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Discussions > Espresso > Q and A > Channeling: How...  
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hamm
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hamm
Joined: 22 May 2003
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Location: Kettering, Ohio
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Espresso: Alex Duetto (1st gen)
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Posted Wed Jan 28, 2009, 9:11am
Subject: Channeling: How do I solve it?
 

I need a little help here.

Lately my shots have been off kilter and I think I've slipped into a habit of doing something wrong that I'm not aware of.  Here's what's up:

Still have my Isomac Tea and Mazzer mini.  The Tea has had several repairs made over the past year, but it still has the original pump. Most everything else has been replaced or cleaned/fixed.  The Mazzer has had the burrs "cleaned" with Grindz once in the past year, and it probably ground about 36 lbs. of coffee in 2008.  (average for me is about 30 lbs/yr)

Shots now pull at 8 to 8.5 bars, and they rarely hit 9 bars anymore.  9 is where I got my best tasting shots no matter which coffee I've used.

Shots now taste sour.  Currently I've got some Panama La Berlina that was roasted Sunday.  It's already very bright, but I've made great espresso with it before and this time it's like drinking pure citric acid.  I'll leave open that it's the crop for this time of year, or the time it was harvested.

All the spent pucks have spots that signal channeling to me. I've attached a couple pics.

My shot pulling routine:

Grind
Dispense into the double basket so that a small "hill" rises over the lip of the portafilter.
Two solid taps on the counter to settle the coffee.
Top off with another small hill of coffee.
Brush off excess with finger to make a flat surface.
Tamp straight down with even pressure ensuring it's completely level
Remove excess from sides, polish the tamp, lock & load

Sometimes I'll get the tiniest bit of extra coffee... say a gram or so, that will make the shot go either way.  After almost 6 years of doing this though, it seems like the shots are far more finicky than they used to be.  

I'm aware of the random variables, such as temperature/humidity of the room, weather, position of planets, etc.  I just wonder what I might be doing/not doing that's caused me to notice mediocre shots when I used to get great ones.

Thanks in advance for any help

hamm: puck-top.jpg
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hamm
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hamm
Joined: 22 May 2003
Posts: 530
Location: Kettering, Ohio
Expertise: I live coffee

Espresso: Alex Duetto (1st gen)
Grinder: Mazzer Mini
Vac Pot: I'm not that kind of guy...
Drip: From the faucet occasionally
Roaster: I buy from several
Posted Wed Jan 28, 2009, 9:12am
Subject: Re: Channeling: How do I solve it?
 

Another 'shot' (pun intended)

hamm: puck-side 1.jpg
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hamm
Senior Member
hamm
Joined: 22 May 2003
Posts: 530
Location: Kettering, Ohio
Expertise: I live coffee

Espresso: Alex Duetto (1st gen)
Grinder: Mazzer Mini
Vac Pot: I'm not that kind of guy...
Drip: From the faucet occasionally
Roaster: I buy from several
Posted Wed Jan 28, 2009, 9:12am
Subject: Re: Channeling: How do I solve it?
 

One more

hamm: puck-side 2.jpg
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dana_leighton
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dana_leighton
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Posted Wed Jan 28, 2009, 10:42am
Subject: Re: Channeling: How do I solve it?
 

A couple of observations:

hamm Said:

The Mazzer has had the burrs "cleaned" with Grindz once in the past year

Posted January 28, 2009 link

My routine is to clean every month by disassembling my grinder. I grind only about 6 lb per month. Perhaps excessive, but I am thinking once a year with Grindz is a bit too infrequent. That alone though would not cause sour shots and/or channeling.

Shots now pull at 8 to 8.5 bars, and they rarely hit 9 bars anymore.

No matter how fine your grind is? Do you go from 8 bars to choke?

Shots now taste sour.

The classic cause of sour shots is low brew temp. Have you measured the temperature of the brew water? Styrofoam cup method would be sufficient for this exercise.

