Persistent Channeling

[java man]

Most of the shots on my new mini are channeling and spraying little jets and spurts of espresso out of my bottomless PF.

The brew pressure gauge reads 9 bars during the shot. I'm using a new La Cimbali Max Hybrid, and getting ~ 30 second 1.75 oz. pulls.

I grind and dose at the same time, getting a centred pile of grinds that reaches the top edge of the PF. I make sure it covers the entire PF and smooth it off with my finger to leave a slightly domed pile.

I tamp quite hard with the rattleware tamper that came with the machine. It's a good fit in the PF, but is a flat tamper, which I'm not used to. I previously used a Reg Barber convex since ~ 2003.

I seldom had channeling problems on my previous machines (Wega Lyra rotary, La Cimbali M27, Silvia) but this is the first machine on which I've used the La Cimbali Max Hybrid grinder.

I am not an inexperienced newbie -- I've been making ~ 3 shots a day for 17 years, and have never had such consistent problems. But I got my Mini-V, the La Cimbali and the Rattleware tamper at the same time, leaving 3 variables here. Add a 4th variable because the La Cimbali lends itself to grinding and dosing simultaneously, whereas I previously ground, dosed into a scoop, then dumped the grinds into my PF. To my eye, grinding and dosing simultaneously results in better distribution than the "dose and dump" method I was using previously, but who knows?

Does anyone have any suggestions for how I might overcome this annoying problem?

Cheers,

[JohnB]

You didn't mention what you are using for coffee or how fresh it was??

[java man]

I've been using a variety of blends, all quite fresh. Those in my region will recognize the names -- 49th Parallel's house espresso, and JJ Beans Espresso Nero are what I usually use. I get them generally within a few days of roasting.

[SwingT]

I wasn't having channeling really bad - but when I started doing a nutating tamp, that removed the last of it.

with a double basket - 14 grams to 14.5 grams of five day after roast coffee -

I put in 70-80%, tap it to settle, put in the rest, tap and settle again.

level the coffee with the palm of my hand (doesn't do much, the coffee is not up to the rim)

Then do a firm nutating tamp, rotating the tamper in a circle that continues to get smaller, finish up and keep it level by feeling the sides of the portafilter/tamper edges with your fingers - heh, kinda quick, that PF is hot and do an easy twist of the tamper.

Working really well for me, I'm probably not tamping more than 8 to ten pounds. I'm doing most of the tamp with my fingers while making sure the tamper is level

I did have poor results with beans from one roaster, things smoothed out the last bit when I changed to counter culture coffee.

The above procedure pretty much does away with channeling and only gets a small spritzer now and then. Maybe you guys can do it and never even have a quick short spritzer - I'm new at this and am glad I've got it down this good

ETA - I am using a convex base tamper, I think that helps with the Vivaldi - because of the nut hanging down from the screen, gives more space to keep the nut from causing the puck to fracture. It's a bumper convex that Mary at Chris's recommended for use with the machine.

I _am_ an inexperienced newbie, so if it's working for me, maybe it'll be a help to you

[JohnB]

Some of it might be the new burrs in your grinder "breaking in" but you might try a more hands off approach to dosing. I find that the more I play with the grounds in the basket the worse things get. Forget smoothing off the top of the pile; just dose a nice centered pile & tamp. Also back off on the "really hard" tamp as it isn't necessary. I do a light nutating tamp & then finish with a firm centered push in the 10-15lb range.

[java man]

Thanks, I'll try setting the grind finer and reducing the tamping pressure to see what happens.

[java man]

I've tried a few things -- finer grind with light tamp, no fuss dosing, etc. But the only thing that seems to work consistently is putting more coffee in the PF.

My scales are in a box in storage under a mountain of stuff, so I can't say how much I was dosing previously, and what I'm dosing now. But previously, after tamping, the top of the coffee in the PF was a few mm below the line around the inside of the PF. Was I underdosing?

