# Vesuvius Pressure profiling



## DavecUK (Aug 6, 2013)

I need some thoughts here, especially as thers some people loving their levers.

*Background*

Espresso is coffee extracted at 9 bar at between 93-95C...blah blah whatever

Lever machines can produce quite a sweet shot

I have known the above for years and about 7 years ago my thinking was. What's different about levers and I went to find out. As we all know a large commercial lever group will often start the extraction at 11 or 12 bar and then it gradually tails off. Different to an Espresso machine that starts at 9 bar and stays there (forget about unregulated machines for now). Now quite by accident when testing some cheaper and less well regulated machine, I remember pulling a shot at (what proved to be 12 or 13 bar), thinking damm forgot to reset the OPV and check with the pressure measuring portafilter....so stopped the shot short. Thought I might as well try it and took a sip. I was surprised that it wasn't as bad as I thought. hence the investigation into the levers. I never discussed this with anyone or in reviews, because I was never sure why espresso machines were regulated to 9 bar...it didn't really make sense, considering how well levers did. I had a view and my view was that 9 bar was simply a good compromise pressure....too high and the shot would be bitter and harsh, to low and it would lack character and flavour. It seemed logical that pressure should vary during the shot as more was extracted from the coffee. The levers were doing well, because of serendipity (probably), I seriously doubt design, but perhaps it was? I felt coffee definitely needed higher pressures at the beginning and lower pressures as the shot progressed, so lets copy the lever a little bit.

Now we come to the present day and it's easy to forget what we know, or thought we knew. I found that if a high pressure was initially applied, the sudden puck compression was such that it affected the flow and there's just a little something in you not wanting to apply these higher than normal pressures. However, I've been playing with *pump acceleration (PA) as an additional factor to change the speed at which these pressures are applied*. I also watched a number of spring lever videos to remind myself of the technique and it does seem that the remembered technique of following through with the lever and letting it load up gradually was more common than just letting it rise fast until it hit the pressure point. The difference is subtle but it's there. So i revisited the previous less than successful high pressure start profiles and lowered the pump PA right down. The profile I used was as follows *5s 2bar preinfusion, 6 seconds 12 bar, 8 seconds 9 bar, 6 seconds 8 bar and 5 seconds 6 bar all with quite a low global PA.* The PA was critical in allowing me to raise the starting pressure, because I could simulate than safety "hand" on the lever. The resulting espresso has more cremea, slightly darker, even though the temperature had not changed and more sweetness, with a slight touch of pleasant acidity and a citrus backnote. The Coffee was a Medium Dark El - Salvador not noted for sweetness and would normally be low acidity at that roast level. The character of the coffee was changed markedly and it surprised me.


It would also seem logical that extraction is related to grind, so could different pressure declines also allow grind to remain similar and maintain extraction ratios...which of course is the next round of testing I want to try, it just takes so long.

The last logical point would be that different coffees extract differently and hence require different pressure profiles.


I think I'm gradually finding my way with the pressure profiling now...but does any of this make logical sense, anyone have any views?


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## 4085 (Nov 23, 2012)

Dave, thinking about it the other way around, and to widen the problem, is there any sensible differences to the way a lever extracts that could be made to improve it? I do not understand enough to really follow you on pressure profiling discussion but do appreciate the level that the coffee scientists go to!


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## MWJB (Feb 28, 2012)

This is worth a read:

http://www.jimseven.com/2011/02/08/continued-thoughts-on-pressure-profiling/

Extraction is related to grind, but also to rate of flow through the puck?


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## coffeechap (Apr 5, 2012)

Thanks mark that makes interesting reading, I cant offer a definitive answer, all I can say is that the reducing pressure profile of levers produces a very even extraction, the flow remains fairly constant throughout the shot until the very end, unlike constant pressure where the shot speed increases throughout the extraction. some of the best shots that I have acheived on pump driven machines like the brewtus and the rocket giotto have been where I have cut the shot at around the 22 second mark and allowed the completion on purely line pressure. I dont profess to know the ins and outs just that spring lever espresso shots are consistently good.


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## DavecUK (Aug 6, 2013)

MWJB said:


> This is worth a read:
> 
> http://www.jimseven.com/2011/02/08/continued-thoughts-on-pressure-profiling/
> 
> Extraction is related to grind, but also to rate of flow through the puck?


I think I'm on the right track then, my thoughts for years about the compromise of 9 bar vs the compromise of the lever may well be valid in giving the differences. Fortunately flow reduction is a function of the pressure the gear pump delivers, lucky but fortuitous. I guess all methods are a compromise, but at least I've have an opporunity to fine tune the compromise to be repeatable and changeable for different situations/coffees. A lot of what is in that link mirrors my thoughts.

