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Thread: Heat: Understanding an Age-Old Problem in Espresso...

  1. #1
    Mal Dimal's Avatar
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    Heat: Understanding an Age-Old Problem in Espresso...

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Another article I read recently and thought might be of interest to other CSers...
    https://dailycoffeenews.com/2019/05/...m-in-espresso/

    Mal.
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    Good one Mal.

    Indirectly shows why a mixing valve setup (like the DE1) is a better use of technology than either a boiler or a thermocoil - as long as you have enough sensors embedded in the grouphead to know what is happening in real time.

    TampIt
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    Maybe the Bezera electric heated group solves the problem assuming they can regulate it properly (don't have one so I'm not sure)

    Good read

    Cheers

  4. #4
    Senior Member Yelta's Avatar
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    Interesting read Mal.

    I wonder if precise temperature stability is really a problem for the average home barista, seems most quality machines manage the problem quite well without indulging in overly complicated electronic gymnastics.

    There will always be the geek who want absolute perfection and claims to be able to detect minute fluctuations in temperature, in practice I suspect most will be very well served by the better quality machines currently available at prices that you don't need to take out a second mortgage to buy.

    In most cases its the skill and understanding of the operator that ultimately determines the quality of whats in the cup, all of the electronic wizardry in the world wont overcome the faults produced by cheap low quality coffee and poor technique.

    We have a friend who has almost every bit of the latest kitchen wizardry known to man, still cant cook worth a damn, to a large degree, its not the gear you've got but how you use it.
    Last edited by Yelta; 4 Weeks Ago at 10:39 AM.
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    Ive recently put a PID onto my silvia (yeah I know so has everyone else). I ended up building it myself with a 7100XMT off e bay.

    I'm astounded at the improvement in shot result I am getting as well as the consistency. In terms of this upgrade the heat control is very noticeable over thermostat control.

  6. #6
    Senior Member CafeLotta's Avatar
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    I found it very interesting to see how my E61 grouphead temp varies under different conditions after having used a grouphead thermometer for a while now. It's easy for anyone to taste a sour or bitter shot due to too low or high brew temps but controlling the temp band in between can offer some interesting results.

    Quote Originally Posted by SanderP View Post
    Maybe the Bezera electric heated group solves the problem assuming they can regulate it properly (don't have one so I'm not sure)
    Seems quite funny that the cheap "appliance" Breville BES920 has a PID controlled group heater whereas Bezzera still use a thermostat. The BES920 also has brew-water pumped through the steam boiler to pre-heat it similar to an Izzo Alex Duetto which is one of 2 Italian machines that do this. Maybe time for a number of the big Italian manufacturers to join the 21st century?
    Last edited by CafeLotta; 4 Weeks Ago at 11:02 AM.
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    Senior Member Yelta's Avatar
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    Quote Originally Posted by CafeLotta View Post
    Seems quite funny that the cheap "appliance" Breville BES920 has a PID controlled group heater whereas Bezzera still use a thermostat. The BES920 also has brew-water pumped through the steam boiler to pre-heat it similar to an Izzo Alex Duetto which is one of 2 Italian machines that do this. Maybe time for a number of the big Italian manufacturers to join the 21st century?
    Morning CafeLotta, perhaps its a case of if it ain't broke don't fix it.

    I'm struggling to understand what benefits added complexity will afford me, my E61 machine is certainly stable enough for my requirements, on the other hand there is always the possibility that my taste is easily satisfied and I simply don't pick up on the variations that others perceive, however I don't think this is the case.

    There seems to be the belief that if a machine doesn't have all of the latest bells and whistles along with unlimited variable parameters then its simply not up to the task of producing a decent espresso, I've had shots made on all manner of modern wonders, some very good, a lot less than average, however I still believe my antique E61 is capable of blowing most of them out of the water, perhaps I'm living in a fools paradise.

    As a matter of interest what temperature variations do you see on your machine during a session?

    Another point I've wondered about is depth of roast, I'm very much into Italian style espresso (dark roast) do temp variations affect lighter roasts more than dark, given that it seems the average Australian palate seems to prefer lighter roasted beans, there certainly are marked differences in what is offered in Italy and our Aussie preferences.
    Einstein complexity.jpg
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    Mal Dimal's Avatar
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    Not a matter of "all the bells and whistles" Yelta...
    PID Control, for example, has been used in commercial and industrial applications and then consumer devices for far longer than I've been alive, as well as being very simple and reliable. The digital age has just allowed this control system to be miniaturised and become even more reliable and simple to operate successfully.

    The same can be said for a wide range of other forms of systems control...

    Mal.

  9. #9
    Senior Member Yelta's Avatar
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    Quote Originally Posted by Dimal View Post
    Not a matter of "all the bells and whistles" Yelta...
    PID Control, for example, has been used in commercial and industrial applications and then consumer devices for far longer than I've been alive, as well as being very simple and reliable. The digital age has just allowed this control system to be miniaturised and become even more reliable and simple to operate successfully.

