# Channeling at the exact same spot?!



## Aleks_T (Jan 3, 2019)

I have the weirdest issue. I'm getting channeling at the exact same spot everytime I pull a shot. It's about 1cm to the right of the handle, regardless of basket and coffe amount.

I even tried tamping incorrectly, still get the same issue. I've recently replaced the gasket for one of those blue silicone ones and also cleaned the entire machine yesterday, same issue.

Could it be a faulty gasket? or what am I missing?


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## mr-bean (Nov 26, 2018)

Have you removed the screen block (image) and checked it's not scalled on the upper surface.









You need all 4 holes to have a clear path for the water.

If one is blocked it could cause uneven pressure across the screen.


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## Aleks_T (Jan 3, 2019)

Would be a bit odd as the screen block is brand new. Changed it to a brass one just a few weeks ago when I changed all gaskets. I'll check it of course.


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## ashcroc (Oct 28, 2016)

Have you tried rotating the shower screen to see if the channeling moves?

Laissez les bons temps rouler


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## Aleks_T (Jan 3, 2019)

I'll try that right now


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## Aleks_T (Jan 3, 2019)

Well, nothing was clogged. Tried rotating the head, no change, but as soon as I changed the gasket, everything went back to normal. No idea why that is as the gasket is brand new..perhaps it wasn't sealing properly.


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## El carajillo (Mar 16, 2013)

Possible nick or flaw in the gasket ? take a very close look.


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## 4085 (Nov 23, 2012)

is your machine on a level surface


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## ashcroc (Oct 28, 2016)

Aleks_T said:


> Well, nothing was clogged. Tried rotating the head, no change, but as soon as I changed the gasket, everything went back to normal. No idea why that is as the gasket is brand new..perhaps it wasn't sealing properly.


I've found the silicon seals can need a bit of a 'squidge' when locking the portafilter to get a good seal bit have no idea why it would cause channelling

Laissez les bons temps rouler


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## Aleks_T (Jan 3, 2019)

dfk41 said:


> is your machine on a level surface


Not 100% level no.


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## 4085 (Nov 23, 2012)

Aleks_T said:


> Not 100% level no.


Might that be the problem then?


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## Aleks_T (Jan 3, 2019)

Excuse my ignorance, I'm all new to this world but why would a slight inconsistency in level be the issue? Not questioning, trying to understand.


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## 4085 (Nov 23, 2012)

Aleks_T said:


> Excuse my ignorance, I'm all new to this world but why would a slight inconsistency in level be the issue? Not questioning, trying to understand.


because the water will always choose the path of least resistance and if the bench is not level will tilt the water to that path....I might be wrong but try to level the machine out or move it to a bench top that is level..worth a try


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## Aleks_T (Jan 3, 2019)

Even though being pressurized at 9 bar??


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## 4085 (Nov 23, 2012)

Aleks_T said:


> Even though being pressurized at 9 bar??


9 bar or not, for the coffee to escape the basket it will always seek the path of least resistance


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## Aleks_T (Jan 3, 2019)

I'll look into it. Thank you!


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## islandlad (Feb 8, 2019)

I seem to be having the exact same issue. Alas, re-seating the (also new) silicone gasket did not solve the issue. Post-extraction puck (pit always at 12 o'clock):









(Not sure what implications the crack from 3 to 9 o'clock has)

While I haven't yet got my hands on a naked PF to confirm whether the pit is indeed related to channelling (vs. say, gas escaping at the end of extraction), my suspicions are that it is a case of channelling as my shots start out as drips, and then gush. Grinding coarser simply leads to earlier gushing.

I've checked the following:

- Work top is level

- Gasket is properly seated and free of defects

- Distribution+tamping is OK (no clumps, OCD knock-off distributor, and palm tamper to ensure levelness)

- Shower screen is clean and unrestricted

- Shower plate holder is also clean and unrestricted

My dose is 14g in a 15g VST basket, 1:1 ratio, at 6 bar. Flow aside, my shots taste way over extracted. Also, my pucks never knock out in one piece, but rather, half crumbles out while the remainder remains packed into the basket's corner (likely due to tamping hard in order to get a minimum clearance between the puck and shower screen).

Really at my wits' end here. Any thoughts?

Thanks!


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## JojoS (Oct 1, 2014)

Try a 16 gram dose.