All the spent pucks have spots that signal channeling to me. I've attached a couple pics.

Most geeks think puck postmortem is not very informative. To see channeling occuring, you'd be best to observe the pour with a bottomless PF.

My shot pulling routine:
...
Two solid taps on the counter to settle the coffee.
...
Tamp straight down with even pressure ensuring it's completely level

You may think about not settling with the counter taps. dose into the PF, distribute with a straight edge or your finger, tamp lightly (about 5 lbs), then use either (a) a tap on the side of the PF with the tamper or (b) an angled light tamp on "north, south, east, west" (both of these methods are to get the remaining coffee off the side of the PF), then tamp at 30 or more lbs.

Again though, improper distribution or tamping itself will not cause sour shots. It might cause chanelling or uneven extraction, but in either case you'll be overextracting, which typically results in bitter shots, not sour.

 
Dana Leighton - Espresso hack and CoffeeGeek moderator
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mrgnomer
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mrgnomer
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Posted Wed Jan 28, 2009, 12:24pm
Subject: Re: Channeling: How do I solve it?
 

I agree that sour shots is commonly attributed to low brew temps.  Could be the greens as well, as you suppose.

Was your machine recently descaled?  There might be some descaler still in the HX line if so.  Or, if you use boiler water for Americanos it could be in the boiler.

Could be your barista habits as well.  Your routine with settling the grinds, topping them off and then levelling off sounds like you'd be prone to overdosing.  I've found my Vetrano prefers an underdose.  She doesn't do well with an overdose.  I agree, then, that you might try levelling off without topping off again.  That or try underdosing.  Use a Stockfleth's move or something to level off and distribute under the lip of the basket with an underdose.

It's hard to see signs of channelling in the pictures.  Are you getting thin, light, fast pours?

Chanelling could come from a wet basket if it's underdosed a bit and lifts out during extraction.

You could try changing things up and experimenting.  Sometimes, for me, if extractions are going funny I try to change up my technique.  For example;  if you've got more than one tamper, try changing the tamper.  If you tap the side of the basket before a final tamp and polish, try it without the tap.  If you usually do a NSEW tamp, try a nutating tamp.  Try a flush and go if you normally flush and wait for a rebound.  Try grinding finer and tamping lighter.  Try coarser and harder.  Let some beans rest past 10 days and try them out.  Do a S.O. roast of a good quality robusta and try a blending a pinch in to see what happens to the extraction quality.

This has just come to mind but is your HX still running hot after the machine heats up?  My now 3 year old Vetrano's HX doesn't always stay superheated.  I know this because sometimes I get no water dance and her nose is cooler to the touch.   I have to flush now and then to get her going.  I'm thinking the thermosyphon loop gets stalled but I don't know by what if it is.  Could be air, could be scale although I agressively descale about twice a year.  If sour shots are because of too low brew temps something is lowering the HX temp.  If not the thermosyphon, maybe the boiler pressure is low.
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hamm
Senior Member
hamm
Joined: 22 May 2003
Posts: 530
Location: Kettering, Ohio
Expertise: I live coffee

Espresso: Alex Duetto (1st gen)
Grinder: Mazzer Mini
Vac Pot: I'm not that kind of guy...
Drip: From the faucet occasionally
Roaster: I buy from several
Posted Wed Jan 28, 2009, 7:36pm
Subject: Re: Channeling: How do I solve it?
 

Hey guys, thanks for the responses.  You gave me a lot of information based on what I gave and I realy appreciate it.

On the water temp.  I thought that myself but I wonder how to get the temp to increase should that be the case.  I don;t think I have a very good thermometer because it's always read around 195-200 F even when I can tell by touch that the temps are different.  I could swear it's running cooler than that now though.  I adjusted the pressure stat to get it to cycle between 1.3-1.5 bars.

It's had the heater replaced and a full descale, but that was last summer and I've done plenty of good shots since then.

