# E61 vacuum?



## Beemer (Jun 19, 2012)

When, after a pull, a E61 grouphead valve is closed should there be a vacuum effect that sucks excess liquid from the pod?


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## jimbow (Oct 13, 2011)

When you say 'pod' do you mean a pod/capsule like the ESE pods or do you mean the ground coffee puck?

During the pour, a lot of pressure builds up above the puck, created by the pump. When one stops the pour, this excess pressure is released via the solenoid valve (it is actually a mechanical valve on true E61 groups). This sudden release of pressure helps remove excess moisture from the puck and allows the portafilter to be removed from the group without pressurised hot water spraying everywhere (aka portafilter sneeze).


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## Beemer (Jun 19, 2012)

jimbow said:


> When you say 'pod' do you mean a pod/capsule like the ESE pods or do you mean the ground coffee puck?
> 
> During the pour, a lot of pressure builds up above the puck, created by the pump. When one stops the pour, this excess pressure is released via the solenoid valve (it is actually a mechanical valve on true E61 groups). This sudden release of pressure helps remove excess moisture from the puck and allows the portafilter to be removed from the group without pressurised hot water spraying everywhere (aka portafilter sneeze).


Sorry I should have said puck not pod. I asked the question because my Duetto E61 frequently leaves the used pod sodden and the portafilter drips as I carry it to the knockbox. I guess I get 50% dry pucks


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## forzajuve (Feb 2, 2011)

Beemer said:


> Sorry I should have said puck not pod. I asked the question because my Duetto E61 frequently leaves the used pod sodden and the portafilter drips as I carry it to the knockbox. I guess I get 50% dry pucks


How quickly are you knocking out? Its best to leave the puck in between shots for temp stability.


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## SlowRoast (Sep 24, 2010)

What's your dose like? At work we use a 14g dose for doubles - pucks are very rarely dry and solid (tend to just splatter all over the knockbin and the portafilter leaks scalding hot espresso remains all over the baristi's hand), unlike the 21g triple shots or my 18g doubles here at home.

Channelling could be a cause too, but if your dose is low, there's going to be more liquid in the space between the puck and the screen, and I should imagine it can only exhaust so much water out the vent pipe before the pressure is too low to do so. I tried a low dose and got a messy channelled shot and a filthy basket after.


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## Beemer (Jun 19, 2012)

My double dose is never less than 18gm and pressure is 10.5Bar all through the pull. There is no evidence of channelling. Its just a strange thing to see a "dry" puck then on the next soon after pull a soaking wet one.


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## garydyke1 (Mar 9, 2011)

Ive run tests on this on my Brewtus :

VST 18g basket, all pucks knocked out 1 min after shot finished :

16.5g dose - sloppy puck

17g - semi solid puck with some standing water on top

17.5g - semi solid puck

18g - firm puck quite dry

18.5g - solid puck with imprint of showerscreen plain to see.

19g - puck must have expanded and cracked as the shot was three streams of liquid - solid puck which shattered when removed

I was using a coffee which was a medium roast, not exactly dense. Personally would use 17.5g-18g.....which is exactly what the basket is designed for


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## Beemer (Jun 19, 2012)

Interesting report and made me think about the E61 fill process. When the is a dummy pull with no portafilter in place the water does not jet out of the screen. With a loaded portafilter in place we cannot observe what is happening so we assume that the internal pressure builds up as the air is compressed. Water will permeate through the grounds but does it loosen the puck as it does this? If it does then what's the point of tamping? If it does not break it up then full pressure is when the portafilter is full.

My point is that if the puck is loosened during the early fill then perhaps this is why such a puck will be sodden after the pull? The lower the grams the higher the risk of puck loosening which matches your findings.

I see a lot of posts mentioning evidence of channelling but I have never seen it regardless of puck wetness. I tamp with at least 30lb pressure.


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## garydyke1 (Mar 9, 2011)

Beemer said:


> Interesting report and made me think about the E61 fill process. When the is a dummy pull with no portafilter in place the water does not jet out of the screen. With a loaded portafilter in place we cannot observe what is happening so we assume that the internal pressure builds up as the air is compressed. Water will permeate through the grounds* but does it loosen the puck as it does this*? If it does then what's the point of tamping? If it does not break it up then full pressure is when the portafilter is full.
> 
> My point is that if the puck is loosened during the early fill then perhaps this is why such a puck will be sodden after the pull? The lower the grams the higher the risk of puck loosening which matches your findings.
> 
> I see a lot of posts mentioning evidence of channelling but I have never seen it regardless of puck wetness. I tamp with at least 30lb pressure.


Take a shot glass and fill to the top with fresh espresso-grind coffee, then pack the coffee in to compress it about 2/3rds of the way down.

Then pour very hot water from the kettle on top of the grinds.....observe them ''bloom'' and expand exceeding the volume of the shot glass


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