# Clumping - why do you care?



## bongo (Apr 20, 2014)

*Do you think clumping makes any difference once tamped?*​
Yes, it's like day and night1337.14%No, not in my cup2262.86%


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## bongo (Apr 20, 2014)

As per the title. There's often a level of discussion on here regarding how to reduce clumping.

What difference does it make? (facts and figures rather than opinions please)...

My quick theory is that is makes no difference. my reasoning being that as soon as you tamp the coffee all clumps are obliterated. Leaving them untraceable. Only resembling the remnants of what they once were - kind of like the temples destroyed by IS recently.

Yet, there's always discussion on how to stop clumping. I say "easy - use a tamper" (like normal).

Let the theorists, the statisticians, scientists, craftsman and 'nobbers' commence the final debate ever on this HUGE issue.

Go.

For those who don't want to speak publicly - do make your vote whether you think it matters a jot, or not...


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## jeebsy (May 5, 2013)

bongo said:


> only resembling the remnants of what they once were - kind of like the temples destroyed by is recently.


LOLs


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## Fevmeister (Oct 21, 2013)

looooool


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## aaronb (Nov 16, 2012)

If you already have a clump and then tamp then the area where the lump is will be more dense than the other areas.

A naked portafilter will easily show up poor distribution because of clumps, no facts or figures needed.


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## The Systemic Kid (Nov 23, 2012)

https://londiniumespresso.com/blog/clumping-coffee-grinds-dont-cause-channelling-and-dont-mean-your-grinder-is-poor


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## bongo (Apr 20, 2014)

aaronb, do you think when an even pressure (from the base of the tamper), far greater than the pressure binding the particles in the first instance, is applied to a mobile substrate (coffee grounds) that the 'density' doesn't become far more / entirely uniform?


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## bongo (Apr 20, 2014)

The Systemic Kid said:


> https://londiniumespresso.com/blog/clumping-coffee-grinds-dont-cause-channelling-and-dont-mean-your-grinder-is-poor


nice short piece... good find


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## hotmetal (Oct 31, 2013)

I've always thought this but never dared to say anything as the accepted group think seems to be that clumps are the Devil's tag nuts and should be avoided like the plague, Starbucks espresso and flavoured syrups multiplied by each other. I think this is the first thread that has said that clumps make little practical difference, which seemed intuitive to me due to the relatively weak forces holding a clump together cf tamping and the subsequent preinfusion. I just assumed that as clumping was apparently a big deal and few on here had disputed it, that they must know something I didn't. Sounds to me a bit like hifi forums discussing the importance of which direction your cables run (don't go there! )


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## The Systemic Kid (Nov 23, 2012)

Lot of myths in coffee making


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## MWJB (Feb 28, 2012)

bongo said:


> aaronb, do you think when an even pressure (from the base of the tamper), far greater than the pressure binding the particles in the first instance, is applied to a mobile substrate (coffee grounds) that the 'density' doesn't become far more / entirely uniform?


Using the logic that simply a tamped puck will give an even density, nobody should be struggling with low/uneven extractions. This just isn't so.

Ideally, the water needs pass evenly through the puck, treating as many grinds as possible, as similarly as possible, anything that prevents this is potentially a problem. Why are the grinds clumping in the first place? Something is attracting them together, then you are compressing them together further rather than breaking that attraction? This is then reducing the coffee mass that is exposed to the water, water that just has a few tens of seconds to do its job.


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## hotmetal (Oct 31, 2013)

The Systemic Kid said:


> Lot of mythOs in coffee making


Fixed it for you!  

A myth is a female moth. Dithcuth.


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## risky (May 11, 2015)

The Systemic Kid said:


> https://londiniumespresso.com/blog/clumping-coffee-grinds-dont-cause-channelling-and-dont-mean-your-grinder-is-poor


Seems pretty conclusive to me! Great link.


