# The Lever Effect



## doolallysquiff (Jul 26, 2014)

Ok, so I've been playing around with the pre infusion settings on the DB for a while now. My machine is set around the 10 bar mark. To get 9 bar I set the pre infusion to around 90% throughout the entire shot. This seems to work well and the pressure remains fairly constant. I then started going a little lower. At around 80-85% I'm around 8.5 bar; however, around 15 secs in the shot the pressure slowly declines. Any thoughts?


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## 7877 (Aug 14, 2014)

I'm sorry that makes no sense to me whatsoever. You can set the preinfusion for a certain time and set the power, but the manual is not clear on what the units of that setting are, it recommends 50-65. I've left this at default but pretty sure it's not a % of the normal 9bar full pressure pour....so what do you mean by "I set the preinfusion to around 90% throughout the entire shot?"


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## doolallysquiff (Jul 26, 2014)

I was guessing the pre-infusion setting which you mention is percentage of full pressure. It goes all the way up to 100. So, to reduce the pressure (which reads around 10 bar) I set the pre infusion to run through the entire shot (30 secs). So when I set the pre infusion to 90 or 90% or whatever the unit is for 30 secs, it gives me 9 bar throughout the shot. However, when I lower the pre-infusion to around 80, it gives me just aout 8 bar for the first 10-15 secs then the pressure gradually declines to around 6-7 bar. Hope this makes some sort of sense.


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## jlarkin (Apr 26, 2015)

Hi doolally, is it just because the puck is offering less resistance? If you have a blank maybe you could try the same routine with that (assuming you can do them backfkushes with this machine) and you'll see if it's the machine dropping it towards the end?


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## Mrboots2u (May 10, 2013)

jlarkin said:


> Hi doolally, is it just because the puck is offering less resistance? If you have a blank maybe you could try the same routine with that (assuming you can do them backfkushes with this machine) and you'll see if it's the machine dropping it towards the end?


Probably this . Difference between some pumps and gear inside espresso machines . The V reacts to puck resistance and feedback a pressure during a shot ( I think )


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## doolallysquiff (Jul 26, 2014)

Mrboots2u said:


> Probably this . Difference between some pumps and gear inside espresso machines . The V reacts to puck resistance and feedback a pressure during a shot ( I think )


The V? The puck resistance is the most logical explanation. @jlarkin I back flush at the same setting and you're correct that the pressure remains constant, which proves the resistance theory. But why would the pressure not drop when I'm running a shot at 95 or full pressure throughout the shot i.e. No pre-infusion just a constant 10-bar for 30 seconds?


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## Mrboots2u (May 10, 2013)

doolallysquiff said:


> The V? The puck resistance is the most logical explanation. @jlarkin I back flush at the same setting and you're correct that the pressure remains constant, which proves the resistance theory. But why would the pressure not drop when I'm running a shot at 95 or full pressure throughout the shot i.e. No pre-infusion just a constant 10-bar for 30 seconds?


Apologies - i was on the bus typing that reply , and i can't type or spell, so i abbreviated...

V = vesuvius espresso machine


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## jlarkin (Apr 26, 2015)

doolallysquiff said:


> The V? The puck resistance is the most logical explanation. @jlarkin I back flush at the same setting and you're correct that the pressure remains constant, which proves the resistance theory. But why would the pressure not drop when I'm running a shot at 95 or full pressure throughout the shot i.e. No pre-infusion just a constant 10-bar for 30 seconds?


Darn see Boots beat me to it but as I'd typed so much: The V is MrBoots dirty secret, he keeps it quiet because he wants people to think it's all about the beanses (just kidding, it's the Vesuvius ambient espresso machine, I believe).

I'm not sure, puck and flow behaviour is both something I'm still learning about and also as far as I've seen, less investigated. I'm starting reading the professional Baristas handbook (Scott Rao), if you're genuinely interested in getting deeper it seems like the kind of book that would help...