Chris at Chris' Coffee told me once that a Mazzer needs about 300 lbs of coffee run through it before it really needs to be taken apart.  I guess to each his own there.  I clean mine out with a small brush after every grinding but I'm sure there will always be residue left behind. Occasionally I'll stick the end of the vacuum hose to clean out the doser.

To answer a few more of your points, yeah, I'll go from 8 to 8.5 bars to a full blown choke, but even then it'll only go up to about 9.5 or so.  When I backflush, it only goes up to about 9.9 to 10 bars. I thought it used to go higher than that when the machine was newer.  The best looking streams/shot pulls with great crema and color are the ones pulling in about 18-20 seconds, about 1.5-2 oz in volume. But those taste a bit sour. The shots that pull longer than 30 seconds tend to be thick and syrupy, but are still sour, not bitter like an overextraction.

I'm definitely going to try to go with less coffee volume and a different approach to tamping since those are the variables most controllable to me. I'll post back here if that helps anything.

Incidentally, I'm hoping that a lot of this is due to the coffee I'm using.  It's very fresh, but a single origin.  NOT the easiest stuff to pull espresso with!  Last summer after the machine overhaul I had some of the same Panama La Berlina that pulled the only God sots I've ever had. It was stunning to the point where I got this batch thinking I could come close.  it's amazing how 6 months later a crop can change, or more likely, my skills have worsened!

Thanks again fellas,

Hamm
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hamm
Senior Member
hamm
Joined: 22 May 2003
Posts: 530
Location: Kettering, Ohio
Expertise: I live coffee

Espresso: Alex Duetto (1st gen)
Grinder: Mazzer Mini
Vac Pot: I'm not that kind of guy...
Drip: From the faucet occasionally
Roaster: I buy from several
Posted Wed Jan 28, 2009, 7:51pm
Subject: Re: Channeling: How do I solve it?
 

OK,

I checked the brew temp. Straight out of the e-61 with no pre-flush, my new digital thermometer read as high as 197 F but hovered more around 195-196.

I dosed and tamped along the lines mentioned above and...

The shot pulled at 9 bars, but it choked the machine still.  I let it run for 35 seconds, but I only had espresso dripping for about 25 of those.

The shot came in around 1 oz, what I'd call a ristretto.  The taste?  Roughly the same.  It was good, but still sour.  

I'm going to assume for now that I'm trying to critique my shot pulling with some very difficult coffee.  But at least I have some good info to go on or a bit.

Thanks once again.

Hamm
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dana_leighton
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dana_leighton
Joined: 11 Jan 2002
Posts: 1,914
Location: Little Rock, AR
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Espresso: Isomac Relax; Caferina...
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Posted Wed Jan 28, 2009, 8:44pm
Subject: Re: Channeling: How do I solve it?
 

hamm Said:

I checked the brew temp. Straight out of the e-61 with no pre-flush, my new digital thermometer read as high as 197 F but hovered more around 195-196.

Posted January 28, 2009 link

With no cooling flush? The cooling flush water should be over 212! Even if it was after the cooling flush, that is quite cool, for most coffees. Lengthen your wait time after the cooling flush so that your brewing temperature is 198-200. If you can't get that temperature after a wait, you need to adjust the pressurestat to change the boiler temperature.

 
Dana Leighton - Espresso hack and CoffeeGeek moderator
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hamm
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hamm
Joined: 22 May 2003
Posts: 530
Location: Kettering, Ohio
Expertise: I live coffee

Espresso: Alex Duetto (1st gen)
Grinder: Mazzer Mini
Vac Pot: I'm not that kind of guy...
Drip: From the faucet occasionally
Roaster: I buy from several
Posted Sun Feb 1, 2009, 12:19pm
Subject: Re: Channeling: How do I solve it?
 

dana_leighton Said:

With no cooling flush? The cooling flush water should be over 212! Even if it was after the cooling flush, that is quite cool, for most coffees. Lengthen your wait time after the cooling flush so that your brewing temperature is 198-200. If you can't get that temperature after a wait, you need to adjust the pressurestat to change the boiler temperature.

