# Use of Technology in Espresso making equipment



## Charliej (Feb 25, 2012)

As my question got lost in the debate about Has Bean I'm going to put it in a new thread.

Several people have said they are all for new uses of technology if they make it easier and more consistent to produce good results in the cup so here's one discussion to start the thread off.

A quick take on the technology vs tradition. Using my Gaggia Classic every one in a while when every factor needed is in alignment I can make a truly wonderful coffee, using the Sage I can make that wonderful coffee every shot.

I have got a point I would like to open for discussion on this thread:

Can anyone give me a cogent and reasoned argument why a system that has a PID on the brew boiler and uses a thermosyphon to control the group temperature, should be any more thermally stable than one that uses a PID on a smaller brew boiler that is fed water pre heated by an HX in the steam boiler and also uses a PID on the electrically heated group, given, that we all accept that a PID can keep a brew boiler to the selected temperature more accurately, even a cheap chinese PID off ebay will do this. I.E is the E61 group or any thermosyphon heated group the pinnacle of espresso making or can more modern methods achieve equal or better result


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## Geordie Boy (Nov 26, 2012)

Nothing wrong with putting a heater in the group, sounds like a great design feature to me


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## CoffeeDoc (Dec 26, 2012)

When designed the E61 was the peak of technology, if you look back at the first espresso machines I doubt if you would ever get what we would call a really good espresso from them and if you did it was more luck than judgement. Bean 2 cup machines use technology but perhaps not wisely in terms of final output but make life convenient, a heater in the group head may be technology used for quality not convenience.

Paul


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## Geordie Boy (Nov 26, 2012)

Paul, I think a group head heater is there for convenience (as the warmup time due to thermal lag is reduced by applying direct heat not waiting for another heat source to warm up). My machine has one and I think it's great as I don't have to bother with warming flushes but just press the on button and wait 15 mins. Does it affect the shot quality compared to if the design didn't rely on it, honest answer is that I've no idea, however my hunch is that it wouldn't


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## 4515 (Jan 30, 2013)

Is the PID there for more accurate temperature or to offer the ability to vary temperature ? Asking as I dont know the answer here

If technology can work around bad technique does this make us sloppy in our routine ?

Analogy time. Driving a car with ABS, traction control and the likes can make you look a better driver but also takes the soul out of driving - Lotus 7 vs latest euro wagon.

I've pulled some terrible shots but when I hit the sweet spot theres a sense of satisfaction that I created it. Not sure if I'd get the same feeling if (song time) some machine is doing it for you

Just my personal thoughts. Initial comparisons are very favourable for the Sage and I'm sure that Mrs WD would be more inclined to use one. Coming from a mechanical engineering background, my calling lies elsewhere


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## 4085 (Nov 23, 2012)

I think the PID is there so that you can set the temperature. Some beans respond in a different way to just small fluctuations


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## Geordie Boy (Nov 26, 2012)

A PID does also give better temperature control even if you don't want to vary the temperature (e.g. compared to a pressure stat system). That's why the more 'top end' HX machines have them even though you wouldn't tend to change the temp on them


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## RoloD (Oct 13, 2010)

Charliej said:


> Can anyone give me a cogent and reasoned argument why a system that has a PID on the brew boiler and uses a thermosyphon to control the group temperature, should be any more thermally stable than one that uses a PID on a smaller brew boiler that is fed water pre heated by an HX in the steam boiler and also uses a PID on the electrically heated group, given, that we all accept that a PID can keep a brew boiler to the selected temperature more accurately, even a cheap chinese PID off ebay will do this. I.E is the E61 group or any thermosyphon heated group the pinnacle of espresso making or can more modern methods achieve equal or better result


A good question. I'm not an engineer, but I'm going to answer by asking some more questions:

What temperature is the PID actually measuring? The boiler water? The boiler walls? Water and steam are bad conducters of heat, which is why pressurestats rather than thermostats are preferred in HX designs. Most PID designs are, I believe, based on temperature. So steady PID readout does not necessarily correspond with steady temperature of water as it passes through the coffee.

In a classic HX design you have a lot of metal that is storing, conducting and radiating heat. Because there is a lot of metal, temperature change is not going to happen rapidly. The water is not just the end product, the temperature of which you are trying to control, it also the medium for controlling temperature as it flows through the system. This is a complex dynamic system and the best designs evolve through practical development.