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## aaronb (Nov 16, 2012)

bongo said:


> aaronb, do you think when an even pressure (from the base of the tamper), far greater than the pressure binding the particles in the first instance, is applied to a mobile substrate (coffee grounds) that the 'density' doesn't become far more / entirely uniform?


Yep I do, and backed up by my own (not scientific) tests too using a naked PF and observing channeling. That said I dont get clumps very often on the Vario so its a non issue for me.


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## aaronb (Nov 16, 2012)

risky said:


> Seems pretty conclusive to me! Great link.


Id look to more than one source and do your own research.

The article was from ages ago (things change fast in the coffee world) and has no facts and figures to back it up either.


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## bongo (Apr 20, 2014)

MWJB said:


> Using the logic that simply a tamped puck will give an even density, nobody should be struggling with low/uneven extractions. This just isn't so.


What you're saying is true. But it's also mis-direction. the channelling you're talking about may be solely to do with differences in the holes of the basket altering flow, areas around the edge untamped due to poor tamper fit, and an uneven tamp, so different depths of coffee.

The density, i.e., loosely defined here as coffee parts per volume will be relatively equal under the tamper once pressed.



MWJB said:


> Ideally, the water needs pass evenly through the puck, treating as many grinds as possible, as similarly as possible, anything that prevents this is potentially a problem.


sounds good so far.



MWJB said:


> Why are the grinds clumping in the first place?


I actually dunno. Static? Cohesion from moisture / oils?



MWJB said:


> Something is attracting them together, then you are compressing them together further rather than breaking that attraction?


I scientifically disagree. Put a lump of wet sand in a bucket. It sticks together like a clump. Now stand on it. It breaks apart. Oh my god. you just destroyed a clump!

The clump changes shape. It does not become a smaller volume of highly dense 'clump' (i.e., denser by your suggestion - which is probably wrong I'm afraid).

But to continue the thought process, No I do not know what makes a clump form. My first guess would be static, in which case it will dissipate once played with (tamped). If this is otherwise moisture or oil, then there's no way to remove the 'clump' other than grinding fresh coffee with no clumps.

I hope that makes sense....?


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## bongo (Apr 20, 2014)

aaronb said:


> Id look to more than one source and do your own research.
> 
> The article was from ages ago (things change fast in the coffee world) and has no facts and figures to back it up either.


Clumps don't change. They don't listen to rumour. They defy all grinders in front of them (apart from mine of course).

Please do point out other 'research' we can call upon. Maybe some to support your suggestions?


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## aaronb (Nov 16, 2012)

bongo said:


> Clumps don't change. They don't listen to rumour. They defy all grinders in front of them (apart from mine of course).
> 
> Please do point out other 'research' we can call upon. Maybe some to support your suggestions?


You haven't posted any research that supports yours either. All we have is an opinion piece, which is as valid as mine is.


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## aaronb (Nov 16, 2012)

bongo said:


> the channelling you're talking about is to do with differences in the holes of the basket altering flow, areas around the edge untamped due to poor tamper fit, and an uneven tamp, so different depths of coffee.


Most people on this forum are clever enough to have ruled that out. Pretty much everyone is using IMS or VST baskets with highly accurate hole distribution and size, and using decent tampers that fit snugly or nutation. An uneven tamp is also very easy to see in the basket, especially a ridged one. If you rule these factors out and continue to get channelling then clumps is an obvious one to investigate.


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## risky (May 11, 2015)

aaronb said:


> Most people on this forum are clever enough to have ruled that out. Pretty much everyone is using IMS or VST baskets with highly accurate hole distribution and size, and using decent tampers that fit snugly or nutation. An uneven tamp is also very easy to see in the basket, especially a ridged one. If you rule these factors out and continue to get channelling then clumps is an obvious one to investigate.


I'd look to uneven flow from the shower head before clumping. Especially on lower end machines.

