Help to diagnose channeling before i get discouraged

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lamarzoccofan92

#1: Post by lamarzoccofan92 »

Recently got really into espresso and got myself a linea mini and niche zero grinder which was a significant upgrade from the breville barista pro I have been using for a long while. Based on the reputation of these machines, I thought transitioning will be a breeze. How wrong was I! I got myself a bottomless portafilter last weekend and have since been troubled by channeling issues EVERY single shot i pulled. I have no idea why and have watched so many videos to improve on my technique but I still have no idea what is wrong with my technique. To be honest, I am feeling a little dejected and discouraged but I really hope someone can point out where my faults are and how can i improve on it. I have been running through SOOO much coffee to the point i bought supermarket beans just to practice, but to no avail.

Please help.

These are my hardware:
La Marzocco Linea Mini, Niche Zero Grinder, Pesado Bottomless Portafilter, IMS 18g Ridged Precision Basket, Pullman 19-22g Precision Basket, Pullman Wedged Distribution Tool, Pullman BigStep Tamper

I will try to walk you through step-by-step in as much detail as possible. Again, Thanks for your patience.

I am using the pullman 19-22g basket, dosing 20g ground coffee for this example. Have also done the same with 18g IMS basket, 18g coffee, results pretty much the same. Therefore I'm sure it's something to do with my technique.

I have tried transferring the grounds from the niche to the portafilter in 2 different ways. Initially I inverted the dosing cup into the portafilter, give it a few shakes and remove the dosing cup. However, due to the long walls of the dosing cup, I realized that there is a huge and deep gap between the grounds and the walls of the filter basket and it is quite hard to get rid of.

I changed my technique to slowly tipping the dosing cup and pouring the grounds into the basket instead. I get a bit of spillage here and there, nothing too much and i usually grind extra to compensate for the expected spillage. I always weigh my portafilter with grounds in before distributing to make sure there is 20g of coffee in there. I am planning to get/DIY a funnel to make this more seamless.

This is how it looks after transferring the grounds:


I give it a few taps by the side of the portafilter to level the grounds:


Then one or two firm taps on the bench to settle it:


Use the pullman distribution tool: (Note: I feel like this might be the point of error, I have yet to calibrate the tool depth perfectly. But then again, I tried tamping the grounds without using the tool, making sure the prepared puck is as level as possible, the results are largely similar)


Tamping:




Then i purge the grouphead: (Not sure if there is anything amiss regarding the flow of water from the grouphead, Uploading this just for completeness and see if maybe someone could spot something off, Gauge reads slightly above 9bars WITHOUT any a puck)
With an empty portafilter attached:
Here comes the shot Channeling :( I have set the linea mini on a 1 second prewet and 3 second delay, also tried with no pre-infusion but largely the same as well, if not more channeling. ALSO note that, when I am pulling a shot with a puck, the gauge now shows 10 bars of pressure. I am not too sure why, but La Marzocco told me that is nothing to worry about so i took their word for it.
The puck after this shot:
So many holes, sometimes even more



Underside of the grouphead post extraction


I backflush the grouphead almost everyday. I have removed the shower screen and gave it a soak and brush down so everything is clean.

Still no idea why :(

If anyone can take some time off and help me out that would be great! Again, thank you so much for your time.

Also another thing is my steam wand seems to be spurting our water after closing the valve, have never played with another linea mini before so i'm not sure if this is normal

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shawndo
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#2: Post by shawndo »

Looks like you just need to grind finer to me. You mentioned the 18-20g dose but not how much out and time (flow rate).
Also, I've found that the temperature being wildly off does affect my flow, so not sure if you calibrated the temp on the linea or not.
Darmok and Jalad at Tanagra

lamarzoccofan92

#3: Post by lamarzoccofan92 » replying to shawndo »

Flow rates are pretty inconsistent, depending on the amount of channeling i would say, but I would say on a relatively good shot, it takes around 35 seconds to pull 40g of liquid espresso, including the pre-wet time and delay.