This suggests to me that a modern electronic approach would be to have a low-mass system where temperature can be monitored and constantly and adjusted very fast against a more traditional system that has a high mass which takes longer to reach optimum temperature but will then become inherently stable. Some of the most sophisticated commerical espresso machines have, I believe, aspects of both.

In addition, many would argue that, during extraction, you want a diminishing temperature and pressure profile rather than a constant one. This either means a mechanical design, like a sprung lever, which inherently creates such a profile or a some fairly complex electronics. Which is a 'better' approach? You tell me.

But, I repeat, I am not an engineer, but these notes are partly informed by having owned both a PID-controlled Classic (not much mass of metal but numbers that tell you everything is stable) and lever group with no electronics but a group which is 7Kg of brass.


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## Geordie Boy (Nov 26, 2012)

RoloD said:


> What temperature is the PID actually measuring? The boiler water? The boiler walls? Water and steam are bad conducters of heat, which is why pressurestats rather than thermostats are preferred in HX designs. Most PID designs are, I believe, based on temperature. So steady PID readout does not necessarily correspond with steady temperature of water as it passes through the coffee.


For boiler temperature, you'd ideally put the temperature feedback probe inside the boiler so you'd be using a more accurate measurement point of the thing you're trying to control (i.e. the temperature inside the boiler where the HX happens). For the Classic PID mod, I'm guessing you have to bond the sensor to the outside wall of the boiler so I agree that you're adding in problems w.r.t. heat transfer between fluids and metal, and keeping the metal mass small is (as you say) probably an advantage in controlling water temperature.

The other thing that springs to mind is that the boiling point of water does change with pressure. Say the pressure inside a HX boiler is controlled between 1.31bar and 1.17bar by a pressure stat, that's a difference of 3degC in boiling point (between 1.31bar and 1.10bar it increases to 5degC), so can we assume that the temperature inside can change by this amount? Does a PID keep this temperature more stable? To me, a pressure stat is a control method that has a large deadband in it's control (i.e. turns off the element when pressure reaches x bar, turns it back on when it reaches y bar) and thus is simple. A PID by it's nature is more dynamic in it's control and won't have as large a deadband as it's constantly working out what it needs to apply (heatwise) to keep the temperature stable. It also knows the time from turning the element on to it actually having an effect so uses this in it's control calculations.

I must add that I'm not an expert at this so I am willing to be wrong, however there's some interesting questions in this thread!


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## RoloD (Oct 13, 2010)

Geordie Boy said:


> Say the pressure inside a HX boiler is controlled between 1.31bar and 1.17bar by a pressure stat, that's a difference of 3degC in boiling point (between 1.31bar and 1.10bar it increases to 5degC), so can we assume that the temperature inside can change by this amount? Does a PID keep this temperature more stable? To me, a pressure stat is a control method that has a large deadband in it's control (i.e. turns off the element when pressure reaches x bar, turns it back on when it reaches y bar) and thus is simple. A PID by it's nature is more dynamic in it's control and won't have as large a deadband as it's constantly working out what it needs to apply (heatwise) to keep the temperature stable.


 This is true, but the PID is only measuring the temperature of water at one point in the boiler or (in the case of a thermoblock design like the Classic) of the boiler walls themselves. So the PID might be adjusting the heat at one point but measuring it at another which introduces a few more variables.


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## dsc (Jun 7, 2013)

This is an informed guess, my background is control engineering, but I don't know enough about thermosyphons to offer a 100% sure answer. In my opinion you can PID a boiler, but in order to produce consistent temperature you need to think about how cold water is fed and what the heater can do. On a tiny boiler, the heater can only do so much, if you keep feeding it cold water, you'll bring the overall temperature down as the incoming water will simply flow through the boiler and not have enough contact with the heating element. If you feed pre-heated water it will be better, but still limited by the overall design, water path, size, heating power and water flows.

