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nicebrewmate

Uneven flow through shower screen

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Hi All,

 

First off let me say, fantastic forum you've got here, you've already helped me so much with my technique and equipment.

 

Unfortunately iv'e got a bit of an issue that i'm not sure how to address... but firstly, what i'm working with -

 

- Gaggia Classic circa 2003: reconditioned by me, new group head gasket, new shower screen and a thorough backflush / decal. Also fitted a Rancilio V2 wand

- Krups GVX2 grinder: all i could get at the time. Will buy a Eureka Mignon when Belle have them in stock again.

- 58mm stainless tamper

 

Also worth noting that I buy fresh beans from UE every week.

 

Now, onto my problem.

 

I got around to buying a bottomless portafilter and my god the channeling is strong with this one. First thought was a combination of shitty grind and shitty technique... the grind I can't do anything about but i practiced with about 250g worth of beans the other day and every single shot was still a miss.

 

Tonight I decided I was going to take the shower screen and group head out to see if they needed a clean. They were pretty much spotless but when i ran some clean water through i noticed that, with the shower screen in place, there were 2 steady streams of water and only a few holes were it was 'showering.'

 

I thought this might be an issue as when I'd googled a video earlier to make sure i put the screen on the correct way i came across this video :

which shows a nice steady shower of water coming through. I sorta figured that, if there's a heavy stream coming through the shower screen then undoubtedly it's contributing to my channeling issue.

 

Any thoughts greatly appreciated.

 

Kind Regards

 

Rob

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Yeah, I love that video... So idealistic. I have an IMS screen and have never seen my Classic do it as nicely as that unless it is the instant after a clean.

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Really, is that all it is? I'd swear the way mine is coming out it must contribute to the channeling i'm getting.

 

Order placed for a Mignon, i'm excited :)

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Yeah, I love that video... So idealistic. I have an IMS screen and have never seen my Classic do it as nicely as that unless it is the instant after a clean.

 

Agree to this. Same thing for me when I had a Classic. All wonderful immediately after a good brush of the shower screen!

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It's quite possible it may cause channeling issues. I know that I do occasionally have it occur, but not enough to concern me. It is possible that I am also just not dedicated enough with my cleaning!

Hopefully someone else can comment too as I may not be the best person for this!

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Loosen the showerscreen fixing screw by a turn or even two and see if it helps


Lots of everything: machines, grinders, roaster, beans, tampers, baskets, blah, blah

However - Too much is never enough!

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Loosen the showerscreen fixing screw by a turn or even two and see if it helps

 

My water has never come out as perfect as that, however I can be a bit heavy handed with a screwdriver... I'm off to go loosen mine right now, see if it makes any difference.

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Loosen the showerscreen fixing screw by a turn or even two and see if it helps

 

Brilliant call! that made all the difference in world, thanks :)

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I love it when a plan comes together...:-)

 

Great stuff!


Lots of everything: machines, grinders, roaster, beans, tampers, baskets, blah, blah

However - Too much is never enough!

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Well, turns out I'd probably over tightened my shower screen too, a much better dispersion now, had to make a coffee to test as well, better result in the puck too!

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No not a brass one, isn't that just to aid heat distribution though?

 

Yes.

But a few members have found there to be 2 dents on the puck when using a brass dispersion plate due to the 2 holes being smaller and nearer the edge.

 

I, like others have, will be loosening the screw of my shower screen to see if it makes a difference.

I try to never over tighten it, but will experiment to see if looser aids better distribution of water.

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Another recommendation when it comes to this is to check you aren't over filling the basket. So long as water isn't jetting out of the shower screen it should have time to build up above the puck and then push relatively evenly through it. If it is pressed against the shower screen then the distribution of water from the screen will have a much more significant impact.

 

A typical test for this is to place a 2p on the surface of a dry tamped puck, lock it into the machine and then remove it again. The 2p should have only just made an indentation on the top of the dry puck, if it has fractured the puck or been pushed in more than a hair then you have a bit too much coffee in there, try down dosing by .5-1g.

 

Your grinder is also very likely to be a cause of channeling, make sure once you have put the grounds in the PF to give them a good stir about and then levelled to provide as even a distribution of coffee as possible before the tamp.

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So long as water isn't jetting out of the shower screen it should have time to build up above the puck and then push relatively evenly through it.

 

Ive read this is the case, so not really to worry about how the water looks when it exits the shower screen as the buil

 

A typical test for this is to place a 2p on the surface of a dry tamped puck, lock it into the machine and then remove it again. The 2p should have only just made an indentation on the top of the dry puck, if it has fractured the puck or been pushed in more than a hair then you have a bit too much coffee in there, try down dosing by .5-1g.

 

 

Will our shower screen screws hanging out by a few mm have an adverse impact on this test ?

Or I guess it just means we may have to down dose a little if we were dosing the correct amount before we loosened the screw

 

Im sure now ive loosened mine as per the advice on this thread it must hang down more than it did before, maybe 1 - 2mm

 

Think I might screw it right back in again :confused:

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Another recommendation when it comes to this is to check you aren't over filling the basket. So long as water isn't jetting out of the shower screen it should have time to build up above the puck and then push relatively evenly through it. If it is pressed against the shower screen then the distribution of water from the screen will have a much more significant impact.

 

A typical test for this is to place a 2p on the surface of a dry tamped puck, lock it into the machine and then remove it again. The 2p should have only just made an indentation on the top of the dry puck, if it has fractured the puck or been pushed in more than a hair then you have a bit too much coffee in there, try down dosing by .5-1g.

 

Your grinder is also very likely to be a cause of channeling, make sure once you have put the grounds in the PF to give them a good stir about and then levelled to provide as even a distribution of coffee as possible before the tamp.

