# Puck crater



## Gavin (Mar 30, 2014)

Hi,

On the enclosed photo in the top left of the puck you'll notice a dimple left in the spent puck.

This is left on every puck, in the same place, every time. I'm concerned it's affecting channelling as there appears to be water focused here. But why is this happening?

My OPV is 9 bar, I'm using the brass plate and an IMS screen. Any ideas to solve this mystery would be appreciated.


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## Gavin (Mar 30, 2014)

Second shot this morning. Same deal.


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## ThePeginator (Dec 17, 2019)

When was the last time you removed the screen and dispersion plate? Might be worth doing to see what state is in.

Do you back flush regularly with Puly Caff or similar?

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## Gavin (Mar 30, 2014)

Took it off and cleaned it about 2 weeks ago. I'll try again and do a cafiza back flush and report back.


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## ThePeginator (Dec 17, 2019)

Gavin said:


> Took it off and cleaned it about 2 weeks ago. I'll try again and do a cafiza back flush and report back.


Yeh sounds like a plan. Might be worth quickly removing the screen before / after just to check what state it's in and if you've got it properly clean after.

Beyond that I'd be removing the dispersion plate and screen for a descale and full clean of the group head.

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## El carajillo (Mar 16, 2013)

Is the shower screen bent / deformed on the edge ? or is there a coffee ground in the recess holding it off allowing water past ? Also is the machine level ?


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## ajohn (Sep 23, 2017)

If it's channelling through the "hole" I'd suspect you have too much coffee in. The position could just be down to how the grinds are positioned after loading the basket.

I'd suggest checking with a coin test. Believe a 1p can be used. Tamp, place on the puck, fit and remove and look for no impression.

John

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## Mr Binks (Mar 21, 2019)

Is it just me or do those pucks look a bit too wet as well?


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## joey24dirt (Jan 28, 2017)

This is one of my recent ones. Suspect I have too much coffee too

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## Mr Binks (Mar 21, 2019)

joey24dirt said:


> This is one of my recent ones. Suspect I have too much coffee too
> 
> Sent from my iPhone using Tapatalk


 Yeah too much coffee in the basket. How much are you dosing?


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## Gavin (Mar 30, 2014)

ThePeginator said:


> Yeh sounds like a plan. Might be worth quickly removing the screen before / after just to check what state it's in and if you've got it properly clean after.
> 
> Beyond that I'd be removing the dispersion plate and screen for a descale and full clean of the group head.
> 
> Sent from my iPhone using Tapatalk


 @Mr Binks@ajohn @El carajillo@ThePeginator

Thanks for your help guys.

So, I've taken off the screen and block. I gave them both a proper clean. Descale shouldn't be necessary. Only did it 2 months back and my water is pretty soft. The screen didn't appear to be warped or bent.

I then did my backflush with cafiza. Then burned a shot with supermarket beans to get rid of the chemicals.

I then dosed 18g into an 18g VST. Distributed, levelled with a levelling tool and tamped. I tested one pence when the portafilter was locked in, no indentation.

I pulled 38g in 30 seconds. There was a fair bit of channeling in the shot, pulling slightly to one side. The coffee tasted pretty good. Although after all that the crater was still there! I'm flummoxed.










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## Border_all (Dec 19, 2019)

New to this but is the seal in good order just thinking if a bit came out some time on the portafilter perhaps water is dripping in some way


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## joey24dirt (Jan 28, 2017)

Mr Binks said:


> Yeah too much coffee in the basket. How much are you dosing?


Only 17g. 18g VST basket too

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## Gavin (Mar 30, 2014)

Border_all said:


> New to this but is the seal in good order just thinking if a bit came out some time on the portafilter perhaps water is dripping in some way


 Seal is good. About 6 months old. No leaking.


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## El carajillo (Mar 16, 2013)

Try putting two coins under the front feet, see if it makes a difference.


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## Gavin (Mar 30, 2014)

Get this. I swapped out the brass plate and IMS screen for the factory installed kit. The difference was incredible. Much better extraction and no crater!

I'm going to test tomorrow whether it's the new screen or the block. I suspect the block.


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## AJSK66 (Jun 3, 2019)

When I was looking at getting the brass plate I saw lots of comments about worse water distribution which can cause indents in the corners similar to what you have. You can probably find such comments digging through this forum.

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## Mr Binks (Mar 21, 2019)

Gavin said:


> Get this. I swapped out the brass plate and IMS screen for the factory installed kit. The difference was incredible. Much better extraction and no crater!
> 
> I'm going to test tomorrow whether it's the new screen or the block. I suspect the block.


 Well using all of my leet knowledge and skills and taking into account your last post I'm going to go out on a limb and say that it could possibly have something to do with the after market brass plate and shower screen.

I could be wrong though....


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## Gavin (Mar 30, 2014)

AJSK66 said:


> When I was looking at getting the brass plate I saw lots of comments about worse water distribution which can cause indents in the corners similar to what you have. You can probably find such comments digging through this forum.
> 
> Sent from my SM-G955F using Tapatalk


I think it might be a problem with the holes on the brass block. They actually look bigger on the factory block.