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## Mrboots2u (May 10, 2013)

Pocket science only here , no proof , just observation ...

Lower pressure > allows to adjust to coarser grind ( more uniform-less micro channeling ) > adjusts flow rate > more contact time

Subjectively does " things " to mouthfeel and clarity...

Really helpful with lighter roasted coffee's on The Ek43 where sometimes with original burrs you can be right on the edge for some " filter roasts " . Allows to sweet shots ..The few shots I've refracted recently , show with the right coffee , it allows long brew ratios ( 1:3 ) keeping espresso like strength , and taste good ( caveat to me only )

I really don't know enough on how the Vesuvius pump works , so we need @DaveC . I am guessing there is something in there that feedbacks pressure and to the brain and pump and then the pump reacts????? Dave please correct me if I am way off the mark


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## doolallysquiff (Jul 26, 2014)

Thanks for the feedback guys. I find this stuff really interesting. If only I had a refractometer to help guide the way - one day. I get the 'allowing long brew ratios & espresso strength' you're talking about, that's why I reduced the pressure in the first instance. I found at full whack the flow rate was too fast around the middle to latter end of the shot. Funny thing though, I just switched to a VST 15g this morning and the shot was a bit of a gusher, yet the tasting notes were more prominent.


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## Mrboots2u (May 10, 2013)

doolallysquiff said:


> Thanks for the feedback guys. I find this stuff really interesting. If only I had a refractometer to help guide the way - one day. I get the 'allowing long brew ratios & espresso strength' you're talking about, that's why I reduced the pressure in the first instance. I found at full whack the flow rate was too fast around the middle to latter end of the shot. Funny thing though, I just switched to a VST 15g this morning and the shot was a bit of a gusher, yet the tasting notes were more prominent.


A refractometer will help you measure and adjust , wont help you taste , gives you a place on a map to choose which direction to go in..

You can use your own senses , in terms of judging mouthfeel , and strength , and ultimately tastyness..

Re the coffee from this morning - where the notes aroudn the fruit acidic side by any chance ...


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## doolallysquiff (Jul 26, 2014)

Mrboots2u said:


> A refractometer will help you measure and adjust , wont help you taste , gives you a place on a map to choose which direction to go in..
> 
> You can use your own senses , in terms of judging mouthfeel , and strength , and ultimately tastyness..
> 
> Re the coffee from this morning - where the notes aroudn the fruit acidic side by any chance ...


yes but also salty.


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## doolallysquiff (Jul 26, 2014)

@Mrboots2u I took the shot a little longer this morning 15>36 in 28 secs. Started at 8 bar and slowly declined to around 6.5 - 7ish. It wasn't too bad but a tad on the bitter side to begin with, more fruit towards the end but a little masked. Going to try 32 out next time. I'm on the the Indian Seethargundu from rave.


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## MWJB (Feb 28, 2012)

Why not try a little longer still, I'd be more concerned about bitterness at the end of the shot than the beginning.


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## doolallysquiff (Jul 26, 2014)

@MWJB Any chance you could elaborate? Not quite following.


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## MWJB (Feb 28, 2012)

The latest issue from the PF has less fats in it & tends to settle at the bottom of the cup, if you are over-extracting, this is where you are most likely to taste it in borderline cases, bitterness at the start is less likely to be over-extraction. If you are starting to get fruit/sweetness towards the end, pull a little longer as you are likely just getting into the tasty zone.


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## doolallysquiff (Jul 26, 2014)

Makes sense, thanks. I was going by the Perger method when once you get to bitterness extract a little less. So, going by your theory, I will pull the next shot a little longer to see if I get more fruit/sweetness. Also, to keep the ratio where it is without diluting any further would grinding a tad finer have a similar effect?


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## MWJB (Feb 28, 2012)

Yes, grinding finer will push up extraction at the current ratio...until you hit a point where it starts to drop off again.


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