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Discussions > Espresso > Q and A > Channelling...  
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Ludvig
Senior Member


Joined: 13 Apr 2013
Posts: 8
Location: France
Expertise: I love coffee

Espresso: Reneka Single
Grinder: Ascaso Steel I1
Posted Wed Nov 27, 2013, 6:37am
Subject: Channelling [Solved]
 

I have restored an old Reneka Single and I'm finally pulling (half-)drinkable shots on it (grinder is an Ascaso Steel I1, also have a Santos 6a), the problem is that whatever I do, there is channelling.

I have rounded up the usual suspects and don't think they are of concern. Beans (2 days from roasting to about 2 weeks), grinder, distribution, tamping, temperature (flush'n go) and pressure (8-9bar) should be okay.

I have also removed the outsticking part (metal file + some hours^^) of the screw holding the shower screen as it broke the puck otherwise.
Bought a new basket and finally when fiddling enough with grind and dose, I got some headroom (like 1.5-2mm) and the shots are almost drinkable. Too harsh and blonding occurs too fast + channelling.

If I grind coarser the channelling disappears but I get an infamous "15 second" espresso.
If I gring finer it starts out okay but chanelling Always occurs I guess about 10 seconds in to the shot.
Depending on the grind setting, it will produce 60ml in 15 sec or 20ml in 15 sec but what ever I do, at 15 seconds the pour is already completely blond.

The channelling always forms in a ring between the centre and the edge (like a ring with 35mm diameter and 10mm width in the 57mm basket), usually there is one or two holes (at 180 from each others), see photo.



Should I install another showerscreen under the original one to disperse the water flow or something or am I missing something else here?

Thanks!

Ludvig: P1050379.JPG
(Click for larger image)
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calblacksmith
Moderator
calblacksmith
Joined: 25 Nov 2007
Posts: 7,947
Location: Riverside, Ca, U.S.A.
Expertise: I live coffee

Espresso: ECM Vene. A1, La Cimbali M32
Grinder: Azkoyen Capriccio, Major
Vac Pot: 40s era Silex
Drip: Msl. Com. brewers
Roaster: gave it a try, decided no
Posted Wed Nov 27, 2013, 6:43am
Subject: Re: Channelling
 

It is nearly always a result of shot prep. Proper shot prep will eliminate it.
I suspect your grinder may not be up to the task of grinding for espresso. It is not only that it needs to be a fine grind, it needs to be consistent an that is a place that a lot of less expensive grinders fall short.

 
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NobbyR
Senior Member
NobbyR
Joined: 10 Jul 2011
Posts: 2,057
Location: Germany
Expertise: I love coffee

Espresso: Poccino Opus One, Ariete
Grinder: Eureka Mignon Istantaneo
Vac Pot: N/A
Drip: Melitta Linea Unica de Luxe
Roaster: N/A
Posted Wed Nov 27, 2013, 7:35am
Subject: Re: Channelling
 

calblacksmith Said:

I suspect your grinder may not be up to the task of grinding for espresso.

Posted November 27, 2013 link

The Ascaso Steel I-1 is a stainless steel, consumer grade, stepless, flat burr grinder that should be capable of consistently grinding fine enough for espresso. But I agree, channelling is usually a result of shot preparation problems like distribution. For example, tapping the portafilter after tamping (a step that used to be endorsed a while ago) can promote channelling. Can you give us a detailed description of your workflow?

 
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"This drink of the Satan is so delicious that it would be a shame to leave it to the infidels." (Pope Clement VIII on coffee, when he was urged to ban the beverage)
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jwoodyu
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jwoodyu
Joined: 31 Dec 2010
Posts: 857
Location: Michigan
Expertise: I live coffee

Espresso: Allex Duetto II
Grinder: Mazzer Major
Posted Wed Nov 27, 2013, 8:04am
Subject: Re: Channelling
 

That is a rotary pump machine? How much are dosing?

 
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NobbyR
Senior Member
NobbyR
Joined: 10 Jul 2011
Posts: 2,057
Location: Germany
Expertise: I love coffee

Espresso: Poccino Opus One, Ariete
Grinder: Eureka Mignon Istantaneo
Vac Pot: N/A
Drip: Melitta Linea Unica de Luxe
Roaster: N/A
Posted Wed Nov 27, 2013, 8:11am
Subject: Re: Channelling
 

jwoodyu Said:

That is a rotary pump machine?

Posted November 27, 2013 link

As far as I know, Renaka only builds commercial espresso machines, so it should have a rotary pump.

