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Postby barry on Tue Apr 03, 2007 9:42 am

mikep wrote:Couldn't someone could just make a separate manual piston pump that could be swapped in to replace the rotary pump of virtually any normal machine- like a prehistoric Schectermatic?



hhmmmm... interesting idea.
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Postby Kevin Cuddeback on Tue Apr 03, 2007 7:01 pm

This patent seems to be coming at it from a different direction: A mechanism on the bottom of the portafilter to maintain back-pressure during the shot to eliminate channeling?

Which of the following would best characterize that patent?
a. On-topic
b. Slightly off-topic
c. Not on topic
d. Technically irrelevant

I'll defer to the Pro-Alties for an explanation of how it may relate.
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Postby barry on Tue Apr 03, 2007 8:04 pm

interesting, kevin, but it seems to make the same error as the consumer crema-enhancing portafilters: "all good shots have crema" is not the same as "all shots with crema are good". the operational description makes this clear: "...to emulsify and assume the enhanced creamy appearance which... gives quality to the drink."

my take is this device is an automatic version of the old spidem/rancilio two-position portafilters, where one would start the shot with the portafilter valve closed, and wait until the pump strained against the restriction before opening the valve to allow the espresso to flow into the brewing vessel, through an emulsifying valve.

i don't know if this makes any improvement in what would otherwise have been a marginal shot, other than to improve the appearance of said shot ("give quality to the drink").
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Postby gscace on Wed Apr 04, 2007 7:06 am

MarkP wrote:
Problem is, I don't think this dream machine could be built with today's available parts - the Pavoni's grouphead is imo too small and also relies on a heatsink design to keep it hot (and the brewing water that enters the cavity when you lift the lever up)... sticking that piston grouphead on a dual boiler design would screw up the engineering I'm guessing. And I don't know of any other direct-lever designs being made today (there's several spring levers out there, but afaik only one direct-lever system) - anyone know of any besides Pavoni's group?

To get this dream machine, a new grouphead / piston would have to be designed - a new design that allows maybe for a saturated grouphead, or the entire brew boiler sitting in the grouphead / lever housing, plus a better puck size than 49mm or 51mm could lead to some really interesting results. Dalla Corte has a "grouphead is the boiler" design, and so do Synesso, sort of, but neither seem to be conducive to modification to a direct lever pressure system.



Mark


Well I don't see what is limiting anyone from putting the lever upstream of the brew boiler on a double boiler machine, or hx on a hx machine if it's a lever that you want. Think of the lever-actuated piston as replacing the pump and you can pretty much put the damn thing anywhere. Also, the mechanism ain't unique to coffee. It's really simple, and anyone with the skills to build machinery could build a lever actuated piston.

One thing that I want to mention and that is getting incorrectly surmised in the discussions here, Home-barista, and alt.coffee is that it hasn't been demonstrated that the lever profile is correct. My opinion right now is that the lever profile is a happy accident that seems like it is a bit more correct than constant pressure. Spring-actuated lever machine pressure profiles drop more or less linearly (straight line) from a maximum pressure that is at the very beginning of the extraction (not counting any soaking period). The reason for this is that the spring is relaxing as it pushes the piston down. Force exerted by a spring is F = K*X, where K is the spring constant, defined as force per unit length (pounds per inch, Newtons per meter)and X is the compression displacement of the spring from its fully relaxed condition (free length). So the pressure exerted on the water by the spring-loaded piston is dependent on the position of the piston in the cylinder, and thus it's also related to the amount of water that has been forced into and through the coffee. As we know, the flow rate through a coffee cake is variable. Lots of water is absorbed by the cake in the first part of the extraction, so the piston travels pretty quickly unless the cake has been well soaked during the lever cocking phase (or whatever ya wanna call it). Things get different once coffee is pushed out the cake by water entering from the top because the viscosity gets thinner as the extraction progresses. Under constant pressure, the flow rate increases, but under lever profile conditions, this may not be so pronounced. If the piston ends up travelling down the cylinder at a constant speed, then the pressure profile will be linear. If the piston picks up speed due to increased flow rate, then the profile will be curved, with the rate of pressure drop increasing toward the end of the extraction. I suppose the deviation from linear is dependent on the type of coffee used, the age and degree of roast, the fineness of grind, volume of dose and the degree of tamping.

Electronic pressure profiling allows one to deviate from near linear profiles. From what I've been able to see so far there's some benefit to constant high pressure for the first few seconds, a linear decline, then a non-linear and more rapid pressure decline in the last 6 or so seconds. This sort of profile can't be easily achieved with a spring-loaded lever, but could be achieved with a lever-actuated piston operated completely by hand.

I'm imagining that educating oneself to run a lever completely by hand is gonna take a good bit of time, although I could see it as being rewarding in a way. But I bet you can do the same thing electronically and get more consistent results. This would be key if one's intent was to see these profiles getting used in the commercial world.