    The same can be said for a wide range of other forms of systems control...

    Mal.
    G'Day Mal, not specifically referring to PID controllers, my belief is that adding electronic layers of complexity unnecessarily is simply change for the sake of change with no added benefit, other than perhaps for repair shops.

    Couple this with allowing users almost unlimited control over variables is a recipe for total confusion, the number of new users who have difficulty coming to terms with a basic espresso machine underscores this.

    I've seen it in an industrial setting where we had to set electronic controllers then lock the box to prevent operators messing with the settings and bringing production to a standstill.
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    Senior Member level3ninja's Avatar
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    Quote Originally Posted by Yelta View Post
    I've seen it in an industrial setting where we had to set electronic controllers then lock the box to prevent operators messing with the settings and bringing production to a standstill.
    There's idiot proof, and then there's operator resistant. I am yet to meet operator proof. We often try to guess how long it will be until an operator breaks something or a loader driver manages to run into something when we install new systems for a certain customer.
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    Quote Originally Posted by level3ninja View Post
    There's idiot proof, and then there's operator resistant. I am yet to meet operator proof. We often try to guess how long it will be until an operator breaks something or a loader driver manages to run into something when we install new systems for a certain customer.
    Its horses for courses really. At the end of the day were just talking about home coffee machines here. I would suggest that more than 50% of people that buy a prosumer machine just end up using it in the most simple way, have never even heard of a coffee forum and have no interest in that changing. So simple, tried and tested e61 technology is fine for them. For people that are starting to explore all the possible sensory experiences that coffee can offer then a traditional and basic e61 HX machine will be limiting. Variables that can be changed and set by the owner will greatly improve that experience.
    Then at the other end of the spectrum youve got industries like the one I work in where every system thats in place that operators dont actually need to manipulate or control to do their job MUST be locked out, protected, or sealed. Its generally a regulatory and sometimes legal requirement.
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    Senior Member CafeLotta's Avatar
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    Quote Originally Posted by Yelta View Post
    Morning CafeLotta, perhaps its a case of if it ain't broke don't fix it.
    Hi Yelta. It's just a case of evolution I suppose. Starting with the many Silvia owners who added a PID controller after getting sick and tired of having to temperature surf to avoid burnt, bitter coffee or at the very least, the lack of consistency. Then there's those with badly set-up Hx machines who don't get the results they expected out of the box. Some learn to work around this by using flushing routines (in effect temp surfing again) but others don't and just have a bad coffee experience.

    Quote Originally Posted by Yelta View Post
    I'm struggling to understand what benefits added complexity will afford me, my E61 machine is certainly stable enough for my requirements, on the other hand there is always the possibility that my taste is easily satisfied and I simply don't pick up on the variations that others perceive, however I don't think this is the case.
    Sounds like you're lucky enough to have a temp stable Hx machine which is setup correctly. You no doubt also have the experience to get the best out of it. Reading across a couple of different forums there seem to be many Hx machine owners struggling to get the results they expected after investing lots of dollars in equipment, with some brands fairing better than others. The hobbyist coffee enthusiast will seek information, educate themselves and learn the skills to work around shortcomings of certain machine designs or setup. This isn't the expectation of the average person after investing big in good equipment for better coffee brews at home. As I've been saying recently, my observation is that the lack of accurate brew temp control on certain machines or machine designs seems to be the common factor in many bad coffee experiences. Badly designed or badly setup E61 Thermosyphon circuits exacerbate this.

    Quote Originally Posted by Yelta View Post
    There seems to be the belief that if a machine doesn't have all of the latest bells and whistles along with unlimited variable parameters then its simply not up to the task of producing a decent espresso, I've had shots made on all manner of modern wonders, some very good, a lot less than average, however I still believe my antique E61 is capable of blowing most of them out of the water, perhaps I'm living in a fools paradise.
    My thoughts on the subject lately have been based on trying to see it from the point of view of someone starting out. Regardless of what machine you buy, once you start grinding into a portafilter to brew, the onus is on you to at least understand how to find the correct grind setting, correct dosing and understand tamping basics. Many seem to struggle with this initially but usually get to a point where they're not over/under dosing, don't have channeling and achieve a desired flow rate when brewing. The attention of a number of people then turns to "why doesn't my coffee taste as good as it should." Assuming that good quality fresh roasted beans are being used and they've played with Grind, Dose and Tamp, the answer usually lies with incorrect brew temp in my opinion (assuming there are no machine faults). If this variable can be easily and accurately controlled, the average user would have a better early coffee experience in my opinion. Yes, there is varying degrees of additional design complexity that accompanies this function and cost and reliability can come into play.