Lately I've tried dosing more, and I can tell that the coffee touches the dispersion screen when I lock the PF in before the shot. This always seemed like over-dosing to me, but it seems to work on the La Spaz???

Where does the top of your coffee come to, after tamping, in relation to the line in the PF?

Thanks,

[JohnB]

Depends on the dose!! I dose anywhere from 14g-21g & don't have persistent channeling once the grind is dialed in. Did your Mini come with the pre infusion chamber installed?

[BrewHaHa]

Lately I've tried dosing more, and I can tell that the coffee touches the dispersion screen when I lock the PF in before the shot. This always seemed like over-dosing to me, but it seems to work on the La Spaz???

If you lock in the full PF, then remove it (before pulling the shot) and see that grounds have come in contact with the screen, you've overdosed. It's arguably OK for there to be a slight impression from the screen bolt/screw, but you'd probably be safer backing off your dose enough so that the grounds touch nothing when locked in. It's OK if, after you pull the shot, you see that the grounds swelled up and contacted the screen. That's typical when the basket is close to full. But if the grounds contact the screen while locking in, the top of the puck will be disturbed - possibly enough to cause channeling.

[RapidCoffee]

Where does the top of your coffee come to, after tamping, in relation to the line in the PF?

Hi Rick. I usually dose 15-16g in the Spaz double basket, but even 17-18g tamps down below the ridge line (in the basket, not the PF). There's a pic of a 17.5g dose here. In general, I find that lower doses (not higher) are more resistant to channeling.

You've eliminated high brew pressure, stale coffee, and an inadequate grinder as potential sources of channeling. The next thing to consider is puck preparation. I'd suggest you pay careful attention to both dosing and distribution. Keep your doses moderate and (this may provoke an outburst from some of the s1cafe regulars ) consider the WDT to avoid distribution problems. A nutating tamp may help to correct minor distribution errors, but the WDT renders it superfluous. Tamp pressure and piston shape are minor issues.

I routinely use a bottomless PF on my Spaz S1, and have no problems with channeling. Despite a rotary pump and no preinfusion, I get consistently good pours with heavy or light tamps, convex or flat pistons, straight or nutating tamps. The biggest factors for me are fresh coffee, an ubergrinder, and meticulous puck prep.

[JohnB]

I routinely use a bottomless PF on my Spaz S1, and have no problems with channeling. Despite a rotary pump and no preinfusion, I get consistently good pours with heavy or light tamps, convex or flat pistons, straight or nutating tamps. The biggest factors for me are fresh coffee, an ubergrinder, and meticulous puck prep.

Are you telling us that you need to use the/your WDT even when grinding with a Robur?? Maybe you got a pair of those bum burrs also? The biggest factors for me are fresh coffee, a lowly Major & leaving the grounds alone.

[RapidCoffee]

Need? No. But it's part of my espresso routine, takes negligible extra time and effort (probably saves me time by keeping grinds in the basket rather than on the counter), and almost certainly contributes to the consistency of my pours. Yes, even with the Robur.

I know you're not a fan, and I'm not recommending it to you. But in Rick's case, uneven distribution could be the cause of channeling, and the WDT is worth a try.

[JohnB]

Need? No. But it's part of my espresso routine, takes negligible extra time and effort (probably saves me time by keeping grinds in the basket rather than on the counter), and almost certainly contributes to the consistency of my pours. Yes, even with the Robur.

I know you're not a fan, and I'm not recommending it to you. But in Rick's case, uneven distribution could be the cause of channeling, and the WDT is worth a try.

