# Dead spot in centre of puck



## pandabear (Feb 12, 2014)

Upgraded my basket from Lelit standard double to IMS ridgeless 16-20g and shower screen from standard to IMS Competition. I now seem to be getting a dead spot in the centre of my shots and a very small bit of the puck sticking to the centre of the shower screen after taking the PF out of the GH.

The basket actually fits my 58.55mm tamper better, I can feel the seal there better than the standard basket. I'm using the same technique (dose into PF with funnel, WDT, distribution tool and consistent tamp), dosing the same amount (18.3g) and same grind size as I was before.

Next port of call would be to loosen off the grind slightly and possibly up dose a little if my shot ran too quick as a consequence.

Any glaring issues or fixes that I'm overlooking here?


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## Mrboots2u (May 10, 2013)

How's does the coffee taste , do you need to make these adjustments?


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## pandabear (Feb 12, 2014)

My palate isn't amazing but I would say slightly bitter, and assumed this might be because the 38g I'm getting out in 28-30 seconds is coming from the sides rather than the whole puck ie. over-extracting the sides essentially. Thinking it through maybe slightly finer grind then?


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## MediumRoastSteam (Jul 7, 2015)

@pandabear - which grinder? any mods? any accessories? single dosing? hopper fed?....


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## pandabear (Feb 12, 2014)

Mignon Silenzio. No mods. No accessories. Single dosing via standard hopper, closing gate when beans permit.

Just want to pre-empt that I don't want to get bogged down in popcorning/bouldering as a. I've ground like this since I got my Mignon and so it's been a constant fixed variable and b. there is little effect on the output (see: https://coffeeadastra.com/2019/04/12/grind-quality-and-the-popcorning-effect/)


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## MediumRoastSteam (Jul 7, 2015)

pandabear said:


> Mignon Silenzio. No mods. No accessories. Single dosing via standard hopper, closing gate when beans permit.
> 
> Just want to pre-empt that I don't want to get bogged down in popcorning/bouldering as a. I've ground like this since I got my Mignon and so it's been a constant fixed variable and b. there is little effect on the output (see: https://coffeeadastra.com/2019/04/12/grind-quality-and-the-popcorning-effect/)


 OK. If I were you, I'd try using the grinder as intended (with a hopper at least full) and see if this makes any difference (I bet it will, IMMV).

You are complaining about what ends in the cup being bitter, potentially over-extraction, with visual cues via the bottomless PF. I'm assuming this is also something you've been experiencing from the start? If not, what changed? And, if you know what changed, have you tried reverting that change?


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## Obnic (Jan 14, 2014)

pandabear said:


> Upgraded my basket from Lelit standard double to IMS ridgeless 16-20g and shower screen from standard to IMS Competition. I now seem to be getting a dead spot in the centre of my shots and a very small bit of the puck sticking to the centre of the shower screen after taking the PF out of the GH.
> 
> The basket actually fits my 58.55mm tamper better, I can feel the seal there better than the standard basket. I'm using the same technique (dose into PF with funnel, WDT, distribution tool and consistent tamp), dosing the same amount (18.3g) and same grind size as I was before.
> 
> ...


 My money says that new basket + shower screen combo has reduced the headroom above the puck, and, when it's saturated, the centre of the puck is a bit compressed. Smaller dose?


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## pandabear (Feb 12, 2014)

MediumRoastSteam said:


> OK. If I were you, I'd try using the grinder as intended (with a hopper at least full) and see if this makes any difference (I bet it will, IMMV).
> 
> You are complaining about what ends in the cup being bitter, potentially over-extraction, with visual cues via the bottomless PF. I'm assuming this is also something you've been experiencing from the start? If not, what changed? And, if you know what changed, have you tried reverting that change?


 Appreciate that, and I will try that as a very last resort as I don't drink anywhere near enough to warrant a full hopper and I'd end up with stale beans. Nor does my budget permit a Niche!

With my previous basket/screen combo I was getting a thin layer of deposited grounds on the screen and a light impression on the puck after removing the PF from the GH. This was with the same ins/outs and routine. I played around with grind size and dosing but once I'd eliminated the really harsh bitterness I was still not getting clear flavours and I assumed this was likely because I was scorching the puck with my dose not leaving enough headroom.