 

Thanks for the reply Dylan.

 

Yer I've checked all that already unfortunately, I really am at my wits end (didn't take long to get there, HAH!)

 

To say that the channelling I'm getting is messy is an understatement, it's literally shooting every single direction and unfortunately having a more even distribution through the shower cap didn't seem to make 1 bit of difference this morning. I'm back to praying that it's the grinder - the Mignon is arriving on Monday so we'll find out soon :)

 

I had another thought. I tend to get a decent amount of chaff in my grind. Now I figure that that's normal, UE must know what they're doing, but wouldn't the larger chunks of chaff contribute to channelling if the an uneven grind does? I have a feeling that I read/heard somewhere that a better quality grinder will breakup the chaff as well though I'm not 100% sure if I'm making that up :p

 

Cheers

 

Rob

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Ive read this is the case, so not really to worry about how the water looks when it exits the shower screen as the buil

 

 

 

Will our shower screen screws hanging out by a few mm have an adverse impact on this test ?

Or I guess it just means we may have to down dose a little if we were dosing the correct amount before we loosened the screw

 

Im sure now ive loosened mine as per the advice on this thread it must hang down more than it did before, maybe 1 - 2mm

 

Think I might screw it right back in again :confused:

 

It may well, perhaps the test is best carried out with the screw screwed in, but can be loosened after if you are dosing correctly.

 

I'm back to praying that it's the grinder - the Mignon is arriving on Monday so we'll find out soon

 

It is very very likely to be your grinder. Such grinders are really made for folks who have a machine with a pressurised basket, as this doesn't rely on an even grind to create pressure you dont notice the bad grinder causing problems.

 

I'm not sure on chaff but it would logically follow that a big flake in your puck is a invite for channeling.

 

Other things can cause channeling, even on more expensive grinders. Light roasts can be more problematic, I tried out a Hasbean roast intended for brew (very light roast, just seeing what it was like for espresso) and even with a £700 grinder I could not get a reliable shot, the EK43 folks may have had success but the point is that it varies with the bean you are using.

 

Did you mention if you are pulling your shot by weight... are you dosing 18g and getting around 34g of espresso in roughly 25 seconds? Channeling can also arise from too coarse a grind, you can try tightening it and if this produces too slow of a shot then try down dosing... but its all probably just a battle against an inadequate grinder.

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It may well, perhaps the test is best carried out with the screw screwed in, but can be loosened after if you are dosing correctly.

 

 

 

It is very very likely to be your grinder. Such grinders are really made for folks who have a machine with a pressurised basket, as this doesn't rely on an even grind to create pressure you dont notice the bad grinder causing problems.

 

I'm not sure on chaff but it would logically follow that a big flake in your puck is a invite for channeling.

 

Other things can cause channeling, even on more expensive grinders. Light roasts can be more problematic, I tried out a Hasbean roast intended for brew (very light roast, just seeing what it was like for espresso) and even with a £700 grinder I could not get a reliable shot, the EK43 folks may have had success but the point is that it varies with the bean you are using.

 

Did you mention if you are pulling your shot by weight... are you dosing 18g and getting around 34g of espresso in roughly 25 seconds? Channeling can also arise from too coarse a grind, you can try tightening it and if this produces too slow of a shot then try down dosing... but its all probably just a battle against an inadequate grinder.

 

Yer I'm dosing 18g. I've never weighed the end result tbf, going to have a crack at that tonight. I'm hovering around 27seconds for an 'espresso cup' but I've no idea how much is in that cup. when I placed the order for the grinder I also put in a little measuring espresso cup with 1 and 2 oz measurements up the side.

 

As far as the coarseness of the grind goes, (I think) because it's a stepped grinder I'm struggling to dial it in perfectly. If I go any finer than the current setting it comes through in like 45+ seconds. I've tried tamping lighter but it didn't make a whole lot of difference. Bear in mind this is fairly arbitrary as I don't actually know what volume of coffee is coming through.. could be 45seconds for 1 ounce, could be 45 for 2. hah. feel abit of a muppet that I didn't think of looking at that before. Never know, maybe i'll weight it tonight and be dead on 34g... or not.

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Repeat post please ignore

Edited by Robbo

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@Jumbo Ratty I loosened mine off last night but not so much as the screw was sticking out.

The shower screen is domed so if you really tighten it you are compressing the dome. If you loosen it just half or 3/4 of a turn the dome will expand out but the head of the screw will stay in the countersunk hole in the screen.

Hope that makes sense!?!

Edited by Robbo

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Yea being stepped makes things extra hard, you can up or down dose to compensate, so go finer but use 16-17g of coffee.

 

2oz is 57g, so if its a 2oz espresso cup you are pulling way too much in your allotted 25 seconds, but if its a 1oz you might be in the ballpark. Another indicator is that your fits couple of drops of espresso should appear after about 7 seconds.

 

If you dont already have them some 'jewellers scales' (accurate to 0.1g) are an essential bit of kit, can be picked up for 6-7 quid on ebay, or if you fancy some slightly nicer ones then look up 'brewista scales' but they are £30-40.

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Yer I use a pair of scales, think they're 0.1 to 500g. Wish I'd bought the Brewister ones now as the portafilter won't quite sit on the ones i ended up with.

 

Speaking of portafilters, I have a triple basket as well, any thoughts on how much grind i should put in that one?

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21g i think.

 

If you have scales then absolutely start weighing your output!

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Got my grinder today... omg what a difference. took me 5 tries to dial it in and on the 5th is was nigh perfect - no channeling at all and beautiful tiger-striping all the way down :D Stoked! thanks for the help guys.

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Haha, it was always the most likely culprit. Enjoy the coffee.

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