Breaking down the system you have:

1. HX pre-heated water - normally super hot, boiling. If you pull a cooling flush, this will lower the temperature in the HX but effectively increase temperature in the rest of the system. You are passing boiling water through the whole boiler and group. Remember, there's no way to cool down components

2. Small boiler - see what I said above, a small capacity of water will heat up quickly and remain at a steady temperature. As soon as you start flowing water though it, you are changing the temperature. If you set up your PID to maintain temp at an idle state, be sure to see control problems when things get chaotic ie. when pumping water. The conditions will change, but the PID will still want to control as if it's simply warming a tank full of water. If the water flow through the boiler is high, the heater won't keep up and PID will do what it can with poor results. From a PID point of view you are moving from an object which is rather quick to respond to an object which is almost impossible to respond due to flow. The bigger the boiler the better as you have a buffer and the tank cools down slower.

3. Group heater - this is a lump of metal, most likely connected to the boiler if it's a small machine. Any more metal close to the group will affect how it performs thermally, if you overshoot with temperature, the only way to cool it down will be to turn of the heater, although it will most likely still get heat from something around it. The lag will be quite high.

The overall conclusion is that you need everything at the same steady temperature with enough thermal capacity to maintain it when in contact with cooler water, or have a variable temperature system which is designed properly and allows for quick temperature changes regardless of variables like incoming water temperature, water flows etc.

Regards,

T.


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## Charliej (Feb 25, 2012)

Ok to shift the question back to my original one as it was regarding a dual boiler machine that has a small (330ml) brew boiler fed pre heated water at 80 degrees, via an HX in the 950ml steam boiler. The dual PIDs have a sensor IN the boiler and in the head, they are there both to allow variance of temperature and temperature stability. If you pull a shot of the sort of volume most of us do which would be 30-45ml as an average guess then adding this amount of water heated to 80 degrees into the brew boiler should really have very little effect as we are only talking about 10-15% being added to the brew boiler.

I have still not seen any real "arguments" as to why an E61 offers better control and stability than a microprocessor controlled setup designed and integrated into the machine, not something added on to a Silvia or Classic.


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## RoloD (Oct 13, 2010)

Charliej said:


> Ok to shift the question back to my original one as it was regarding a dual boiler machine that has a small (330ml) brew boiler fed pre heated water at 80 degrees, via an HX in the 950ml steam boiler. The dual PIDs have a sensor IN the boiler and in the head, they are there both to allow variance of temperature and temperature stability. If you pull a shot of the sort of volume most of us do which would be 30-45ml as an average guess then adding this amount of water heated to 80 degrees into the brew boiler should really have very little effect as we are only talking about 10-15% being added to the brew boiler.
> 
> I have still not seen any real "arguments" as to why an E61 offers better control and stability than a microprocessor controlled setup designed and integrated into the machine, not something added on to a Silvia or Classic.


Well an E61 is a type of group, not a boiler system, and is often found on Dual Boiler designs like the type you are describing. If you are asking what advantages a single boiler HX has over a Dual Boiler PID I think, in theory, very little other than simplicity. If you look at sophisticated commercial machines, some have separate steam boilers, some don't. Some have HX systems combined with group heaters. On a domestic level, Dual Boilers cost a little more money (the exception is the DB Fracino Piccino which is cheaper but also regarded as inferior to the HX Cherub) and some might have less steam power than the equivalent HX design. So I agree, in principle a microprocessor controlled set-up should give the best results.


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## Charliej (Feb 25, 2012)

RoloD said:


> Well an E61 is a type of group, not a boiler system, and is often found on Dual Boiler designs like the type you are describing. If you are asking what advantages a single boiler HX has over a Dual Boiler PID I think, in theory, very little other than simplicity. If you look at sophisticated commercial machines, some have separate steam boilers, some don't. Some have HX systems combined with group heaters. On a domestic level, Dual Boilers cost a little more money (the exception is the DB Fracino Piccino which is cheaper but also regarded as inferior to the HX Cherub) and some might have less steam power than the equivalent HX design. So I agree, in principle a microprocessor controlled set-up should give the best results.


Even though the E61 is a group it is part of the overall system aimed at making thermal stability better, the heart of my question is about any system that uses boiler water to heat the group head vs a modern system that uses a dual PID to control both brew boiler and group temperatures. To put it simply is E61 or any other thermosyphon based system the peak of espresso technology or can we do better with modern microprocessor controlled systems, and I would like to state from the off that this is not like the valves vs solid state argument in audio forums, this also not about knocking one system over an other, I am after factual reasons not emotive ones.