 
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"This drink of the Satan is so delicious that it would be a shame to leave it to the infidels." (Pope Clement VIII on coffee, when he was urged to ban the beverage)
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Ludvig
Senior Member


Joined: 13 Apr 2013
Posts: 8
Location: France
Expertise: I love coffee

Espresso: Reneka Single
Grinder: Ascaso Steel I1
Posted Wed Nov 27, 2013, 9:06am
Subject: Re: Channelling
 

Hi everybody and thanks for the input!

The machine has a classic (new) Ulka vibe pump.

I dose from about 11 to 12.5g, more and there won't be enough headroom (and thus instant channelling). I have tried several techniques of dosing, grinding in a jar fluffing the grinds up with a toothpick, doing a WDT in the PF and grinding directly in the basket + WDT. Never tapping the basket and carefully tamping to not level one side, swift pull out and re-tamp + turn to polish.

I can't just fill the basket up, scrap off and tamp as there will be too much coffee, the group sticks out really much.

Then I flush the machine until all super-heated water gets out the HX plus 1-2 sec (checked with a thermometer-PF, should at least be inside a reasonable range like 90-96C), locks in and pull.

Starts quite black, goes stripy (but thin) and quickly to blond.

So either:
A) I'm messing the preparations and need to get better at that (maybe get a naked PF to help?).
but why is there always this "ring", whatever I do? Maybe there is some other technique I can try?

or
B) maybe there is something with the waterflow.
If I tight (quite hard) the screw that holds the showerscreen, the waterflow is actually blocked, maybe there is a "jet" coming out from somewhere (as I have just tightened the screw "enough")? I thought about this as the screw has 2 holes and the holes in the puck (when there are 2) are 180 separated.
I attached an image of another ruined shot, you can really distinguish the ring(right? the photo doesn't do real justice here) and the hole to the up-right.

Ludvig: P1050385.JPG
(Click for larger image)
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Ludvig
Senior Member


Joined: 13 Apr 2013
Posts: 8
Location: France
Expertise: I love coffee

Espresso: Reneka Single
Grinder: Ascaso Steel I1
Posted Wed Nov 27, 2013, 9:45am
Subject: Re: Channelling
 

Just to clarify a bit about the shower screen and so, this is how the group looks without the shower screen (usually it's a bit cleaner), there are no plate between the group and the screen with (say) 6 holes to help the waterflow EDIT it seems it's called a diffuser disk /EDIT. The outsticking metal also (in my eyes) corresponds quite well to that 'ring' I get.

Ludvig: P1050123_small.jpg
(Click for larger image)
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Ludvig
Senior Member


Joined: 13 Apr 2013
Posts: 8
Location: France
Expertise: I love coffee

Espresso: Reneka Single
Grinder: Ascaso Steel I1
Posted Wed Nov 27, 2013, 11:22am
Subject: Re: Channelling
 

I removed the shower screen and put back the "dispenser-screw" and there is really two distinct jets of water (battery died before I could take a better shot, the water is basically only in those 2 jets).
So if I'm doing my distribution/tamping bad or good, resolving this water jet problem could maybe give me a more forgiving machine / solve my problem?

Ludvig: P1050390_small.jpg
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jwoodyu
Senior Member
jwoodyu
Joined: 31 Dec 2010
Posts: 857
Location: Michigan
Expertise: I live coffee

Espresso: Allex Duetto II
Grinder: Mazzer Major
Posted Wed Nov 27, 2013, 8:29pm
Subject: Re: Channelling
 

I wonder is you have scale or something going above the fuses cause that does not look right

 
Yes i have a reason for leaving SCG off my list, yes it is my opinion, yes it is subjective as opinions are by definition, no don't start a flame war because you disagree.
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Ludvig
Senior Member


Joined: 13 Apr 2013
Posts: 8
Location: France
Expertise: I love coffee

Espresso: Reneka Single
Grinder: Ascaso Steel I1
Posted Thu Nov 28, 2013, 3:18am
Subject: Re: Channelling
 

I have descaled not a long time ago and if I remove the screw, the water flows normally.

I have attached an image of the "screw" and it is those two holes (edit/clarify: there is one on the opposite side of the screw, I'm not talking about the top one, that one is where water enters) that makes the water jets (there is not much room for the water to flow when the screw is in there), and what I assume, my problems.

What do you think about putting something between the group and the shower screen that breaks those jets or should I experiment with another kind of fixation and if so, do you have any ideas?

Ludvig: ERQ11_big.jpg
(Click for larger image)
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