I'm not a fan now because I've found it totally unnecessary with my current equipment. I did use it back when I had my Macap M4 & I continued to do the same when I first got my Super Jolly. Initially I was very disappointed with the pours I was getting with the SJ as no matter how much I stirred or leveled I still got channeling & spritzers. One day I tried just dosing a pile into the basket with no stirring or leveling & tamped. Bingo! I now had the beautiful centered pours I had expected from the SJ with no channeling as long as I had the grind dialed in. Same deal with the Major & I have tried grooming several times just to check & every time it screwed up the pour. From my experience with the SJ & Majors (with dosers) I'd have to say that the grinds are as close to perfection as they are going to get (with flat burrs) when they hit the basket & messing with them does more damage then good.

Granted that may not be the case with the Max Hybrid & the WDT is worth a try but if that soves the problem I'd be very disappointed in the M/H if it were my grinder. Considering what good used SJs & Majors can be bought for these days a $750-$800 grinder w/doser that NEEDS the WDT to get good pours is not worth the price you paid.

John - Just out of curiosity have you tried just dosing & tamping with the Robur to see what you get?

[RapidCoffee]

John - Just out of curiosity have you tried just dosing & tamping with the Robur to see what you get?

Sure, I can get good pours without the WDT. But I like the consistency and convenience it brings.

Perhaps the more interesting question is: given your very high-end gear, why does grooming always screw up your pours? Why would stirring or leveling create problems?

[JohnB]

Perhaps the more interesting question is: given your very high-end gear, why does grooming always screw up your pours? Why would stirring or leveling create problems?

Beats the hell out of me, but why should I care?? Thats like me asking you why the heck you feel the need to groom your grounds when you claim they don't need it. If I can do it with a Major you should be able to get consistantly good pours without the grooming. Why do extra work thats not required?

[java man]

Did your Mini come with the pre infusion chamber installed?

Yep.

And given that I got consistently good pours with a MACAP M4 and a Wega Rotary before installing a relay to mimick pre-infusion, I'm less inclined to think my dosing and tamping skills are the cause of the current problem. I'm going to back off the pump pressure on Sunday to see what happens. It's currently at 9.25 bars on some shots, and I'd like to see what happens when I take it down to 8.5. It's possible that my brew pressure gauge reads a little high. Perhaps I DO have a pressure problem that is being masked by a faulty pressure gauge?

Cheers,

[RapidCoffee]

Perhaps I DO have a pressure problem that is being masked by a faulty pressure gauge?

That's certainly a possibility. My S1 (which I bought used) came with the pressure set to 11 bars. The channeling went away when I dropped it to 9 bars, as measured with a DIY PF gauge. Hope that solves the problem for you too.

Beats the hell out of me, but why should I care?? Thats like me asking you why the heck you feel the need to groom your grounds when you claim they don't need it. If I can do it with a Major you should be able to get consistantly good pours without the grooming. Why do extra work thats not required?

I also have a Major, and it's a terrific grinder - certainly the best flat burr grinder I've ever used. At this level of gear, it should be easy to obtain great pours with ease and consistency. I'm curious why your setup is so sensitive to minor changes, such as leveling the grounds. My setup is not.

(FWIW, the WDT does not require extra work. It saves me time and effort by keeping the grinds in the basket (rather than on the counter). That's my last comment on this B-O-R-I-N-G subject. )

[JohnB]

I also have a Major, and it's a terrific grinder - certainly the best flat burr grinder I've ever used. At this level of gear, it should be easy to obtain great pours with ease and consistency. I'm curious why your setup is so sensitive to minor changes, such as leveling the grounds. My setup is not.

(FWIW, the WDT does not require extra work. It saves me time and effort by keeping the grinds in the basket (rather than on the counter). That's my last comment on this B-O-R-I-N-G subject. )

If I recall correctly your Major has the bag spout in place of the doser so the WDT might be useful in your situation. When I dose in my normal range (14-16g) I end up with a nice pile in the center of my basket so no mess, no clumps & no need to stir it down. If I was pushing the limit of the double basket stirring might help or it might just push more grounds over the side.