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## dsc (Jun 7, 2013)

Charliej said:


> Ok to shift the question back to my original one as it was regarding a dual boiler machine that has a small (330ml) brew boiler fed pre heated water at 80 degrees, via an HX in the 950ml steam boiler. The dual PIDs have a sensor IN the boiler and in the head, they are there both to allow variance of temperature and temperature stability. If you pull a shot of the sort of volume most of us do which would be 30-45ml as an average guess then adding this amount of water heated to 80 degrees into the brew boiler should really have very little effect as we are only talking about 10-15% being added to the brew boiler.
> 
> I have still not seen any real "arguments" as to why an E61 offers better control and stability than a microprocessor controlled setup designed and integrated into the machine, not something added on to a Silvia or Classic.


Ok a few things first:

- why are you saying the water is preheated in the HX in the steam boiler to only 80degC? the steam boiler is held at high temperature above 100degC, so any water left in the HX will be boiling / part steam. Where does the 80degC figure come from?

- water from the HX enters the brew boiler, is that connected to the group ie. is it a group - boiler design, or a separate group fed via tubes from the boiler?

- where's the sensor in the head? front, back, embedded inside, near the feeding tubes, near the dispersion screen?

- what heats the group apart from brewing water? is it electrically heated, if so, where's the heater, is it surface mounted or again embedded in the group itself?

You are describing a system which has many elements, all of which have thermal mass, heaters have different heating efficiencies etc. that introduces lag, delays in heating, overshot etc. it's not as easy as turning a heater on and instantly getting a result, especially if you have several components at different temperatures. It's all nice and dandy when it sits at idle, just ticking over keeping the temps steady, but as soon as you introduce water at a temperature different than the components, you cause an interference.

From a theoretical point of view, it is possible to design a PID based system which will deliver constant temperature for a long period of time, whether it's possible with the machine you describe is not so easy to answer or even impossible without knowing more details about the design, thermal conductivity of certain element connections, idle running temperatures with standard non-PID controls etc. You have to remember, microcontrollers can quite easily control a lot of variables at the same time, but how efficient it all is, is down to the limitations of the equipment / instrumentation.

Regards,

T.


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## Charliej (Feb 25, 2012)

OK the 80 degrees is the figure quoted by the manufacturers for the temperature of the water fed to the brew boiler, sensors for the brew boiler and head are both internal as are the heating cartridges for the group heater, from the block diagram, (haven't taken the top off) it appears that the boiler is vertically above the group but I don't know how it is attached, with a dual PID system to me it would make sense to have it connected to the group, the brew boiler element is a spiral shaped one and again appears to cover pretty much all of the boiler sides. To the best of my knowledge the metal used for both boilers, HX and group is stainless steel as is the PF itself, and we aren't talking about a particularly cheap machine here, and it was designed with input from professional baristas in Australia and coffee enthusiasts and I am led to believe experiences designers.

I still want to know why a thermosyphon based system would be inherently any more stable.

Tom just a quick one I am very familiar with microprocessor based systems and what a well designed and cheaply designed system can be like. I have, though forgotten pretty much all of the thermodynamics and fluid dynamics stuff I learnt about in both O and A level physics as its many many years ago so all that has stuck are the parts I need to know relevant to work.


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## Geordie Boy (Nov 26, 2012)

Charliej said:


> I still want to know why a thermosyphon based system would be inherently any more stable.


You can always improve on things, be it by tweaking the existing technology or by discovering a completely different way to do things. How can someone answer that a thermosyphon system will be more stable against new technology that they probably haven't tried?


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## RoloD (Oct 13, 2010)

I don't think anyone has suggested that a 'thermosyphon based system would be inherently any more stable' than an electronically controlled one, just that a well-designed, proven thermosyphon can be better than a poorly implemented PID design. There also may be practical and economic advantages to having one large boiler rather than two smaller ones.


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## Charliej (Feb 25, 2012)

RoloD said:


> I don't think anyone has suggested that a 'thermosyphon based system would be inherently any more stable' than an electronically controlled one, just that a well-designed, proven thermosyphon can be better than a poorly implemented PID design. There also may be practical and economic advantages to having one large boiler rather than two smaller ones.