I have no idea how to calibrate the temperature as I do not have any equipment to accurately measure the temperature. I have been told that all machines are tested before getting sent out to customers and the linea mini is supposed to be very temperature stable. I have set the temperature at 94.5 Celsius using the Home App, so i assume it is the case. I would definitely try grinding a little finer and see if it gets better.

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shawndo
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#4: Post by shawndo »

A video of the whole prep procedure might help also
*edit*
The pic of your puck sparked a memory of when I forgot to tamp once. Obviously you are tamping, but just thought I'd drop this here
https://www.baristahustle.com/blog/how- ... -you-tamp/
Darmok and Jalad at Tanagra

pcrussell50

#5: Post by pcrussell50 »

Also "fast" high EY baskets are notoriously finicky. Try a high quality "normal" basket like an EPNW HQ. And see if that improves things for you.

Then if you still want to pursue the n'th degree of EY (and not all coffees taste better from that pursuit), we can go from there.

-Peter
LMWDP #553

lamarzoccofan92

#6: Post by lamarzoccofan92 »

shawndo wrote:A video of the whole prep procedure might help also
*edit*
The pic of your puck sparked a memory of when I forgot to tamp once. Obviously you are tamping, but just thought I'd drop this here
https://www.baristahustle.com/blog/how- ... -you-tamp/
I'll try to record one when i have the free time. I feel like i have been tamping with sufficient force, i basically push down with all my might until there is no room for compression. Assuming if there is nothing wrong with the machine, which i doubt there is, I am thinking there is something wrong with my distribution method that results in unequal density of the puck. Problem is i can't tell myself.

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shawndo
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#7: Post by shawndo »

The other factor is the grinder. Have you used that one successfully before on your previous/different machine? I don't really know anything about the niche quality control .
Darmok and Jalad at Tanagra

lamarzoccofan92

#8: Post by lamarzoccofan92 »

pcrussell50 wrote:Also "fast" high EY baskets are notoriously finicky. Try a high quality "normal" basket like an EPNW HQ. And see if that improves things for you.

Then if you still want to pursue the n'th degree of EY (and not all coffees taste better from that pursuit), we can go from there.

-Peter
The problem is I am pretty much a perfectionist and very stubborn. I don't like to just sweep things under the rug. I understand that there is a smaller margin of error with precision baskets but in a way I am grateful for that because that amplifies the mistakes I make which i might have not known earlier. Before diving deeper into experimenting with flows, preinfusion and temperatures, I just want to correct my technique and this amount of channeling is a clear sign of me lacking in that department. That is also the main reason why i bought the bottomless portafilter.

lamarzoccofan92

#9: Post by lamarzoccofan92 »

shawndo wrote:The other factor is the grinder. Have you used that one successfully before on your previous/different machine? I don't really know anything about the niche quality control .
Good point. My previous machine was a Breville/Sage barista Pro. It has an inbuilt grinder so I didn't needed a separate grinder for that machine. I would say it works pretty well, but then again I really struggled to pull cafe quality shots with that machine and have no idea how well my techniques are since it only comes with a spouted portafilter. I have since sold the machine after getting the Linea Mini/Niche combo. I have never pulled shots with the niche on any other machines. The grinder is also brand new, ground less than 1kg of coffee so i'm not sure it is because the grinder needs seasoning.

That being said, I think I could possibly bring some beans to a local coffee shot and get them to grind my beans for me and try pulling a few shots with the niche. I'm not sure if that is a good idea but if that works out, it might just narrow down the problem.

jevenator

#10: Post by jevenator »

I'm a firm believer in a good random, aggressive, but controlled and neat WDT on the whole basket.

Your shots should come in evenly like this


And come to a steady stream like this


Seems like your shot is going way too fast as well so you have to grind finer. You can have success with your baskets. Don't use supermarket coffee as if they are not fresh (1-3 weeks) then it won't build pressure.
LMWDP #643