My theory on why playing with the grounds is a negative in my case is as follows: When the perfectly(by flat burr standards) ground coffee falls out of the Major's doser & hits my basket it has achieved Espresso grounds nirvana so any attempt I make to improve on this can only be met with failure. Looks like I am doomed to a life of effortless centered pours with my Major, at least until CC puts the K10 WBC on sale, then the Major may have a counter mate.

Now back on topic:

Drop the pressure & see what happens but I think you really need to get the scale out of storage so you know how much is in the basket. You might also consider removing the p/i chamber to see if you notice a difference.

[java man]

I believe I have found the problem. It looks like the OPV was sticking.

This morning I reduced the setting on the OPV to a vibration range of 7.5 to 8.5 bars, then prepared and pulled a shot. The brew pressure gauge ramped up as usual for a machine retrofitted with the pre-infusion chamber. The gauge needle reached a point where it vibrated at between 8.25 and 9.25. Normally, at this point I would have stopped watching the gauge. But I kept watching, and after ~ 5 seconds in this range, it moved up to 11 bars.

I cleaned the PF and grouphead and ran a few backflushes. The brew pressure gauge ramped up normally and vibrated between 8 and 9 bars, then after 5 to 10 seconds, increased to ~ 11 bars. This happened on each backflush.

So I reduced the OPV setting again and prepped another shot.

This time, when the brew pressure gauge ramped up to 11 bars, there was a muted "pop", and the gauge needle dropped to 7 bars for the duration of the shot. Water began seeping out of the machine, and when I pulled the drip tray to inspect, I noticed that the exhaust tube on the end of the OPV had popped off. There was no clamp anywhere to be found, so I assume this is a push fit, and should never be under pressure. I was able to replace it without tools.

I dried out the machine and pulled another shot. The pressure gauge ramped up to 8 bars and stayed for the duration of the shot. The needle was not rock-steady, but it vibrated much less than previously. I pulled several more shots, all with the same improved result. Finally, I adjusted the pressure back up to a hair below 9 bars and pulled two more shots. The OPV seemed to work smoothly each time.

I prepped each of these shots "carelessly", grinding and dosing simultaneously, then tamping lightly without redistribution or leveling. There were no signs of channeling in any of the shots.

The history of the machine may provide a clue. I bought the machine in June from a Canadian company that buys wholesale from Chris Coffee. I used it for 3 weeks in June/July, then left the country for 2.5 months while the machine sat in storage. I got it out of storage and started using it again about 10 days ago. Perhaps the OPV was stuck from sitting?

Anyway, it seems to be OK now. Thanks, all for your suggestions.

[SwingT]

OK - I got the bottomless portafilter out again -

Had a couple of short quick spritzers, no channeling - added back a firm probably 20 lb tamp.

Pulled the first shot I have ever had that didn't even have the tiniest short spritzer.

I am weighing usually 14.7 grams - between 14.2 and 14.7, I don't add or take any out.

FWIW, the convex bumber tamper that I have - has a curve that just eyeballing it seems to be at least half the thickness of the nut/bolt that hangs down below the screen - so I'm guessing it helps in terms of not contacting the coffee - plus, that much curve may be somewhat of a help with the nutating tamp, possibly making it more effective.

Tried a number of versions of WDT, didn't have a dissecting needle - used paper clips, various items - went nuts trying to get rid of channeling, major spritzers - however, I'm so newbie that perhaps I was screwing something else up, but never got rid of channeling until I did the nutating tamp, finishing it off by leveling with my fingers on the edge of the tamper/portafilter rim - ( as posted above )

More info - I am running 4 seconds pre-infusion at 32 lbs line pressure.

ETA - since the coffee is below the top of the PF, it may be harder to ensure the tamp is level - a local barista showed me that tip about checking how level the tamp is with your fingers along the edge of the tamper/PF rim. Not sure if that is part of the success I'm having or not

[JohnB]

I prepped each of these shots "carelessly", grinding and dosing simultaneously, then tamping lightly without redistribution or leveling. There were no signs of channeling in any of the shots.