Hmm but what then for other respected DB machines such as the R58, Expobar Brewtus and all the other multi boiler commercial machines.

Assuming that the PID system isn't poorly implemented, and there is no reason to assume poor implementation, as after all PID control of temperature is well established in industry and when designed into a machine to perform a job should do what it's supposed to, after all everyone accepts that a Classic or a Silvia can be improved with a DIY kit, whether bought as a kit or as parts. I for one see anything offering better temperature stability or the promise of such as a good thing.


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## RoloD (Oct 13, 2010)

Charliej said:


> Hmm but what then for other respected DB machines such as the R58, Expobar Brewtus and all the other multi boiler commercial machines.
> 
> Assuming that the PID system isn't poorly implemented, and there is no reason to assume poor implementation, as after all PID control of temperature is well established in industry and when designed into a machine to perform a job should do what it's supposed to, after all everyone accepts that a Classic or a Silvia can be improved with a DIY kit, whether bought as a kit or as parts. I for one see anything offering better temperature stability or the promise of such as a good thing.


I'm not sure what your argument is here&#8230; I wasn't suggesting PID was poorly implemented in those or any other machines and I have no idea who claimed 'thermosyphon based system would be inherently any more stable' - seems this is a straw man argument. I haven't heard any coherent arguments against PID systems in principle, just that in practice they might not always quite deliver quite what they promise.


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## garydyke1 (Mar 9, 2011)

The Sage stays within 0.1*c* over 30 seconds at max temp (if it does change it gets cooler)

The Expo e61 stays within 0.4*f* over 30 seconds at max temp (if it does change it gets hotter)


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## 4515 (Jan 30, 2013)

If temperature stability isnt spot on and there is a +/- degree or so will this result in bad coffee or different flavour profile ?

From my (limited) experience I have found the biggest gains in quality in the cup from changes external to the espresso machine. I suppose I'm discounting machines with lesser thermal mass from my statement where greater control seems to make a big difference.

Are there any views on a PID'd vs non PID prosumer type machines ? Is there a difference in quality when used at the same temperature ?


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## dsc (Jun 7, 2013)

Charliej said:


> Hmm but what then for other respected DB machines such as the R58, Expobar Brewtus and all the other multi boiler commercial machines.
> 
> Assuming that the PID system isn't poorly implemented, and there is no reason to assume poor implementation, as after all PID control of temperature is well established in industry and *when designed into a machine to perform a job should do what it's supposed to*, after all everyone accepts that a Classic or a Silvia can be improved with a DIY kit, whether bought as a kit or as parts. I for one see anything offering better temperature stability or the promise of such as a good thing.


It all depends on whether the machine is fit for PID control or not, you can have a properly fitted temperature sensor in the tank, highly precise auto-tunable PID and it won't do jack because the boiler is too small, or the heater is efficient enough. PID kits for Silvias and Classics offer improvement as the original solution is to control temperature with a simple thermostat which offers very little precision. A thermosyphon / E61 solution is a non-electrical way of making sure the temperature stays steady for a longer period of time, even though you are supplying fresh water constantly. A PID (or several PIDs) will offer the same, done differently. I don't think anyone said one is better than the other, unless I missed something somewhere.

Regards,

T.


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## Charliej (Feb 25, 2012)

dsc said:


> It all depends on whether the machine is fit for PID control or not, you can have a properly fitted temperature sensor in the tank, highly precise auto-tunable PID and it won't do jack because the boiler is too small, or the heater is efficient enough. PID kits for Silvias and Classics offer improvement as the original solution is to control temperature with a simple thermostat which offers very little precision. A thermosyphon / E61 solution is a non-electrical way of making sure the temperature stays steady for a longer period of time, even though you are supplying fresh water constantly. A PID (or several PIDs) will offer the same, done differently. I don't think anyone said one is better than the other, unless I missed something somewhere.
> 
> Regards,
> 
> T.


 Tom I don't think anybody actually said E61 or thermosyphon is better outright, it has, however, been implied in several of the threads, this is why I asked the question, I just wanted to see some discussion on the matter, and on new technology coming in in general, in machines and grinders, as we do seem to have 1 or 2 Neo-Luddites around.


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## 4515 (Jan 30, 2013)

Charliej said:


> Neo-Luddites around.