My grinder doesn't clump, at least not to the naked eye, yet I still get channeling from time to time. The way I solved most of my problems was to under dose. 17g in an 18g VST solved a lot of my woes. This would point to something to do with expansion space for the puck?


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## bongo (Apr 20, 2014)

aaronb said:


> An uneven tamp is also very easy to see in the basket, especially a ridged one. If you rule these factors out and continue to get channelling then clumps is an obvious one to investigate.


true... but that still does't support your density suggestion. It only supports why you may be interested in looking at clumping... i.e., other avenues covered.


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## MWJB (Feb 28, 2012)

bongo said:


> What you're saying is true. But it's also mis-direction. the channelling you're talking about is to do with differences in the holes of the basket altering flow, areas around the edge untamped due to poor tamper fit, and an uneven tamp, so different depths of coffee.


No "mis-direction" intended. I thought we were talking about the relative clumpiness of grinds, exclusive of different baskets etc.



bongo said:


> The density, i.e., loosely defined here as coffee parts per volume will be relatively equal under the tamper once pressed.


That's a huge assumption. Even so, if you don't know what is binding the particles, you can't know how much available surface area is shown to the water.



bongo said:


> I actually dunno. Static? Cohesion from moisture / oils?


Same coffee different grinders, rules out moisture etc, assuming as many factors being equal as can be.



bongo said:


> I scientifically disagree.


OK, you have some/any data?



bongo said:


> Put a lump of wet sand in a bucket. It sticks together like a clump. Now stand on it. It breaks apart. Oh my god. you just destroyed a clump!
> 
> The clump changes shape. It does not become a smaller volume of highly dense 'clump' (i.e., denser by your suggestion - which is wrong I'm afraid).


We don't brew sand or remark on relative clumpiness of sand from one grinder to another. Coffee is porous, honeycomb like structure, we don't simply want to get the impenetrable surface wet, we need the water to permeate the particles somewhat to wash out solubles. You again have some evidence that I'm "wrong"?

You've aligned yourself with "science" & made definitive statements about what is "wrong" but without presenting any logic, or data. I'm all for mythbusting, but replacing a perceived myth with another myth that you like the sound of isn't mythbusting, it's partisan propaganda. You're sure you have the answer to your question, even before you presented it, it seems pointless to discuss it further.


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## forzajuve (Feb 2, 2011)

The cause of channelling is uneven distribution. Clumping is an enabler of uneven distribution. Clumping is an issue if you cannot effectively redistribute the coffee evenly across the basket.


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## Dylan (Dec 5, 2011)

forzajuve said:


> Clumping is an issue if you cannot effectively redistribute the coffee evenly across the basket.


This.

Clumping is a precursor to uneven distribution, an even bed of coffee makes a difference to channeling in my completely unscientific opinion, but as there has been nothing else here, I guess it counts.


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## Kyle548 (Jan 24, 2013)

Null-hypothesis; coffee clumping has no effect on relative distribution across a basket and extractions are always the same relative to other factors.

Hypothesis; coffee clumping has an effect on extraction observable in isolation of other factors.

Really though, if you are to test this - you can't compare two different grinders - you would have to compare the same clumpy grinder a number of times with various levels of declumping.

Then run the experiment again to make sure results are repeatable.

The control can be a fluffy grinder, but can't factor into the results as then grind size, particle shape, ect, ect are contributing factors and it becomes is grinder A better than B.


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## bongo (Apr 20, 2014)

MWJB, i'm going to try and respond but It's a bit OTT to try and quote, quotes within a quote so i hope you can follow my response, else it won't make any sense.



MWJB said:


> That's a huge assumption..


No it's not. Using your own statement of "assuming as many factors being equal as can be", if you apply a pressure to a substrate withing a given space, the density will be roughly equal throughout the substrate. This would be best demonstrated using water. Given that this isn't water and there will be an amount of friction the density wont be without difference, but it'd be as close as is worth arguing about.