    Quote Originally Posted by Yelta View Post
    As a matter of interest what temperature variations do you see on your machine during a session?
    My older VBM E61 single boiler (thermostat controlled) can show quite a variation depending on warm-up duration and how long it's been sitting idle once past the initial warm-up. After trying various flushing routines to try to speed warm-up, I did have to concede that the widely quoted E61 30 min warm-up does yield the best results. Being an old machine that I've never had apart, I'm sure there's probably a little scale build up and the heating element and capillary thermostat likely aren't at there optimum.

    To answer your question, on good days and sticking to a strict routine, I can keep it inside 1 deg C variation (on the grouphead thermometer) for the 25-30 sec brew. When rushing or distracted and especially with too short a warm-up, 3-4 deg C variation can slip in and I usually chuck those.

    For what I'm chasing and without PID at the moment (still) it's a bit of a juggling act to get the result I'm after. I also think the thermosyphon in my machine is running a bit cold as I need to heat the grouphead with careful flushing before brewing to keep the temp variation down. The grouphead thermometer is essential for me to do this. It was a frustrating time picking up the patterns in temp behavior on my machine and the flush pattern required to tighten the brew temp variation. It's very fickle. I don't know if it's typical for this machine but user input plays a big part. Drinkable brews aren't difficult to achieve but getting them at my preferred end of the temp scale is where the extra effort is required on my part. This is where the PID will hopefully improve things if I can let myself take the machine out of service long enough to do it. I've tried different thermostat settings but settled on the best compromise for my requirements. Like the Silvia without PID, I'm temp surfing to get the results I'm chasing. Without the E61 Grouphead thermometer, I couldn't do this.
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    Senior Member Yelta's Avatar
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    Thanks for the comprehensive and well thought out reply CafeLotta, very interesting/informative.
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    Quote Originally Posted by Yelta View Post
    G'Day Mal, not specifically referring to PID controllers
    PID Control, for example, has been used
    Neither was I mate, just used as an example given that this is an aspect that is often discussed in association with espresso machines...

    Mal.
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    Gday all

    FWIW, I "just" wanted to equal my manual lever Electra in terms of flavour without having to go through all those arcane rituals to get there. Also, doing three cuppas in a row would be a nice change.

    The only machine I know of that can do that is the Decent DE1 - you can actually tinker your way there (and even beat the Electra after a bit of experience). Its other advantage - once set up, just press "start" and await a stunning pour. It is also the only machine I know of that actually satisfies the tinkerers and teh "which button do I press" brigade.

    Oh, and yeah - dark roasts are so much easier to control than mediums, and light roasts are a magnitude harder again. My 2 group La Pav / SB 6910 / SB 7000's are all capable of delivering great dark roasts into a cuppa. The La Pav struggles with mediums and the SBs struggle with light roasts.

    TampIt
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    There are at least three different temperature concepts that need to be distinguished: stability during a shot, repeatability across multiple shots and adjustability.

    Before any of the above concepts are meaningful, your barista technique needs to be good enough. If you can't pull five shots in a row that are within a few seconds, a few grams and are pretty much indistinguishable in taste, focus on getting that down pat before spending money or getting FOMO. Assuming you can do that - it's much, much more difficult than most people think - read on.

    Stability during a shot means how flat does the temperature stay during a shot. A lot of the early writing on temperature stability comes from people experimenting on early LMs because they achieve temp stability through the saturated group, basically an extension of the boiler. That massive mass of water delivers fairly consistent temps at the top of the puck across a shot and was a technologically simple and easy way to control temperature. I have never read or seen anything that suggests that flat temperature across a shot is the best result. Rather, having a flat temperature profile was, at least at the time, an easy way to measure and control temperature for repeatability. It may be that a rising or declining temperature profile across a shot is best. There are some machines now that can do that. So watch this space: I don't think anyone knows. I think that stability during a shot is basically a legacy of what was possible at particular points in time. An e61 HX might have a temperature hump and slump. That doesn't mean it will taste worse.

    Repeatability across shots, on the other hand, is pretty important. It's clearly important in an espresso bar if it means that your shots taste different as your machine warms up. This was a lot of the impetus behind PIDding LMs. At home, it's probably less important, since you are unlikely to make a lot of shots back to back. If you're making one PF's worth of shots, then leaving the machine and coming back, this probably isn't an issue. If you're making a bunch of shots back to back, you might find they taste different. If you walk up to a machine and pull shots with perfect puck preparation and they taste different, then you have a problem. CafeLotta's post above gives a good rundown on e61 warming. (FWIW, I made a little insulating hood to sit over my e61 group for faster warmup and, hopefully, to reduce variability between shots, but I never got around to testing that second bit.)