I changed the screen because it touts better distribution and it's integrated and I really disliked cleaning the mesh outer on the standard screen. I changed the basket because IMO the Lelit basket was too shallow for an 18g dose (hence the thin layer) and I could also visually see that the holes in the basket were not uniform, so time for a change.



Obnic said:


> My money says that new basket + shower screen combo has reduced the headroom above the puck, and, when it's saturated, the centre of the puck is a bit compressed. Smaller dose?


 When comparing how high the same 18.3g dose sits in the Lelit basket to the IMS basket, it is almost certainly sitting between 1-2mm lower. Therefore I expected more headroom and less chance of scorching.

We know that the puck swells and jumps up when hit with the water pressure, but surely it would not contribute to the residue?

This is specifically where I am getting residue now:


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## 27852 (Nov 8, 2020)

You would expect to see the shot run faster after moving to a precision basket, so that would lead you to grind finer (USP of these things is upped extraction). It could be headspace so try lowering the dose, though it seems strange on a basket that can theoretically go to 20g. You could look at the WDT, maybe put a funnel over the basket so you can stir across the entire area of the puck - I started doing this recently and have seen better results. What machine do you have - are you able to use preinfusion?

There are no holes in that area per the image - is that how it looks in real life? I think it is headspace, if the puck is flush there is very little chance the puck can saturate.


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## pandabear (Feb 12, 2014)

Kjk said:


> You would expect to see the shot run faster after moving to a precision basket, so that would lead you to grind finer (USP of these things is upped extraction). It could be headspace so try lowering the dose, though it seems strange on a basket that can theoretically go to 20g. You could look at the WDT, maybe put a funnel over the basket so you can stir across the entire area of the puck - I started doing this recently and have seen better results. What machine do you have - are you able to use preinfusion?


 Yeah, I was prepared for that. I ground fine enough to choke it with the first IMS shot so backed off and am only a little finer than I was before.

Agreed - I find it difficult to accept that 18.3g in on a 16-20g basket is not leaving enough headroom seeing as my grind is roughly there or thereabouts. I will change my WDT, that's a good suggestion.


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## 27852 (Nov 8, 2020)

pandabear said:


> Yeah, I was prepared for that. I ground fine enough to choke it with the first IMS shot so backed off and am only a little finer than I was before.
> 
> Agreed - I find it difficult to accept that 18.3g in on a 16-20g basket is not leaving enough headroom seeing as my grind is roughly there or thereabouts. I will change my WDT, that's a good suggestion.


 Looking at your picture, it is likely headspace. BH on Headspace - check the "Wet Pucks" section describing dry spots due to a lack of head space.


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## Rob1 (Apr 9, 2015)

pandabear said:


> Mignon Silenzio. No mods. No accessories. Single dosing via standard hopper, closing gate when beans permit.
> 
> Just want to pre-empt that I don't want to get bogged down in popcorning/bouldering as a. I've ground like this since I got my Mignon and so it's been a constant fixed variable and b. there is little effect on the output (see: https://coffeeadastra.com/2019/04/12/grind-quality-and-the-popcorning-effect/)


 Probably lower dose. I don't see coarsening grind and increasing dose doing anything good...

The coffeeadastra thing is crap. The app to measure grind size is crap too IIRC, you're taking a picture and measuring pixels. No account of clumping, movement, only a measure of the visible face of the grind to the camera IOW not in our three dimensions.

The effect of single dosing has been well documented empirically. Grind your dose, separate the first 6g into one cup, the second 6g into another, the third into another, repeat this 3 times until you have three doses of 18g made up of the first third, second third, final third and compare shot times. Now do the same with a grinder run with a full hopper. The difference in shot time you see through the three doses indicates the inconsistency in grind size as it drifts coarser from the start to the end of the dose when single dosing.

The stock baskets are more forgiving than IMS and VST baskets so there may well have not been an issue previously because of this in terms of how pretty a shot looks. RE: The dose size of the IMS basket. It'll depend on the density of the coffee. If it's too full it's too full, doesn't matter how much the dose weighs. I don't see 18g as particularly likely to be overfilling the basket though. With a light roast/high density it would be possible the depth is too shallow.