MWJB said:


> Even so, if you don't know what is binding the particles, you can't know how much available surface area is shown to the water.


True, we don't seem to know, at least no one who's commented so far. But I don't follow the surface area part. We were talking about density, which I thought i'd explained quite well with my sand in a bucket analogy.



MWJB said:


> Same coffee different grinders, rules out moisture etc, assuming as many factors being equal as can be.


This may be the place where you can NOT assume factors being equal. It's not the same coffee. If you grind a dose from a roast once, it's gone. The next lot, from the same roast is different.

Open question - do we (anyone) know what the variance is between beans for oil content, moisture etc - maybe thats the difference that leads to clumping? (question not a statement).



MWJB said:


> We don't brew sand or remark on relative clumpiness of sand from one grinder to another. Coffee is porous, honeycomb like structure, we don't simply want to get the impenetrable surface wet, we need the water to permeate the particles somewhat to wash out solubles. You again have some evidence that I'm "wrong"?


Firstly I don't think I said you were wrong. What I said was tamping a clump within a dose in a portafilter wont make the 'clump' any denser than the rest of the dose.



MWJB said:


> You've aligned yourself with "science" & made definitive statements about what is "wrong" but without presenting any logic, or data.


I did present logic (i.e., sand bucket analogy) Whether it was right or wrong, it was presented. Please read the post. I don't have data, nor it seems does anyone else . I, probably like most, just don't have the resources.

I opened the question and debate as from experience, there are some pretty 'techy' people here who have and might be able to put meat on these bones and shut up this argument - much as Matt Perger did regarding tamper fit.

The only science i can give you is so far is that twice as many people have said that it doesn't make a difference as those that think it does. But i still don't know if that's right...


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## Dylan (Dec 5, 2011)

bongo said:


> No it's not. Using your own statement of "assuming as many factors being equal as can be", if you apply a pressure to a substrate withing a given space, the density will be roughly equal throughout the substrate. This would be best demonstrated using water. Given that this isn't water and there will be an amount of friction the density wont be without difference, but it'd be as close as is worth arguing about..


Hoe could you possibly know that?

You assert it like its fact, which it isn't, yet in the OP ask for facts and figures only....


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## garydyke1 (Mar 9, 2011)

The Systemic Kid said:


> Lot of myths in coffee making


Lots of mythos in the coffee making, too


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## Dylan (Dec 5, 2011)

bongo said:


> The only science i can give you is so far is that twice as many people have said that it doesn't make a difference as those that think it does. But i still don't know if that's right...


That isn't science.


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## garydyke1 (Mar 9, 2011)

bongo said:


> if you apply a pressure to a substrate withing a given space, the density will be roughly equal throughout the substrate.


Is 'roughly equal' enough for angry 130psi water and the substrate being the only resistance ?


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## jlarkin (Apr 26, 2015)

I think clumping makes a difference.

Nothing to back it up apart from personal experience but in the absence of any facts and figures it's good enough for me.


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## "coffee 4/1" (Sep 1, 2014)

for me on lever, if i use battery whisk on the ground coffee not using high-end grinder a much better extraction, as opposed to not whisking, no idea of the physics of this method but works for me.


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## Kyle548 (Jan 24, 2013)

\ said:


> for me on lever, if i use battery whisk on the ground coffee not using high-end grinder a much better extraction, as opposed to not whisking, no idea of the physics of this method but works for me.


That might be due to even distribution rather than clumping.

If it's a cheap grinder its entirety possible that the grinds are not consistent.

Mixing them probably makes sure distribution of fines and the like is more even rather than stopping clumping.


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## urbanbumpkin (Jan 30, 2013)

From someone who used to own a Mignon, I found that clumps do exist and don't vanish with just tamping


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## bongo (Apr 20, 2014)

Dylan said:


> That isn't science.


Why not?


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## Dylan (Dec 5, 2011)

Because you are just plucking numbers from one thread based on completely subjective opinions.