    Adjustability is only really relevant once you have repeatability across shots. Adjustability isn't really all that necessary to brew great coffee. I have an e61 HX at the office and a very adjustable machine at home and I enjoy coffee at both places. What happens is this: if you can't fiddle with things easily on your machine, you will optimise everything else to perform best on your machine and you will probably get good results if your machine can deliver repeatability across shots and generally doesn't suck. You will probably find that there is one particular roaster that you think is god's gift to coffee and that you disagree violently with someone else on the internet who likes some other roaster. You will probably find that if you take your coffee and extract it on their machine, you hate it. If you can fiddle with settings easily on your machine, then what actually happens is this: you fiddle with too many things at once and make your coffee taste bad without being able to pinpoint why. Occasionally, you will get great coffee. But if you can fiddle with settings easily on your machine, then the practical difference should be that once you have enough experience you can adjust your machine to get good results out of a wider array of coffee.

    So I don't think that anyone needs to despair that they will never get good results if they don't have a temperature adjustable machine. Equally, I don't think it's fair to run around saying the emperor has no clothes.
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    Very interesting read. Thanks for sharing

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    Mal Dimal's Avatar
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    A well thought out and practical response Luca.
    Thoroughly agree with your outlook...

    Mal.

  19. #19
    Senior Member Yelta's Avatar
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    Quote Originally Posted by luca View Post
    There are at least three different temperature concepts that need to be distinguished: stability during a shot, repeatability across multiple shots and adjustability.

    Before any of the above concepts are meaningful, your barista technique needs to be good enough. If you can't pull five shots in a row that are within a few seconds, a few grams and are pretty much indistinguishable in taste, focus on getting that down pat before spending money or getting FOMO. Assuming you can do that - it's much, much more difficult than most people think - read on.

    Stability during a shot means how flat does the temperature stay during a shot. A lot of the early writing on temperature stability comes from people experimenting on early LMs because they achieve temp stability through the saturated group, basically an extension of the boiler. That massive mass of water delivers fairly consistent temps at the top of the puck across a shot and was a technologically simple and easy way to control temperature. I have never read or seen anything that suggests that flat temperature across a shot is the best result. Rather, having a flat temperature profile was, at least at the time, an easy way to measure and control temperature for repeatability. It may be that a rising or declining temperature profile across a shot is best. There are some machines now that can do that. So watch this space: I don't think anyone knows. I think that stability during a shot is basically a legacy of what was possible at particular points in time. An e61 HX might have a temperature hump and slump. That doesn't mean it will taste worse.

    Repeatability across shots, on the other hand, is pretty important. It's clearly important in an espresso bar if it means that your shots taste different as your machine warms up. This was a lot of the impetus behind PIDding LMs. At home, it's probably less important, since you are unlikely to make a lot of shots back to back. If you're making one PF's worth of shots, then leaving the machine and coming back, this probably isn't an issue. If you're making a bunch of shots back to back, you might find they taste different. If you walk up to a machine and pull shots with perfect puck preparation and they taste different, then you have a problem. CafeLotta's post above gives a good rundown on e61 warming. (FWIW, I made a little insulating hood to sit over my e61 group for faster warmup and, hopefully, to reduce variability between shots, but I never got around to testing that second bit.)

    Adjustability is only really relevant once you have repeatability across shots. Adjustability isn't really all that necessary to brew great coffee. I have an e61 HX at the office and a very adjustable machine at home and I enjoy coffee at both places. What happens is this: if you can't fiddle with things easily on your machine, you will optimise everything else to perform best on your machine and you will probably get good results if your machine can deliver repeatability across shots and generally doesn't suck. You will probably find that there is one particular roaster that you think is god's gift to coffee and that you disagree violently with someone else on the internet who likes some other roaster. You will probably find that if you take your coffee and extract it on their machine, you hate it. If you can fiddle with settings easily on your machine, then what actually happens is this: you fiddle with too many things at once and make your coffee taste bad without being able to pinpoint why. Occasionally, you will get great coffee. But if you can fiddle with settings easily on your machine, then the practical difference should be that once you have enough experience you can adjust your machine to get good results out of a wider array of coffee.

    So I don't think that anyone needs to despair that they will never get good results if they don't have a temperature adjustable machine. Equally, I don't think it's fair to run around saying the emperor has no clothes.
    Good read Luca, you've summed the issue up very well.

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    Quote Originally Posted by luca View Post
    There are at least three different temperature concepts that need to be distinguished: stability during a shot, repeatability across multiple shots and adjustability.

    So I don't think that anyone needs to despair that they will never get good results if they don't have a temperature adjustable machine. Equally, I don't think it's fair to run around saying the emperor has no clothes.
    G'day luca

    Well said. I removed the rest of your excellent post to leave your brilliant parting message as it should be stated more often. Oh, I reckon your adjustability part needs a little more reinforcement (see below).