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## ashcroc (Oct 28, 2016)

Gavin said:


> I think it might be a problem with the holes on the brass block. They actually look bigger on the factory block.


The holes on the factory block are tapered into a reverse jet. Not sure if it's by design or just to make casting easier though.


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## Gavin (Mar 30, 2014)

Used the IMS screen with the old block today. Still no crater. With all other causes eliminated the brass block has been definitively identified as the culprit for wrecking my pucks. I might try to drill the holes out a bit more to see if it makes any difference.

Interestingly, through a thoroughly non-scientific observation (my eyes), the old shower plate had a more consistent "rain shower effect" than the IMS screen!

Seems I'd "upgraded" myself into a few problems. Money well spent!


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## El carajillo (Mar 16, 2013)

Try plugging them and redrill to same position of old screen , drill smaller diameter, this will allow you to try bore similar to outlet on old screen. Possibly tapered hole was for release from mould in casting. ?


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## ashcroc (Oct 28, 2016)

El carajillo said:


> Try plugging them and redrill to same position of old screen , drill smaller diameter, this will allow you to try bore similar to outlet on old screen. Possibly tapered hole was for release from mould in casting. ?


Think you got it backwards. The brass blocks are drilled whereas the OE Ali block is cast with the tapered holes.


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## El carajillo (Mar 16, 2013)

As I read it the statement is correct. Yes I know the originals are die cast hence the tapered hole and the brass ones drilled parallel.

What I was trying to say, plug the hole's in the brass, then redrill in same position as old dispersion block. BUT drill the holes to the same size as the holes at the narrowest end

of the hole in the original plate. ie 4 mm rather than the 5 mm on top. Or even 3.5 mm to try for more restriction and allow to drill out to 4 mm if required.


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## ashcroc (Oct 28, 2016)

El carajillo said:


> As I read it the statement is correct. Yes I know the originals are die cast hence the tapered hole and the brass ones drilled parallel.
> What I was trying to say, plug the hole's in the brass, then redrill in same position as old dispersion block. BUT drill the holes to the same size as the holes at the narrowest end
> of the hole in the original plate. ie 4 mm rather than the 5 mm on top. Or even 3.5 mm to try for more restriction and allow to drill out to 4 mm if required.


Ah gotcha. Think my brass block is drilled similar to the thinner end of the taper. There was someone a year or 3 ago who reported good results drilling extra holes in the block (no tapering).


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## ThePeginator (Dec 17, 2019)

I've got exactly the same setup, brass block and IMS screen (assuming all the brass blocks are created equal and there aren't good ones and bad ones?).

Would be interesting to know how others have got on with theirs, or with modifying them.

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## Agentb (Feb 11, 2017)

I had the four dimple problem iirc, and fixed that by rotating the shower-screen a few degrees so the IMS holes don't line up with the block holes.

Some suggestions and questions - if you rotate the block 180 degrees does the problem move to the other side? (It should but ...)

Running without a PF is it obvious it is coming from one place ?

If you do identify which block hole is causing the problem i think i'd look closely and see if there is something unusual, then try cleaning it / plugging it and see what happens.

I seem to remember a previous case required two smaller drill holes being made.

Good luck ?


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## csrti946 (Mar 26, 2019)

Gavin said:


> Get this. I swapped out the brass plate and IMS screen for the factory installed kit. The difference was incredible. Much better extraction and no crater!
> 
> I'm going to test tomorrow whether it's the new screen or the block. I suspect the block.


 What is that faint ring around the outside edge of the puck? I have just started getting that on my Gaggia, which still has the factory fitted dispersion plate and screen, and it coincides with a rapidly flowing shots with spritzes.


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## Gavin (Mar 30, 2014)

csrti946 said:


> What is that faint ring around the outside edge of the puck? I have just started getting that on my Gaggia, which still has the factory fitted dispersion plate and screen, and it coincides with a rapidly flowing shots with spritzes.


 Hi

I wouldn't be too worried about the slight ring. I think it's the imprint of the edge of the dispersion block (which protrudes ever so slightly lower than the screen),made as the puck swells up during extraction and kisses the screen. That's all ok.


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## Michael87 (Sep 20, 2019)

I have this quite often. Brass dispersion plate but factory shower screen. But it falls pretty evenly when running water through it.

Hadn't thought this was an issue (lots of anti puckology sentiment online). But maybe it is?


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## DavecUK (Aug 6, 2013)

csrti946 said:


> What is that faint ring around the outside edge of the puck? I have just started getting that on my Gaggia, which still has the factory fitted dispersion plate and screen, and it coincides with a rapidly flowing shots with spritzes.


 It means life is coming full circle and you are about to real the benefit of all the hard work. Holes in the puck are often indicative of missed opportunities or upcoming potholes in life, to be avoided


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## Inspector (Feb 23, 2017)

Agentb said:


> I had the four dimple problem iirc, and fixed that by rotating the shower-screen a few degrees so the IMS holes don't line up with the block holes.
> 
> Some suggestions and questions - if you rotate the block 180 degrees does the problem move to the other side? (It should but ...)
> 
> ...