It's like me googling clumping, reading a thread on a random forum which has 10 people declare they cured channeling by eliminating clumping and saying "there, see, science!"


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## bongo (Apr 20, 2014)

@Dylan in the world of science, opinions count for a lot.

I disagree that subjective opinions do not form 'science'. While I have not run a Pearson's Chi-squared test on the 'data', but pointed to the descriptive statistic (at the time 4 no vs 2 yes, or simply put, twice as many people, or 100% more people how ever you wish to phrase it). At the current count twice as many people have agreed that clumping does not make a jot of difference once tamped, so for this brief period, the only fact (science or not)I have stated, still stands true..

In qualitative science, opinions are what forms most arguments. Opinions categorised in to yes no variables also form much quantitive science, like this, aswell.

They all wrong too?


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## Dylan (Dec 5, 2011)

In conducting a survey of any merit whatsoever you have to look at all variables and the influences on peoples responses and judge how this influences the responses you get.

I cant believe I'm having a discussion on whether totting up positive and negative responses to a forum thread constitutes 'science'. People do dodgy, ridiculous, 'unscientific' research all the time and call it science, you can, very loosely apply a definition of science to your polling of the thread if you like, but I will reserve the right to think that is preposterous and state that it is not, infact, science.


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## MWJB (Feb 28, 2012)

Bongo, you have tiny sample opinion poll on what people think. You do not have anything like answer on whether clumping affects extraction.

What is channelling? Does tamping negate channelling? If tamping force (unspecified) is enough to break any attraction between grounds & ensure that the puck is of even density, even mutual attraction between grounds & allows full & even extraction, then the pressure of extraction at 60-170PSI should guarantee it, gold plated, bullet proofed & copper bottomed...but it doesn't.


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## bongo (Apr 20, 2014)

MWJB said:


> ... You do not have anything like answer on whether clumping affects extraction.


I totally agree. In fact, if you read back what I have said, you will soon see that I have not, at any point, said that the poll which I have referred too does or does not prove this clumping theme.

I *have* disagreed that opinions do not count toward/as science when collected.

What I have said is:



bongo said:


> so far ..... that twice as many people have said that it doesn't make a difference as those that think it does. But i still don't know if that's right...


. Which I think is the only fact that has been presented by anyone so far.

So please do get off of your high horses, and read what I've written. Read it carefully. Then by all means continue a logical debate.

As per the start of this whole theme/discussion, I wondered if anyone had any light, on whether or not clumping makes a difference? Yes, the theme has been covered before. But things change. Technology advances. New idea's and research is done all the time, so I re-opened the question. I thought it would be interesting as so many talk about it, but no one has any clear evidence that it makes any difference.

I asked if anyone knows why clumps form? so far, no one does.

I asked that rather than stating assumptions or opinions, if anyone could offer an evidence either way. No one has.

While I think we may be able to agree that it is possibly very hard to do, I hoped someone may have the skill, time, equipment etc to do this. There are some gifted people here.

Hell, if I suggested to some that people weigh their coffee input, measure the extraction in the output, digitally control the temperature etc etc they would think I was mad. But, these things have been measured and supported with more evidence than what has been presented here.

So thank you for your two pence, but I hope I've made my stance clear. I don't know if clumps matter. Do you? If so, show me how.....I'm interested to know.


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## seeq (Jul 9, 2011)

As scientific as I can manage is this....

6 shots in a row (10 minute break between), 18g in. No change in grind setting or tamp pressure (as much as I can manage) and the output as followed for a 27s pour.

Shot 1 (clumps broken up) 28.2g

Shot 2 (clumps not broken)

28.8g

Shot 3 (clumps broken) 26.7g

Shot 4 (clumps not broken)

32.2g

Shot 5 (clumps broken)

28.0g

Shot 6 (clumps not broken)

29.2g

Does that tell us anything..... Not really, still far too many variables, but was fun trying them all!