    Barista consistency - most newbies develop that with time if trained properly.
    Machine temp consistency - most PID machines are at least consistent in their temp profile. I sometimes reckon that is why they make such a difference as some machines (i.e. my long departed Miss S) are pretty diabolical by varying massively as they warm up. Some other well regarded machines are just plain wrong at all times.


    Quote Originally Posted by luca View Post
    Adjustability is only really relevant once you have repeatability across shots. Adjustability isn't really all that necessary to brew great coffee. I have an e61 HX at the office and a very adjustable machine at home and I enjoy coffee at both places. What happens is this: if you can't fiddle with things easily on your machine, you will optimise everything else to perform best on your machine and you will probably get good results if your machine can deliver repeatability across shots and generally doesn't suck. You will probably find that there is one particular roaster that you think is god's gift to coffee and that you disagree violently with someone else on the internet who likes some other roaster. You will probably find that if you take your coffee and extract it on their machine, you hate it. If you can fiddle with settings easily on your machine, then what actually happens is this: you fiddle with too many things at once and make your coffee taste bad without being able to pinpoint why. Occasionally, you will get great coffee. But if you can fiddle with settings easily on your machine, then the practical difference should be that once you have enough experience you can adjust your machine to get good results out of a wider array of coffee.
    Temp stability - Yep, and the jury is still out on how critical that is, and whether (and how) it should be varied during the shot. Ditto pressure profiling.
    Adjustability - Nice to have, not really needed "once you have it right" - whatever that means. As long as you do not ever change your gear, roasts and every farmer can deliver exactly the same crop year after year... looking upwards for flying pigs.

    In the 4 1/2 months it took me to get a Strada* to dance a major issue was losing my frame of reference. I ended up placing my manual lever Electra on the bench next to it to help in that process - and to see if I could match the Electra in the cuppa. I couldn't. The severe learning process at that time called into question the old 92 Celsius at 9 bar for 25(ish) seconds mantra as none of the better light to medium roast shots were done that way. The real issue with both the Strada and, more recently for me, the DE1 is that for such powerful machines they are incredibly sensitive to different roasts (totally unlike the LM Linea - the "Mack truck" of makers for cafe use, which is comparatively "roast indifferent"). I think of the standard machines as like an axe, and the true manual levers (La Pav Pro, Electra and Olympia Cremina specifically from first hand usage) plus the Strada and DE1 are like switching to scalpels. Not for the faint hearted as you also must obey all their quirks to get the benefits. Having said that the rewards are worth it.

    After a while, I realised that those machines could pull great shots on certain roasts when standard machines simply could not. One often overlooked major factor in producing a cuppa is the relationship between the density of the coffee bean (compare a Brasil to an Ethiopian - from sponge to rock) and the solubility (dark roasts are more soluble than lighter roasts). That means that a "one size fits all" machine is about a useful as a "universal fitting shoe" - especially at the extremes.

    A recent example: I bought some Ecuadorian coffee for the first time. It smelt brilliant (salivating at the memory now), and was just over twice the going rate for most roasts at the time - and my roaster reckoned it was worth every cent "when you get it right". The beans were among the smallest I have ever seen, and they were as heavy and hard as bullets (possibly even more dense than most Ethiopians). To make them even less soluble, they were a very light roast. My initial thought was to grind them a lot finer than the Colombian they replaced (good call...). Once I nailed that roast I took them to a friend's ECM. Total fail, even using the same Vario I used on the DE1. The needed profile was just too far off the beaten track for her machine to cope. So back at home I tried them on my trusty old 6910 - still a sink shot. She then had a cuppa on the DE1 and it literally blew her mind - not a surprise, she has really good taste and that Ecuadorian is a total stunner - at 40 seconds of 0.5ml / second preinfusion at 95 Celsius (which it cannot reach due to the cold puck, just brings the puck up to temp faster), a ten second pause, a slow pour at 89 Celcius, 7 bar declining down to 4 bar and for 40+ seconds of shot time to get 21ml out of my 7g single.

    Note: that Ecuadorian is the best new roast I have had since a Sulawesi Blue I first encountered in the '90's. It is that good. The roaster's last batch of Ecuadorian from this harvest is going into my Vario now - hopefully the farmer can equal it on their next harvest (and get paid bucketloads of cash for producing such a great coffee).

    So your last sentence "But if you can fiddle with settings easily on your machine, then the practical difference should be that once you have enough experience you can adjust your machine to get good results out of a wider array of coffee." is also right on the money. Well written, please contribute more...

    Enjoy your cuppa - as long as it is to your taste the world is a better place.


    TampIt
    Strada* - temp and pressure profiling machine from LM, such a leap forward in technical terms of controlling and repeating a shot.