 This ∆


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## Zeak (Jun 12, 2017)

Hah! I've started getting the same issue with the new brass plate too (shower screen is OG). Even posted about it yesterday. @DavecUK thinks it's Langoriers and I tend to believe him. Potholes in life? Everything is metaphor for sure. People used to tell fortune by looking at the coffee grinds after all.

Or it's just a poor plate design which is a bummer.

https://www.coffeeforums.co.uk/topic/49777-wholes-in-the-puck/?do=embed


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## shodjoe1 (Apr 25, 2018)

I did the same,installed back the original holder and shower screen,much better extractions,no channeling,slightly faster heat up and faster cools down .Didn't like that brass thing and Ims shower screen...


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## Gavin (Mar 30, 2014)

Agentb said:


> I had the four dimple problem iirc, and fixed that by rotating the shower-screen a few degrees so the IMS holes don't line up with the block holes.
> 
> Some suggestions and questions - if you rotate the block 180 degrees does the problem move to the other side? (It should but ...)
> 
> ...


 Hey! Thanks for this.

I've been experimenting over the last week with rotating the brass block and the IMS screen to see if it changes anything. I didn't, although i'd occasionally get the odd coffee where the crater wasn't as pronounced so this is possibly, at least in part, distribution problems.

Although on a whim yesterday I took off the silicone gasket and rotated it 180. And BOOM! Crater moved to the other side! It's the gasket. Don't know why though as it looks completely uniform the whole way around!


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## ajohn (Sep 23, 2017)

if there is sufficient space for the grinds seems there other machines show that the appearance of the shower with the portafilter off doesn't mean anything at all. The water is flowing a lot more slowly when a shot is pulled and there is pressure and that makes an enormous difference to what goes on.

When I used to get it long ago it was down to a marginal situation. Machine near choked for one reason or another. Water starts getting into the grinds more in some places than others they expand and water flow though the puck gets uneven and forms a channel that might even go all the way through. Prep can make it more likely as well. Videos might show people tapping portafilter to get the grinds level before they do anything else. Anything done to the grinds has some effect. This is a poor flow  I usually do better but when making a video ...






Stop the video when flow starts to appears on the bottom of the basket. It will usually start from the edges and that is what can cause channelling. If it's even all around the edge it wont. The DB uses preinfusion so it's easier to see. The uneven flow areas are pressing onto the other areas due to pump pressure and that can cause channels to form. Later in the video some areas blond sooner than others.

So I'd be inclined to put the posters problem down to prep rather than changes to bits and pieces. The brass plate might spread the pressure on the puck in some different manner or might be a different size. Grouphead seal - can't see how that can cause it. What's more likely to cause it in this case is uneven pressure in the puck after it's tamped and flow always starts at the edges anyway. I'm not convinced that oversized tampers make any difference to this aspect but what I did before I bought one was tamp and then offset the tamper to the edge of the basket and and run it around like that giving the puck a firm polish. Reason - to get rid of some traces of grinds left behind when I knocked the puck out. I did this ages ago.

Maybe a video of prep might help. I'm wondering about light tamping and too light but could just be down to how the grinds are handled before tamping.

John

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## Zeak (Jun 12, 2017)

Just wondering if I should give my drill a go at it and enlarge the holes in the copper dispersion block.. Still getting the "craters" at the very edge of the basket. Almost always in the same spot. Tried rotating both the shower screen and the block itself with no effect. My workflow is grinding into portafilter with a funnel>WDT with a bobby pin>normal tamp. Tried whisking with and without the funnel in - slight change in location/size of the cratering but still present. Below is so far the worse case. I've examined my recent puck and the crater does not go all the down but I imagine it still causes channeling.

So yeah, anyone tried drilling? Could it theoretically work?

Technicalities:

18g in 18g basket / Cafelat gasket (fairly new) / 9 bars


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## Agentb (Feb 11, 2017)

Zeak said:


> Just wondering if I should give my drill a go at it and enlarge the holes in the copper dispersion block.


 Drilling is not reversible ... if by rotating the block by 180 degrees does not move the problem - it suggests to me - something else. 
First thought when i saw the photo was is a lip well defined from the shower block and coffee has risen higher up on the basket that i normally see.

It looks to me that when the OPV opens briefly the liquid leaves and sucks up the hole we see. There needs to be some liquid above the puck and below the shower screen.

I think i'd try a few things like

Have you tried dosing at 17g or even 16g - does it get worse or better?

The shower screen and block have to be flat and over tightening the shower screen can bend or distort it which leaves a gap that water find it easy to get through, under pressure in or out.

I would try rotating the group seal 90 degrees / rotating basket 90 / swapping the PF / tamp left handed / block a hole / swap the block / screen / check the group head before drilling holes. 👍

edit: i had a look at the other post, what 18g basket and grinder are you using?


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## El carajillo (Mar 16, 2013)

The problem appears to be a soft spot in the puck. After WDT do you level / even out the surface ? Are you applying pressure EVENLY from above ?

Is the machine completely level (brew head). Have you tried running the pump without the screen in place ? Is the flow uneven to one side ?

Changing the hole diameter in the dispersion disc will not affect the distribution.


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