Especially the stuff about puck compaction, as I always felt a puck behaves a little like a non Newtonian fluid...until it's well soaked, for me the jury is out on overly long preinfusion. I have tried very long preinfusion and shorter preinfusions...I find if you go too long the result is not so good. Again a suspicion from the behaviour of a spent puck, do an extraction, release the pressure as gently as possible, then run a second shot...how fast it runs, becuase the puck is so wet. I do wonder if overly long preinfusion gives a puck that "loses cohesiveness" for want of a better word and can't get it back again, even when the pressure goes up.


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## Charliej (Feb 25, 2012)

I've discovered when playing around with the preinfusion time and pressure on the Sage that the longer the preinfusion the faster the shot proper runs i.e. a much higher flow rate through the puck than a lower length of preinfusion. Like Dave (CC) I've found that some of the better shots I've pulled on the Sage have come by cutting the pump and then holding down the manual button to run the rest of the shot at the preinfusion pressure.

DaveC are you considering trying to get the makers of the Vesuvius give more granularity for controlling the flow rate?


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## DavecUK (Aug 6, 2013)

Charliej said:


> I've discovered when playing around with the preinfusion time and pressure on the Sage that the longer the preinfusion the faster the shot proper runs i.e. a much higher flow rate through the puck than a lower length of preinfusion. Like Dave (CC) I've found that some of the better shots I've pulled on the Sage have come by cutting the pump and then holding down the manual button to run the rest of the shot at the preinfusion pressure.
> 
> DaveC are you considering trying to get the makers of the Vesuvius give more granularity for controlling the flow rate?


Flow rate is a function of the gear pump and is dependent on pressure so the lower the pressure the lower the flow, the critical thing about that is the dynamic and hydrostatc pressures generated are essentially the same...which allows for good control control. I have asked about adding more stages. 5 is actually probably enough (I have asked them to look at having 7), because by changing acceleration it smooths out the transitions. For me now, the thinking is that overly long pre-infusion is not such a good thing. Having done lots of experimentation, the shots cease to benefit beyond a certain point because of the fineness of grind issue. I believe there comes a point when an extremely fine grind starts to become undesirable and a puck that has too much water soaked into it at low pressure changes, perhaps becomes unstable?

I intend next to rather than have a pre-infusion stage to try a slow ramp stage. Using the much lower acceleration I have set now... I'm going to try for a 6 bar stage for a few seconds rising to a 12 bar, then 9 then 8, then 6. What I'm looking to try and do is apply the high pressure in a much more progressive way.

My belief about the very fine grind not being beneficial past a certain point, comes from experiences over many years with different machines and both single double and odd sized baskets.

With the sage, I wonder if you would benefit by setting your expansion valve to 12 bar and allowing a higher than 9 bar phase, to try and simulate the profile I used when I first posted this thread. I realise the control won't be easy, but it might be worth a try.


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## Charliej (Feb 25, 2012)

I'll have a look into how easy altering the opv would be, one thing I have found the adjustable preinfusion pressure is useful is that odd variety coffee you sometimes come across that can be an utter pain in the arse to get right grindwise. If I hadn't had the Sage I could have seen myself hitting my head against a brick wall with that german Nordic style roasted coffee I had the other week, as well as wasting 80-90% of it rather than 4 shots or so (none of which were undrinkable in milk oddly enough even the 41g in 15 seconds inc. 5 seconds pre-infusion shot). There are times when making espresso using the Sage is to use Gary's expression like having stabilisers on a bike as kid, sometimes a shot that should by commonly held standards and notions be utterly shite comes out really well.

Also both myself and Gary have played around with pulling an entire shot at around 80% of standard pressure ie 80% of 9 BAR which means you effectively have no preinfusion. I would be curious as to what the Sage could be made to do if you had access to a developers kit and knew how to update the software , even if it meant blowing an eprom to do it, as I suspect it is actually capable of far more than is currently available.


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## Eyedee (Sep 13, 2010)

I may be talking absolute rubbish here (as I often do) but can the concept of pre infusion be directly related to the fact that water always finds the easiest route. Once the grinds are wet they allow the passage of water.????????

Ian


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## DavecUK (Aug 6, 2013)

Eyedee said:


> I may be talking absolute rubbish here (as I often do) but can the concept of pre infusion be directly related to the fact that water always finds the easiest route. Once the grinds are wet they allow the passage of water.????????


Well, they do definitely seem to allow water through faster, the wetter they are before the main extraction pressure gets applied. If you pull a shot a second time through an already used puck, the flow is really fast.....faster than if you simply let a shot run for 50 seconds and measured vs that last 25s

last night I tried what would have effectively been a smooth slow ride up to 12 bar and rather than a 4-5 second preinfusion, then profiled as before....again the shot was very good.