The spot you get grinds on the shower screen is natural. The puck will likely not be swelling and hitting the shower screen through the shot as pressure build up prevents this unless the basket is too full and there isn't enough headroom. When the shot is finished the puck can be sucked up to the screen and this spot on the shower screen is 'blank' so grinds won't be sucked through or rinsed away there....in other words the grinds sticking to the screen isn't a sign of anything. This is assuming the grinds are wet and you aren't getting a dry spot on top of the puck.


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## AJP80 (Feb 29, 2020)

pandabear said:


> Appreciate that, and I will try that as a very last resort as I don't drink anywhere near enough to warrant a full hopper and I'd end up with stale beans. Nor does my budget permit a Niche!


 Excuse the levity, but your options appear to me to be either buy a Niche or drink more coffee. Win / win!


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## pandabear (Feb 12, 2014)

Rob1 said:


> Probably lower dose. I don't see coarsening grind and increasing dose doing anything good...
> 
> The coffeeadastra thing is crap. The app to measure grind size is crap too IIRC, you're taking a picture and measuring pixels. No account of clumping, movement, only a measure of the visible face of the grind to the camera IOW not in our three dimensions.
> 
> ...


 So the single dosing effect, if I see the difference in shot time surely I find my in/out time and that's fine for me? If I filled the hopper, granted I would likely have to dial finer to account for the consistently finer grind but then once I dial in I'm at equilibrium to my previous position whilst single dosing?

This particular roast is medium/dark, it's Chocolate Point from Black Cat Coffee. I can't say for sure that it isn't touching but I'll do the coin test and reply back tomorrow morning on that front.

Good to know that the spot on the screen is normal, however does that really explain away the shot not extracting through the middle?

FWIW I have a Lelit Mara so pre-infusion, then at roughly 7 seconds I see thick drips before the everywhere bar the middle starts extracting more to form 2/3/4 streams that 'dance' around the middle and come together at around 20 seconds into the ~30 second shot.



Kjk said:


> Looking at your picture, it is likely headspace. BH on Headspace - check the "Wet Pucks" section describing dry spots due to a lack of head space.


 Will have a read, thanks!



AJP80 said:


> Excuse the levity, but your options appear to me to be either buy a Niche or drink more coffee. Win / win!


 Love it! Chunk out of my wallet or maximum caffeine high? Should start a poll 😆


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## Rob1 (Apr 9, 2015)

pandabear said:


> So the single dosing effect, if I see the difference in shot time surely I find my in/out time and that's fine for me? If I filled the hopper, granted I would likely have to dial finer to account for the consistently finer grind but then once I dial in I'm at equilibrium to my previous position whilst single dosing?
> 
> Good to know that the spot on the screen is normal, however does that really explain away the shot not extracting through the middle?


 Shot time isn't really meaningful; it can't tell you how quickly the puck erodes through a shot (increasing flow rate) or how long it takes for the first drop to appear, the only thing it can do is give you an average flow rate e.g 1ml/second = 36g in 36 Seconds. You could have a grind too fine and partially choke the machine before the puck breaks apart and produces multiple fast flowing streams and a coarser grind that extracts normally, both shots might produce the same yield in the same time but one would obviously be better than the other. That said 7 seconds is a bit early for thick drips to be appearing imo.

It's not as simple as just altering grind setting unfortunately. Yeah if the only thing that mattered was average grind size you could just set your grinder finer for single dosing and coarser for running with a full hopper, but it's the range that matters. No grinder is unimodal but an increase of boulders and fines from single dosing (or maybe just boulders) is not desirable. Assuming the dose is right for the basket, and equipment is working properly and level, uneven and poor extractions are due to poor puck prep and/or poor grind quality.

It's worth mentioning you can get extractions that look terrible on a bottomless portafilter that are absolutely fine. I regularly get extractions that look bad with lighter roasts but there's nothing wrong with the actual shot. I think a consistent dead spot in the middle could be a sign of poor distribution though. As you're using a medium-dark blend it should be fairly easy to get good looking shots with it, so I'm leaning towards poor distribution even if you are single dosing.