  21. #21
    Senior Member CafeLotta's Avatar
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    Quote Originally Posted by luca View Post
    There are at least three different temperature concepts that need to be distinguished: stability during a shot, repeatability across multiple shots and adjustability.
    These concepts were discussed under the section "How important is Precision" in this Home Barista article -
    https://www.home-barista.com/espress...iler-type.html

    In the article, the various temp stability characteristics of the more common designs of Prosumer Coffee machines was also discussed.

    The concept of repeatability to me suggests that as best as you can, no variables are altered between subsequent shots. As discussed in the article, different machine designs have their own idiosyncrasies and temp stability therefore can vary. To what degree this occurs with high to low temp fluctuation during the shot and how this affects the repeatabilty of flavor in a succession of shots, may be just academic to some. My interest in having more control of temp during brewing on my machine is based on what I was tasting at different brewing temperatures with the same bean. Keeping the temp variation low during the duration of the shot meant for me, going up or down in 1 or 2 deg C increments between shots, the differences in flavor were usually easier to detect and I could find my preferred Brewing Temp quicker. This is where Adjustability comes into play. If Temp is the variable that is hampering repeatability and changing flavor, the easier and more accurately you can control it, surely the better the consistency?
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  22. #22
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    Quote Originally Posted by CafeLotta View Post
    This is where Adjustability comes into play. If Temp is the variable that is hampering repeatability and changing flavor, the easier and more accurately you can control it, surely the better the consistency?
    I'm not sure if you're suggesting that we disagree, but I think we don't and there are two different concepts here: adjustability and repeatability. What I said was:

    Quote Originally Posted by Luca
    So I don't think that anyone needs to despair that they will never get good results if they don't have a temperature adjustable machine.
    I never said that it's OK to have a machine that can't repeat shot temps shot after shot. That's a problem!

    So, to give a few more examples of what I'm saying:

    0) Machine with low repeatability and low adjustability. Eg. Single boiler machine with wideband thermostat or a thermoblock machine with wideband thermostat. Or a HX that overheats and a user that doesn't know how to flush it to get to the right temperature. Result: Big problem. Getting a shot at a suitable temperature for any coffee is a crapshoot.

    1) Machine with repeatability and no adjustablity. Eg. E61 HX with finely tuned thermosyphon restrictor and pstat that is always left on for at least 45 minutes before use and is never used to make more than 1 double shot in 10 minutes and the shot volumes are always similar. Result: Not a huge problem; if the temperature is in a decent window, you'll find suitable roasts that taste good on it. Not a great machine if you want to try lots of different coffees with different roast style.

    2) Highly adjustable machine with poor repeatability. Eg. Tiny single boiler machine with a very wide band thermostat on it (eg +/-3C and then laggy element so you get another second crack overshoot) and a hole punched in the case so you can adjust the thermostat super easily with a screwdriver (note: don't do this on my recommendation - you'll probably electrocute yourself). Result: Problem. If you extract a shot immediately after the element goes off, you'll be way above your target temp. If you extract just before the thermostat switches the element on, you will be way under. You can adjust the temperature to your heart's content, but that won't enable you to just walk up to the machine at any time and pull a great shot.

    3) Highly adjustable machine with great repeatability. Eg. DB saturated group machine or DB e61 machine where you always wait a long time after changing temps before pulling shots. Result: Great. Once you know what you're doing, you can dial in a wider array of coffees.

    Personally, I'm endlessly curious when it comes to coffee, so I try a tonne of different coffees and certainly feel that I can use pressure and temperature adjustments to dial in different coffees. But I've been making espresso for like 20 years. Some people just want an espresso machine, not a religion, hobby or new way of life - if they've got a machine that delivers repeatability and is set to a sensible temperature range then they'll probably be pretty happy and I don't think that they need to spend more money to be able to produce some coffee that they enjoy.

    Whether or not any particular machine delivers the goods is a question that years of internet coffee forum experience has taught me not to touch with a barge pole. Fanboys, I'm sure your machine is the best! Vendors, your misleading and deceptive claims about your machines are safe with me! I'm sure everyone's HX has a finely tuned thermosyphon and pstat and that it is set to "the" optimum temperature! *rolls eyes* *ducks for cover*
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  23. #23
    Senior Member CafeLotta's Avatar
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    Quote Originally Posted by luca View Post
    I'm not sure if you're suggesting that we disagree, but I think we don't and there are two different concepts here: adjustability and repeatability.
    I don't think we're disagreeing?

    Carrying on from an earlier discussion in this thread re: evolution and "if it ain't broke, don't fix it", I was still trying to look at it through the eyes of someone who might be early on in their coffee travels. In regard to temp control, I was suggesting that rather than having to go through the trials of learning how to Temp Surf, develop flush routines etc, for machines that require this to achieve "reapeatability" of brew temp, a much easier option is a machine with a PID'd brew boiler. This would largely remove the temp variable in the "repeatability" equation, which a lot of newcomers seem to run into.