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## Mrboots2u (May 10, 2013)

This machine with an Ek would make an interesting partnering, I am guessing you are not letting it go to Gary unless it out of your cold dead hands.......


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## Charliej (Feb 25, 2012)

Mrboots2u said:


> This machine with an Ek would make an interesting partnering, I am guessing you are not letting it go to Gary unless it out of your cold dead hands.......


I would imagine the Vesuvius would make an interesting partner to any top end grinder.


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## DavecUK (Aug 6, 2013)

Mrboots2u said:


> This machine with an Ek would make an interesting partnering, I am guessing you are not letting it go to Gary unless it out of your cold dead hands.......


Errr....no!

It's proving too useful for me....It allows me to suggest changes to reflect in the final production model. Engineering, finish, software. The stuff I'm discussing with the designer, much of which you will never see, or even know was done (unless I remember to put it in the review. I can also add some bits to see how they perform, before they go into the production models. The dealer machines Rodney has are already different. Not in terms of absolute performance and shot quality, but subtle differences we've already had implemented...its was the reason for the wait for the UK machines as some of the stuff I specified was being implemented.

So I thought I'd better hang on to it....for as long as possible....besides, I made a special place for it in the Kitchen.









Also unlike you guys, I'm not going to mind using the prototype for a long time.....because the coffee it produces is just as good.


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## Spazbarista (Dec 6, 2011)

http://www.bellabarista.co.uk/vesuvius-dual-boiler-espresso-coffee-machine.html?___store=default

Is this the Vesuvius you have Dave?


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## coffeechap (Apr 5, 2012)

Yep that is the one


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## Spazbarista (Dec 6, 2011)

Any idea on price? (Apols if already posted)


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## Mrboots2u (May 10, 2013)

Expobarista said:


> Any idea on price? (Apols if already posted)


Listed on site as available at £2995


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## Spazbarista (Dec 6, 2011)

Fuk dat sheet, mun


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## Daren (Jan 16, 2012)

Expobarista said:


> Fuk dat sheet, mun


Is that street talk for "quite a reasonable price Sir"?


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## Mrboots2u (May 10, 2013)

Dave now you have lived with the machine a bit longer can you comment on how much your using the presets for PP on a day to day basis. Do you have a couple of " go to " pre sets that your using the majority of the time or has it become a variable you adjust like temp and dose depending on the coffee used? Have you used it with a mix of beans or are you predominantly using one currently? Cheers


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## DavecUK (Aug 6, 2013)

Mrboots2u said:


> Dave now you have lived with the machine a bit longer can you comment on how much your using the presets for PP on a day to day basis. Do you have a couple of " go to " pre sets that your using the majority of the time or has it become a variable you adjust like temp and dose depending on the coffee used? Have you used it with a mix of beans or are you predominantly using one currently? Cheers


I've 3 go to presets, well 4 actually.

Flat for comparison testing (I did this when I had the preinfusion chamber enabled)

Long 2 bar infusion, 12 bar, sloping down to, 9 bar, 8 bar, 6 bar

As above, but no infusion

Super long infusion

Trouble is there are so many variables and part of what I'm doing is also testing. I have had pump acceleration at all sorts of different values from stock 2000, to current 180. The 2000 is a bit misleading because acceleration only really comes into effect between about 750 and 0. With differences being apparent in the rate of pressure change at around increments of 20. So lots of granularity to play there. In addition the pump has a set of PID parameters, which can further moderate response.

I'm not aiming so much for a series of pressure "steps" as a smooth transition, so I use the global pump acceleration parameter to achieve this and the PID parameters to further modify this response more if required

*In addition I have been running with the E61 preinfusion valve disabled for a while*, as this is not really required with this advanced type of pressure profiling machine and my current views are this actually improves the performance of the machine and pump....but does require a longer preinfusion phase simply to allow for the extra time for the preinfusion chamber to fill. The charts below show the respective pressure lines for high and low pump acceleration. Of course these are simply examples and an approximation of one of my profiles, but they give the general idea.









Note: having no preinfusion chamber enabled is the case in most solenoid operated E61 groups (they sacrifice the prenfusiion chamber), but of course with this pump in't a non issue, unless pump acceleration is set to max...which personally I feel is never the best setting for the pump. At the moment my go to profile is the one in the second graph, but with time I am sure I will find certain coffees benefiting from different profiles. There are a lot of variable to play with here...*essentially it's down to the old Mark 1 human being to decide the best setup for particular coffees, or at least best for them, which is really key strength of this machine*.

There are a few other surprises to come.

edit: really even these profiles are not quite what is happening, wish I could actually draw the graphs neatly by hand.


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