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## pandabear (Feb 12, 2014)

Rob1 said:


> Shot time isn't really meaningful; it can't tell you how quickly the puck erodes through a shot (increasing flow rate) or how long it takes for the first drop to appear, the only thing it can do is give you an average flow rate e.g 1ml/second = 36g in 36 Seconds. You could have a grind too fine and partially choke the machine before the puck breaks apart and produces multiple fast flowing streams and a coarser grind that extracts normally, both shots might produce the same yield in the same time but one would obviously be better than the other. That said 7 seconds is a bit early for thick drips to be appearing imo.
> 
> It's not as simple as just altering grind setting unfortunately. Yeah if the only thing that mattered was average grind size you could just set your grinder finer for single dosing and coarser for running with a full hopper, but it's the range that matters. No grinder is unimodal but an increase of boulders and fines from single dosing (or maybe just boulders) is not desirable. Assuming the dose is right for the basket, and equipment is working properly and level, uneven and poor extractions are due to poor puck prep and/or poor grind quality.
> 
> It's worth mentioning you can get extractions that look terrible on a bottomless portafilter that are absolutely fine. I regularly get extractions that look bad with lighter roasts but there's nothing wrong with the actual shot. I think a consistent dead spot in the middle could be a sign of poor distribution though. As you're using a medium-dark blend it should be fairly easy to get good looking shots with it, so I'm leaning towards poor distribution even if you are single dosing.





Kjk said:


> You would expect to see the shot run faster after moving to a precision basket, so that would lead you to grind finer (USP of these things is upped extraction). It could be headspace so try lowering the dose, though it seems strange on a basket that can theoretically go to 20g. You could look at the WDT, maybe put a funnel over the basket so you can stir across the entire area of the puck - I started doing this recently and have seen better results. What machine do you have - are you able to use preinfusion?
> 
> There are no holes in that area per the image - is that how it looks in real life? I think it is headspace, if the puck is flush there is very little chance the puck can saturate.


 Thanks to you both, I tried doing this differently this morning with an improved result (albeit off one shot).

Firstly I ground into my dosing cup, one with the tear-drop removeable bottom piece, and then released the grinds in the basket. This gave me a nice mound of coffee in the basket and ready to WDT without any hinderance or risk of spilling. I then carried on with my distributor tool and tamp method. Secondly I did the coin test with a 50p piece once tamped - only coin I had! Zero marks on the puck, not even a faint indent. Lead me to believe I was fine on headroom.

I also read more about the HX "flush and go" that I'm doing and tried to be more consistent with that this morning whereas perhaps I've not been before, leading to inconsistent puck temps. I had been flushing to roughly 98c and then pulling the shot 45 seconds after that, whereas this time I flushed to 97c and pulled within 10 seconds. GHT was showing 92c at shot end.

The shot pulled more consistently from what I saw at first but I was also keeping an eye on the GHT at the same time! However no dead spot on the shower screen and very little residual grinds on there too. Whether it's the lower temp or WDT re-do that's creating the better taste, I will have to experiment more with the temps to find that answer.

Appreciate everyone's help here, I learned a thing or two!


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## pandabear (Feb 12, 2014)

MediumRoastSteam said:


> OK. If I were you, I'd try using the grinder as intended (with a hopper at least full) and see if this makes any difference (I bet it will, IMMV).
> 
> You are complaining about what ends in the cup being bitter, potentially over-extraction, with visual cues via the bottomless PF. I'm assuming this is also something you've been experiencing from the start? If not, what changed? And, if you know what changed, have you tried reverting that change?


 Just having a think on this, wondering if this would be more viable than single dosing:

Load hopper in the morning with a decent amount of beans > grind a couple of doses over 4/5 hours > close gate and remove hopper, put remaining beans back in bag > leave the small amount of beans that are in chamber overnight then repeat next day

Would that be the best trade off with regards to bean freshness vs. grind uniformity?


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## Mrboots2u (May 10, 2013)

pandabear said:


> My palate isn't amazing but I would say slightly bitter, and assumed this might be because the 38g I'm getting out in 28-30 seconds is coming from the sides rather than the whole puck ie. over-extracting the sides essentially. Thinking it through maybe slightly finer grind then?


 Few points

1 You are not measuring extraction , your ratio mean it is highly unlikely that if measure would be over extracted., and bitter does not mean its is over extracted just that there is a taste imbalance that needs to be rectified . Bitter can happen at "under extraction "

People keep saying labelling their coffee as over extracted coz its bitter , , and making adjustments based on this assumption when a 1:2 ratio is practically never gonna measure as over extracted , if someone measured it


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