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Postby jakethecoffeelover on Tue May 01, 2007 12:57 pm

gscace: Is it possible that the increased sweetness (or decreased bitterness) you observed with the decreasing pressure profile is due to minimization of the physical extraction of bitter insolubles, while increasing the concentration for the solubles (saccharides, etc.) due to the decreased flow rate? Slower movement of the water through the puck and decreased compression on the puck would probably prevent the insoluble particles from snaking their way down through the mesh of coffee and into the cup. Maybe it's about time I got in on this pressure-geekery... :lol: When I was designing an espresso machine I looked quite far into the possibility of a pressure "throttle" on the exterior of the machine.
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Postby gscace on Tue May 01, 2007 1:44 pm

jakethecoffeelover wrote:gscace: Is it possible that the increased sweetness (or decreased bitterness) you observed with the decreasing pressure profile is due to minimization of the physical extraction of bitter insolubles, while increasing the concentration for the solubles (saccharides, etc.) due to the decreased flow rate? Slower movement of the water through the puck and decreased compression on the puck would probably prevent the insoluble particles from snaking their way down through the mesh of coffee and into the cup. Maybe it's about time I got in on this pressure-geekery... :lol: When I was designing an espresso machine I looked quite far into the possibility of a pressure "throttle" on the exterior of the machine.


My answer is I dunno. I'm pretty ignorant about what gets extracted at what temperature and pressure. It's a question for coffee chemist types. Maybe I'll get lucky and run into one or two this week at SCAA.

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Postby Lennoncs on Wed May 02, 2007 7:18 pm

I rigged up a fairly strange system for the E61 occupying otherwise useful space in the kitchen.

I controlled the pressure of my system based on the position of the lever on the group, full up is max(~9.2 bar), detent is set at a pre-infusion pressure and full down is off/vent.
it required a slight re-curve of the cam in the lever and the addition of a Detent plate to allow repeatable lever positions when I was not of the mind to fidget.

Since my pump is capable of working with both pressure and volume, I tried using the same setup as a volumetric control...bad idea, although I capped the maximum pressure at 9.2 bar, the system proved to be very difficult to get my head around at the time...I have not revisited the idea since.

I agree with Greg 100% that adoption of pressure control in the commercial setting is very important. our stumbling block is going to be user interface; programming a fuji controller is not a fun task and doesn't lead to a environment experimentation on the part of the barista, same with temperature profiling.
as for pressure profiling, a user interface that allows the operator to quickly specify aspects of the profile in a graphical, easy to comprehend format is going to be key.

just a few minor ramblings from a tired mind....

cheers,
Sean



P.S.
Greg, you should have taken a closer look at the setup in Charlotte, the interface was a touch-screen to draw the profile.
Lino and I just about trashed the hotel room the previous night tuning it. (it is still sitting in the transport case :( )
Sean Lennon
Davisburg mi.
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Postby Goatherd on Tue May 08, 2007 5:04 pm

I assume a few folks got to play with the concept Linea with paddle groups at the SCAA show. You could control preinfusion and the brew pressure with the paddles and watch the pressure changes in real time on the gauge. It was tha shit! I pulled some shots using ideas from this thread and got some interesting results. Also pulled some shots trying to mimic the profile from a lever machine and got similar results. Unfortunatly I only got about 6 shots pulled until I was feeling the pressure to move on. The ESI folks said that when this design comes out (a few years maybe) you will be able to retro-fit Lineas and GB/5s to use the paddles. FYI you can only control the pressure of one group at a time.
Any other feedback on this machine...MarkP, AndyS, GregS...did ya'll check this thing out?
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Postby gscace on Fri May 11, 2007 6:30 am

Goatherd wrote:I assume a few folks got to play with the concept Linea with paddle groups at the SCAA show. You could control preinfusion and the brew pressure with the paddles and watch the pressure changes in real time on the gauge. It was tha shit! I pulled some shots using ideas from this thread and got some interesting results. Also pulled some shots trying to mimic the profile from a lever machine and got similar results. Unfortunatly I only got about 6 shots pulled until I was feeling the pressure to move on. The ESI folks said that when this design comes out (a few years maybe) you will be able to retro-fit Lineas and GB/5s to use the paddles. FYI you can only control the pressure of one group at a time.
Any other feedback on this machine...MarkP, AndyS, GregS...did ya'll check this thing out?


Now that's cool! I saw it, and like an idiot I didn't ask Bill what the deal was with it. Duhhhh. Damn!

-Greg
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Postby Goatherd on Fri May 11, 2007 7:53 am

Yeah Greg,
I've kinda been suprised that folks haven't been talking about it more. The dude I talked to at the booth said I was the first person to say, "Holy shit! I can pull shots to mimic a lever machine with this thing!" (could that possibly be true as of Sunday afternoon?)
Honestly, I find it hard to believe that no one else saw/played with this thing... anyone?...anyone?
I mean, we'll (in the future) be able to retro-fit GB/5s with the paddles! Am I the only one freaking out here!?!
Is this not as great as it seems? Am I missing something?
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Postby Isaac Gonzalez on Sat May 12, 2007 2:08 pm

I think the easiest(and cheapest) way to vary the pump pressure on an espresso machine is to take the motor out from under the counter(on Marzoccos), set it on the counter or on top, and adjust the pump pressure using the set screw on the pump head. Now when you pull a shot turn it clockwise for more pressure and counter clockwise for less pressure. Too high a pump pressure may cause leaky gaskets and the lowest pressure you will get is the incoming water pressure from that tasty large pipe under the street.

It is free, you simply need a way to keep your screwdriver in place throughout the day.

cheers
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Postby Alistair Durie on Sat May 12, 2007 2:32 pm

stuntgoat wrote:It is free, you simply need a way to keep your screwdriver in place throughout the day.


vice grips.
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