The history of the machine may provide a clue. I bought the machine in June from a Canadian company that buys wholesale from Chris Coffee. I used it for 3 weeks in June/July, then left the country for 2.5 months while the machine sat in storage. I got it out of storage and started using it again about 10 days ago. Perhaps the OPV was stuck from sitting?

Anyway, it seems to be OK now. Thanks, all for your suggestions.

Glad to hear you've gotten the issue sorted out. Have you ever done a detergent backflush or just the plain water b/fs? 3-4 weeks is about the time you would normally do the detergent cleaning, if you put the machine away with gunk in the 3 way valve it could have caused the sticking.

[java man]

Good point. My detergent is in the storage locker in the same box as my scale and my other espresso paraphernalia. I won't be able to get at it again until Oct 29 . . . that is, if the developer building my apartment can meet this 4th move-in date he's given me (June 11, June 30, September 25 and now October 29). I packed all my stuff expecting to be in a hotel for only 18 June days. It's starting to get too cold to wear shorts every day.

I'll pick up some detergent before Oct 29.

[JohnB]

Also remember to swap out the screens at least once a week or just clean out the ones on your machine if your spares are in storage also.

[java man]

Everything is working fine now. I suspect the OPV was sticking. And I've learned how to dose appropriately for the S1 as a result of this. Dosing so that the tamped puck is a few mm below the "plimsol line" in the basket definitely makes for more consistent shots.

Thanks for all your help.

[oton]

Where does the top of your coffee come to, after tamping, in relation to the line in the PF?

Hi Rick. I usually dose 15-16g in the Spaz double basket, but even 17-18g tamps down below the ridge line (in the basket, not the PF). There's a pic of a 17.5g dose here. In general, I find that lower doses (not higher) are more resistant to channeling.

You've eliminated high brew pressure, stale coffee, and an inadequate grinder as potential sources of channeling. The next thing to consider is puck preparation. I'd suggest you pay careful attention to both dosing and distribution. Keep your doses moderate and (this may provoke an outburst from some of the s1cafe regulars ) consider the WDT to avoid distribution problems. A nutating tamp may help to correct minor distribution errors, but the WDT renders it superfluous. Tamp pressure and piston shape are minor issues.

I routinely use a bottomless PF on my Spaz S1, and have no problems with channeling. Despite a rotary pump and no preinfusion, I get consistently good pours with heavy or light tamps, convex or flat pistons, straight or nutating tamps. The biggest factors for me are fresh coffee, an ubergrinder, and meticulous puck prep.

Hi. I've been reading your HB Espresso Blends 2010 reviews. I find your settings very interesting. Could you explain some things, please?

_________________________
Ecco Espresso
coffee dose: 15g
brew ratio: 70-80% (shot volume 35-40ml, espresso weight 19-21g)
shot time: ~30 sec after appearance of espresso on bottom of basket
temperature range: 88C-95C (190F-203F) in increments of 1C

Protocol
Grinder: Robur with doser and (full) mini-hopper
Espresso machine: La Spaziale S1 V1, no preinfusion, brew pressure (no flow) 9.25bar, 53mm double basket, bottomless portafilter
Ground coffee into tared basket and adjusted dose to exactly 15.0g.
Very brief WDT stir with needle, then tamped to ~30#.
Pulled shots into prewarmed shot glass, stopping at ~35ml/30sec/blonding, then weighed resulting liquid.
Visually, all pours were good to excellent.
For tasting, poured shot into prewarmed cappuccino cup. Sampled straight, then with 1/2t sugar, then with increasing amounts (1-3oz) of microfoamed milk.
_________________________


Seems that your max. dosing is 16gr. Why not updose more?
35-40ml max... Do you always brew ristrettos? Why?
"~30 sec after appearance of espresso on bottom of basket" Why not start count when push the buttom?
No preinfusion... Any problem with preinfusion?