    Sharing my observations was purely to demonstrate why I think aside from brew temp "Stability", easy "Adjustability" (via PID) is a desirable quality in a machine. Initially to set and forget and there for later to experiment with. I don't have it so need to Temp Surf to get the best results that I can. BTW, not a huge fan of my VBM Single Boiler. Learned how to best live with it, that's all.

    Quote Originally Posted by luca View Post
    I never said that it's OK to have a machine that can't repeat shot temps shot after shot.
    I didn't say that you did? The comment on Temp Stability characteristics in the earlier post was included as additional info for the benefit of anyone not familiar with what the different designs of machines have to offer (or not). I do understand the different characteristics of machines as you've outlined. Maybe it's just a matter of semantics.
    Last edited by CafeLotta; 3 Weeks Ago at 07:24 PM.

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    Sorry, I just kind of didn't really understand what you were saying.

    I think that you're saying that a PID gives both repeatability and adjustability. This is true to some extent, but what I'm trying to avoid is newbies shelling out for stuff that doesn't give a meaningful benefit for them. PIDs control temperature only at the point at which they measure it, so if you're controlling it at a sensible point in a machine with a good design for that, like a dual or single boiler saturated group or boiler on group machine where the temperature at the head has a pretty linear relationship with the temperature at the top of the puck, then the PID might get less variance in temperature between shots. I don't know if that's the case with a PID controlled HX as compared with an e61 HX with a decent pressurestat - what people have told me is that the advantage of the PID of essentially making the deadband non-existent is pretty much illusory because the thermosyphon and mass of the head basically average out the impact of the deadband on the pstat. In other words, in this instance, a PID might improve adjustability, but not repeatability. If that is true, a PID HX might be better in terms of adjustability, but not in terms of repeatability and, so, if a newbie has an e61 HX that is already running at a good temp for the coffee they are using, then they might not experience any meaningful improvement in quality in going to a PID instead of a pstat on that machine or a similar one. Basically, I would hate people to read this thread and then sell their machine to upgrade for a benefit that might not be a real benefit to them in the cup.

    I think that you do raise a good point about buying for future capacity. I haven't really had a close look for a long time, but it looks like the cost difference between a pstat e61HX and a PID e61HX or a PID dual boiler isn't as big as it used to be. So anyone who is spending in the zone of an e61HX should definitely be considering a machine that will allow them to play with brew temperature down the track.
    Last edited by luca; 3 Weeks Ago at 08:30 PM. Reason: (Added extra point)

  25. #25
    Senior Member CafeLotta's Avatar
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    Quote Originally Posted by luca View Post
    Sorry, I just kind of didn't really understand what you were saying.

    I think that you're saying that a PID gives both repeatability and adjustability.
    I made the comment in reference to a machine with PID control on the Brew Boiler, not on a Hx machine with PID control on the Service/Steam boiler.

    The Repeatability reference is in relation to the Brew Temp component of the overall shot repeatability equation. PID temp control on the Brew Boiler provides good Brew Temp Stability with little variation in Temp during a shot. Adjustability of your target brew temp is obviously easier with PID.

    I'm not saying you can't achieve Brew Temp repeatability with non-PID machines, just that in a lot of ways it's generally easier with a PID controlled Brew Boiler. Shouldn't be a need for flush routines or Temp Surfing.

    One thing I've always wondered is why Domestic Hx machines don't have the Hot Water tap/arm drawing from the top of the Exchanger (maybe a tee before the grouphead connection) rather than from the Service boiler. This would allow over heated water in the exchanger to be drawn out from before the E61 grouphead if a machine has been sitting idle for a prolonged period. This might help to avoid overheating the grouphead at times. I think it might be worth the trade off of not being able to draw Hot Water at the same time as Brewing.

    Quote Originally Posted by luca View Post
    I think that you do raise a good point about buying for future capacity.
    People need to do their research after being honest about what their personal requirements are. Once you've narrowed you're list down it's also worth checking on servicing costs for your chosen machines with the service centre you'll be using. Also look at resale on your model/brand if that's important to you as some will devalue faster than others. As to what offers best bang for buck, you'll always get varying opinions. Mine is only a single opinion.
    Last edited by CafeLotta; 3 Weeks Ago at 11:38 AM.
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  26. #26
    Senior Member Yelta's Avatar
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    I would like to thank CafeLotta, he very generously contacted me about a week ago and offered me an unused Coffee Sensor, rather than misquote his offer to me, here is part of the PM he sent.
    "Hi Jon,
    Don't know if you've ever tried a grouphead thermometer? I have one of the earlier model standard CoffeeSensors which Tudor sent me last year to try out. As it's surplus to my needs and was a freebie, you're welcome to have it if you're curious. It has a shorter main body than the current 2019 model but it seems this was mainly an issue on VBM E61 Groupheads. I needed a stack of washers to get clearance to external surfaces when seated correctly. (it then leaked). Tudor has lengthened the body on the 2019 model but said that the older design worked fine on a number of other machine brands. https://coffee-sensor.com/product/te...er-2019-model/ "


    Needless to say I gratefully accepted his offer, the sensor arrived yesterday and I fitted it to the Bezzera without any problem, certainly no leakage.