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## Aleks_T (Jan 3, 2019)

islandlad said:


> I seem to be having the exact same issue. Alas, re-seating the (also new) silicone gasket did not solve the issue. Post-extraction puck (pit always at 12 o'clock):
> 
> View attachment 38958
> 
> ...


I tried both different doses and baskets...didn't make any change. Ultimately the change back to a standard gasket did the trick for me


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## Mrboots2u (May 10, 2013)

Crack in puck post extraction means not alot. As the OPV will create some of this .

The 15 g vst is the devlis work, especially with a 14g dose in it.

You will be having to grind so fine to get 1 1:1 in that basket that it's bound to impact on micro channeling ( IMHO )

You are not over extracting at a ratio of 1 to 1, you are almost certainly under extracting, you are confusing the strength of the shot with the balance in the cup .

For you to be "over extracting " you would need a tds or of 20-22 , this is almost certainly impossible.

Your coffee may be perceived to taste "bitter" this does not mean it is over extracted.


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## ajohn (Sep 23, 2017)

islandlad said:


> My dose is 14g in a 15g VST basket, 1:1 ratio, at 6 bar. Flow aside, my shots taste way over extracted. Also, my pucks never knock out in one piece, but rather, half crumbles out while the remainder remains packed into the basket's corner (likely due to tamping hard in order to get a minimum clearance between the puck and shower screen).
> 
> Really at my wits' end here. Any thoughts?
> 
> Thanks!


I'd 2nd MrBoot's suggestions even more so. If you are getting a ratio of 1 in 30 sec the basket is going to be even more underloaded due to how fine you are grinding. That in itself may have an effect on taste all on it's own.

Not sure how your push tamper works but assume it just has adjustable depth, so in real terms you don't know what tamping pressure you are using. Personally I feel that part tamping with a chisel tool is a better option and then using a tamper in the normal way. It's easy to keep it square then.

I'm using a basket on a Sage DB that is much like using the 15g VST on other machines. On odd occasions I would get edge channelling but not enough to make that much difference to output. I cleared that up via an odd sort of polish. Bit of pressure on the tamper and offset it so that the side rests on the basket, then rotate round always keeping it in contact. Very little pressure is needed as the tamper is just ironing the edge. You may be able to do the same with your push tamper.

Increasing tamping pressure can be a method of getting cleaner used puck extraction - not a reliable one though. Correct fill levels IMHO are more likely to succeed. A very slight over fill that just about prevents full grinds expansion usually results in very clean baskets. To much overfill means grinding coarser to keep a ratio - NVG unless a "weaker" drink is neede or it just suites the bean.

John

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## islandlad (Feb 8, 2019)

After some more testing, it seems that pulling a balanced non-channelled 1:1 ristretto using 14g in a 15g VST basket is indeed impossible. I forgot to mention that it was a medium-dark roast which, due to its lower density, meant that I was getting perilously close to the shower screen. I then upped the dose to a coarser 16g (in the same 15g basket). Clearance reduced to zero (which resulted in very uneven splitting) but channelling seemed to reduce.

Next, I swapped the 15g basket for my 18g VST. I again used a 16g dose (knowing well that I should in theory keep to ±1g of 18g). Because of the deeper basket, I was now able to have some clearance. Pulled a 1:1 shot and things got better. Even split, no perceptible channelling, and OK flow (neither mouse tail, nor a gusher). Taste was still on the bitter side and lacking the sweet/chocolatey notes. Now that I've solved the channelling, I guess I simply need to fine-tune the grind/dose.

Never thought the roast - puck depth - basket type - shot would be such a complex and sensitive interdependency!


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## ajohn (Sep 23, 2017)

I use a ristretto for my wife. On the bean I usually use it adds sweetness. Not sure how you are doing them I generally find time is the best variable to use. So in my case I tune for 33g out from 13.2g grounds in 30 sec. I just reduce time to 20 sec for my wife. This approach is what I assume the ristretto and lungo terms mean - more or less water through a tuning that gives the flavours the bean should have. That may happen at any ratio from 2 up to 4 or more. If that turns out to be too weak or too strong the thing to change is the weight in.








There are other opinions though.