And you'll be telling us that the world is round next


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## dsc (Jun 7, 2013)

In my opinion whatever works works, I don't mind a thermosyphon / HX approach, as long as you know how to operate one, I also don't mind a dual boiler with dual PIDs, pressure transducers etc. As long as the machine delivers and it works for your routine, there's nothing to worry about. Btw I don't think dead solid temperature profiles are the best thing possible, from a control point of view, it's a nice thing, but it doesn't mean it delivers the best brew. The other thing is that it's hard to make a custom temperature profile, much easier to keep the temperature steady.

Regards,

T.


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## Charliej (Feb 25, 2012)

working dog said:


> And you'll be telling us that the world is round next


Believe it or not at the church my Mother used to attend before the dementia struck she had a friend who was a fully paid up member of the Flat Earth Society and could truly not accept that the earth is an oblate spheroid, but I can't ever remember flying off the edge even going to Australia via the USA.


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## RoloD (Oct 13, 2010)

Charliej said:


> Believe it or not at the church my Mother used to attend before the dementia struck she had a friend who was a fully paid up member of the Flat Earth Society and could truly not accept that the earth is an oblate spheroid, but I can't ever remember flying off the edge even going to Australia via the USA.


You were just lucky.

I've fallen off that edge many times.


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## RoloD (Oct 13, 2010)

Charliej said:


> Tom I don't think anybody actually said E61 or thermosyphon is better outright, it has, however, been implied in several of the threads, this is why I asked the question, I just wanted to see some discussion on the matter, and on new technology coming in in general, in machines and grinders, as we do seem to have 1 or 2 Neo-Luddites around.


I suppose you could consider lever fans neo-Luddites but I don't think that is the case.

A full-size lever group produces wonderful espresso because of the inherent pressure/temperature profilng that the mechanical design has produced (interestingly, it seems the advantages of profiling/soft pre-infusion in this case outweighs those of temperature stability). State-of-the-art can emulate these profiles (and many others) electronically, just as the E61 was designed (partly) to emulate the lever. Lever machines are beautiful objects in themselves, simple and inherently reliable and, on a domestic level, (arguably) can't be bettered. But when you get to high-end commercial machines with control over every parameter you are in a different league altogether - they can produce results that no electro-mechanical machine could. But maybe because I spend most of my day working with digital technology, there is real pleasure in using a well engineered purely mechanical device.

So who are the Neo-Luddites? Let them step forward and declare themselves!


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## Charliej (Feb 25, 2012)

RoloD said:


> I suppose you could consider lever fans neo-Luddites but I don't think that is the case.
> 
> A full-size lever group produces wonderful espresso because of the inherent pressure/temperature profilng that the mechanical design has produced (interestingly, it seems the advantages of profiling/soft pre-infusion in this case outweighs those of temperature stability). State-of-the-art can emulate these profiles (and many others) electronically, just as the E61 was designed (partly) to emulate the lever. Lever machines are beautiful objects in themselves, simple and inherently reliable and, on a domestic level, (arguably) can't be bettered. But when you get to high-end commercial machines with control over every parameter you are in a different league altogether - they can produce results that no electro-mechanical machine could. But maybe because I spend most of my day working with digital technology, there is real pleasure in using a well engineered purely mechanical device.
> 
> So who are the Neo-Luddites? Let them step forward and declare themselves!


I wasn't accusing lever owners as Neo-Luddites just the people who seem to be nay sayers and dismiss machines with new technology in them out of hand without even so much as a good look at them , this is written by someone who would love to own an L1, but unfortunately never will as apart from a lottery win or a raffle on here I'm most likely going to be stuck in Oscar or Cherub territory, barring a very good deal on an ex demo sage DB lol.


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## aFiercePancake (Dec 8, 2013)

I moved to the opposite end of the spectrum years ago. I have been using lever machines and hand grinders for years and am very content. As long as I do not have to make more than a few shots at a time, the manual setup proves every bit as consistent and probably more reliable than semi-auto setups. There was a time when I was obsessed about temperature and particle sizes, but once I got my routine and setup pat, I decided the simplicity of doing everything myself was far superior to temperature surfing, monthly cleaning, descaling, and the lot. Just my 2p.


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