Posted January 28, 2009 link


Thanks, Dana.

Yeah, that was without a cooling flush.  Ever since day 1 I always run about 4-6 oz of water (until it stops spurting) then pull the shots.  For  long time the shots were fine.  I'd say after the initial learning curve, I've gotten great results about 85-90% of the time.  Only recently it dawned on me that something isn;t quite right.

Last summer when I replaced the heating element? I never tweaked the pressure stat.  When I noticed the shots pulling under 9 bars, I adjusted the stat so the heater comes on at 1.3 and goes off at 1.5  Should I go higher?

My instincts say that without the cooling flush, the water should definitely be around the boiling point.  So I'll focus on trying to get it hotter for now.

Is there any special trick to getting the P'stat adjusted correctly?  I have a Jaeger and all I did was give a tiny twist to the '+' side to get it to go up to where it's at now. Is there a point that's considered too high?

Thanks again!

Hamm
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dana_leighton
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dana_leighton
Joined: 11 Jan 2002
Posts: 1,914
Location: Little Rock, AR
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Espresso: Isomac Relax; Caferina...
Grinder: Macap MXK; Baratza Vario-W;...
Vac Pot: Yama 5-cup
Drip: Technivorm; CCD; Melitta
Roaster: Poppery I w/PID controller
Posted Sun Feb 1, 2009, 12:49pm
Subject: Re: Channeling: How do I solve it?
 

hamm Said:

Yeah, that was without a cooling flush.  Ever since day 1 I always run about 4-6 oz of water (until it stops spurting) then pull the shots.  For  long time the shots were fine.

Posted February 1, 2009 link

Immediately after the cooling flush, the brew water should be too cool -- For most HX machines, you need to wait 10-30 seconds after a full cooling flush for the brew temperature to come back up to 200 or whatever temperature you use.

Why are you measuring water temperature prior to the cooling flush?!? You want to target the temperature at the point of brewing, not at the cooling flush. Do a cooling flush, then wait n seconds and pull water to measure temperature. Increase n by whatever factor you use. For example try 10 seconds, and if that's too hot, wait another 5 seconds, and repeat.

Last summer when I replaced the heating element? I never tweaked the pressure stat.  When I noticed the shots pulling under 9 bars, I adjusted the stat so the heater comes on at 1.3 and goes off at 1.5  Should I go higher?

The boiler pressure does not affect the brewing pressure. The brew water is a closed circuit from the pump, through a pipe immersed in the boiler water, then to the group head. Increasing boiler pressure via the pstat will NOT change the number of bars indicated on the brew pressure gauge -- only adjusting the OPV will! Have you tried adjusting the OPV yet? Adjusting the pstat only affects the temperature.

Is there a point that's considered too high?

I am not an engineer, so I am not sure about that. Most home machines I have used and seen have the boiler pressure at .9 to 1.2 -- 1.3-1.5 is getting a bit high. You'll know it's too high when the safety valve blows off steam, but I would not want to push it too much higher than you have it. If the temperature is still too low, I suspect other problems than the boiler pressure being too low.

You have 2 separate problems here:
(1) brew pressure too low
(2) cool brew temperature

My next step for (1) would be a descale. I descale quarterly, because my 6-month descaling routine wound up being too infrequent, and I had to spend $400 to have it professionally descaled and parts replaced. If I had to guess, I suspect the group head may have lots of scale built up, restricting the flow at the group.

Another possibility for (2) is that the boiler temperature probe is inserted too deeply, so that the HX pipe may not be fully submerged. Try pulling the temperature probe up an inch or so. Do this while the machine is off and cool, in case you accidently pull it all the way out. If the probe is too high, you'll get weak steam, and water will come out of the pressure relief valve.

Good luck. If you get frustrated with it, pack it up and send it off to my favorite tech - Stefano at EspressoCare.

 
Dana Leighton - Espresso hack and CoffeeGeek moderator
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