John

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## Aleks_T (Jan 3, 2019)

So for the sake of science, I decided to test this again. I recently ordered another silicone gasket, different vendor, different maker. Mounted it in place this morning and tried again...same results. Channeling independently of what basket I used. I have an 18g ims with exactly 18g of coffee and a 22g with 19g just for the sake of testing. Channeling

in the exact same spot on both shots but different placement of the channeling than with the initial silicone gasket...? I'm starting to wonder if the group head is uneven or something. Interestingly enough, switching back to a black standard gasket solved the issue just like last time.


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## islandlad (Feb 8, 2019)

Aleks_T said:


> So for the sake of science, I decided to test this again. I recently ordered another silicone gasket, different vendor, different maker. Mounted it in place this morning and tried again...same results. Channeling independently of what basket I used. I have an 18g ims with exactly 18g of coffee and a 22g with 19g just for the sake of testing. Channeling
> 
> in the exact same spot on both shots but different placement of the channeling than with the initial silicone gasket...? I'm starting to wonder if the group head is uneven or something. Interestingly enough, switching back to a black standard gasket solved the issue just like last time.


Are the gaskets the same height (new ones vs black one)?


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## Aleks_T (Jan 3, 2019)

Yes.


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## ajohn (Sep 23, 2017)

Aleks_T said:


> So for the sake of science, I decided to test this again. I recently ordered another silicone gasket, different vendor, different maker. Mounted it in place this morning and tried again...same results. Channeling independently of what basket I used. I have an 18g ims with exactly 18g of coffee and a 22g with 19g just for the sake of testing. Channeling
> 
> in the exact same spot on both shots but different placement of the channeling than with the initial silicone gasket...? I'm starting to wonder if the group head is uneven or something. Interestingly enough, switching back to a black standard gasket solved the issue just like last time.


I don't think i have seen any mention of what grams in to grams of shot out ratio you are using for the shot or the time. Might clear one or two things up.

Some estimate of tamping pressure could be useful too - some see the words light tamp. That is likely to mean circa 10kg. If some one has no idea it's probably best to strain a little and hope to achieve at least that.

John

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## Aleks_T (Jan 3, 2019)

ajohn said:


> I don't think i have seen any mention of what grams in to grams of shot out ratio you are using for the shot or the time. Might clear one or two things up.
> 
> Some estimate of tamping pressure could be useful too - some see the words light tamp. That is likely to mean circa 10kg. If some one has no idea it's probably best to strain a little and hope to achieve at least that.
> 
> ...


I can't see how the ratio would make a difference as to why I'm seeing channeling with one type of gasket but not the other?

I'm using a 1:2 ratio, so 18g in = 36g out. Same as I've been using with the standard gasket. Same goes for the tamp pressure. Not exactly sure on the exact amount but I'm tamping the exact same way as I always have..and the results are consistently the same. Channeling with silicone, no channeling without. I've done probably 30-40 shots with the silicone gaskets in total so it's not like it just spontaneously happened. Same spot, every time...crazy weird. (and yes, everything has been cleaned a number of times...both cafeza, burshed, taken apart etc).


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## ajohn (Sep 23, 2017)

Aleks_T said:


> I can't see how the ratio would make a difference as to why I'm seeing channeling with one type of gasket but not the other?
> 
> I'm using a 1:2 ratio, so 18g in = 36g out. Same as I've been using with the standard gasket. Same goes for the tamp pressure. Not exactly sure on the exact amount but I'm tamping the exact same way as I always have..and the results are consistently the same. Channeling with silicone, no channeling without. I've done probably 30-40 shots with the silicone gaskets in total so it's not like it just spontaneously happened. Same spot, every time...crazy weird. (and yes, everything has been cleaned a number of times...both cafeza, burshed, taken apart etc).


I asked about ratios as some one was trying 1 to 1 so thought best to check.

From various comments it seems that providing things are clean which they are it's not the machine. So something must be different when the gasket is changed. The only thing I can think of is the angle of the portafilter handle. Sometimes silicone rubber ones are rather hard when the are used initially so you may be stopping short of the angle you usually use. That in effect will reduce the fill height of the grinds as far as the machine is concerned. What may be happening with the other gasket is that the grinds are being compressed over what tamping leaves when they expand as the water goes in as they hit the shower screen.

You should know if the portafilter handle angle is different. The effect is probably machine dependant but should be kept close to 90 degrees / always the same.

If this does relate to your problem definitely over tightening with the silicone gasket fitted may help. That tends to soften them a bit as does use. And or try adding say another gram or so when the silicone gasket is fitted. Even 1/2g can make a difference on some machines.

John

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