    Early days yet, however it certainly is interesting to see the temperature variations, seems the machine hovers around 90C when idling, however does fluctuate by as much as 7 or 8 depending on just how long the machine has been on, obviously the water in the boiler heats to a higher temp than I'm seeing at the group head at idle, trying to make sense of readings at at the moment, will report back after using the device for a while.

    Thanks again CafeLotta and the Coffee Sensor company.
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  27. #27
    Senior Member CafeLotta's Avatar
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    Quote Originally Posted by Yelta View Post
    Tudor has lengthened the body on the 2019 model but said that the older design worked fine on a number of other machine brands. https://coffee-sensor.com/product/te...er-2019-model/
    Just noticed that link isn't working. His link for the current 2019 model is - https://coffee-sensor.com/product/te...er-2019-model/ These are great value and are on par performance wise to TheBat device grouphead thermometer.

    Site Sponsor CoffeeSensor also offers this version - https://coffee-sensor.com/product/di...s-pro-version/
    I'm currently using one of these and it's the best value fully depth adjustable quick response Grouphead thermometer available.

    Quote Originally Posted by Yelta View Post
    Early days yet, however it certainly is interesting to see the temperature variations, seems the machine hovers around 90C when idling, however does fluctuate by as much as 7 or 8 depending on just how long the machine has been on, obviously the water in the boiler heats to a higher temp than I'm seeing at the group head at idle, trying to make sense of readings at at the moment, will report back after using the device for a while.
    I'd imagine the 7 or 8 deg fluctuation would be due to the increased water temp in the Heat Exchanger after sitting idle and exposed to the Service/Steam boiler temp for an extended period. This is then circulated through the E61 Grouphead via the Thermosyphon circuit, increasing the grouphead temp at idle also.

    Running some water through the Heat Exchanger to lower water temp inside the Exchanger and then allowing a few minutes for the Temp of the E61 Grouphead to stabilise should show a more static Brew Temp I'd imagine?

    E61 Hx Generic.jpg

    https://www.home-barista.com/tips/th...ine-t4862.html



    P.S. Thought I might also add this link for any Hx machine owners who may like to see inside a typical Hx boiler. This video shows the internals of an E61 grouphead as well and the connections to the exchanger. Has been posted in the past but could be of interest to those who haven't seen it.

    https://www.youtube.com/watch?v=2jn28YTS3OQ
    Last edited by CafeLotta; 2 Weeks Ago at 10:24 AM. Reason: P.S. added link for E61 Hx machine cutaway
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  28. #28
    Senior Member Yelta's Avatar
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    Something I have certainly discovered since fitting the Sensor is how much longer the machine takes to reach operating temperature from cold in colder weather.

    Its been colder than a mother in laws kiss down here over the past few days, takes the machine approx 45 mins to get to 90C from cold, I'm sure it heats a lot faster during the summer months, will be interesting to compare.
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  29. #29
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    Nothing like a small injection of science to dispel long held beliefs...

    Mal.
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  30. #30
    Senior Member CafeLotta's Avatar
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    Quote Originally Posted by Yelta View Post
    Something I have certainly discovered since fitting the Sensor is how much longer the machine takes to reach operating temperature from cold in colder weather.

    Its been colder than a mother in laws kiss down here over the past few days, takes the machine approx 45 mins to get to 90C from cold, I'm sure it heats a lot faster during the summer months, will be interesting to compare.
    I find I can still keep heat-up to around 30 mins if I do a couple of early flushes through the grouphead and portafilter once the boiler is up to temp. This gets some heat into the grouphead and portafilter quickly on those colder days.
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  31. #31
    Senior Member Yelta's Avatar
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    Behmor Brazen - $249 - Free Freight
    Quote Originally Posted by CafeLotta View Post
    I find I can still keep heat-up to around 30 mins if I do a couple of early flushes through the grouphead and portafilter once the boiler is up to temp. This gets some heat into the grouphead and portafilter quickly on those colder days.
    Doesn't present any problem, 30 mins 45 mins, not really important, by the time I've attended to a couple of the morning chores it's ready to go, life is pretty leisurely in retirement.

    I'm aware the heating process can be accelerated, I simply don't need to do it.

    Ambient temperature also has a dramatic affect on roasting in the Coretto, as well as many other household activities.
    Retired.png
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