P.S. My opinion on whether polls count as science - regardless of the amount of people polled it's not science..... Else the conservatives would scientifically be the best political party in the country!


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## MWJB (Feb 28, 2012)

You are asking a lot of questions & making statements that differ from your original question & thread title, it makes it hard to discuss the pertinent matter because you keep flitting around.

I think your higher giraffe just squished my not so high horse.

You said you have no facilities to test any of this out. Do you have a clumpy grinder, an espresso machine, scales & a timer? Brew 10 shots, clumpy straight into the basket, just tamp & pull the shot, evaluate (anything that can be measured & quantified will also show up in the taste, it would be good to describe some objective parameters but subjective assessment will get you started), then compare to 10 shots made with de-clumped clumpy grounds. Compare shot times for the ratio, alternate between clumpy & de-clumped...you could do this over a while, best to keep to the same coffee & grind setting for each pair at least. Then look back at your notes (brew ratio, shot time, preference score of taste, any stand out attributes).

Checking the EY of shots would be good, only problem might be if all your shots are under extracted then a difference might not be clear.

Static is the most likely cause of clumping (but may have more than one cause itself) but it's probably not that relevant (unless you're trying to design a clump free grinder with no external anti-clump measures) because clumps happen...then we decide whether we need/want to deal with them. If clumping is more pronounced at finer grinds, but coarser grinds prevent us from hitting desired extraction, then we have to accept clumping at finer grinds & find a solution (if we so choose).

Evenness of extraction, clumping, distribution all dovetail...any single defect that prevents a good extraction, either by itself, or in conjunction with another, becomes the lowest common denominator.


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## bongo (Apr 20, 2014)

@seeq - thanks for the time and effort. Other than differing volumes in output, much difference in taste?



seeq said:


> .... Else the conservatives would scientifically be the best political party in the country!


Now that's a whole new direction to discuss..sssssome other time though


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## bongo (Apr 20, 2014)

MWJB said:


> You said you have no facilities to test any of this out. Do you have a clumpy grinder, an espresso machine, scales & a timer?


No clumpy grinder, and scales currently broken, but I get the idea. I'd also suggest the comparison to no clumps (though not sure how you'd get this from the clumpy grinder) in order to make a fuller comparison, i.e., clumpy + tamped, broken clumps and tamped, no clumps and tamped.



MWJB said:


> Checking the EY of shots would be good,...


By EY you mean extraction yield? If so, definitely can't do this.

Taste is all I'd be able to go on.

In case anyone asks why the interest if I don't have a clumpy grinder - I thought It might help myself and others understand the significance of it if there is any, or otherwise just ignore all the clumpy talk...

P.s. just had to shot the giraffe...

....steak anyone?


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## MWJB (Feb 28, 2012)

FF to 14:20 & 21:06...

http://www.tampertantrum.com/tamper-tantrum-lite-the-fumbally-colin-harmon/


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## Drewster (Dec 1, 2013)

bongo said:


> .......... there are some pretty '*techy*'......


Was that a typo? Did you mean *tetchy*?


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## seeq (Jul 9, 2011)

bongo said:


> @seeq - thanks for the time and effort. Other than differing volumes in output, much difference in taste?


Not really. Either clumps make little/no difference, or more likely my experiment was not very scientific.


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## MWJB (Feb 28, 2012)

bongo said:


> No clumpy grinder, and scales currently broken, but I get the idea. I'd also suggest the comparison to no clumps (though not sure how you'd get this from the clumpy grinder) in order to make a fuller comparison, i.e., clumpy + tamped, broken clumps and tamped, no clumps and tamped.
> 
> By EY you mean extraction yield? If so, definitely can't do this.
> 
> Taste is all I'd be able to go on.


You'd need to check EY's to compare clumpy, de-clumped & non-clumpy as you'd need a different grinder to produce the non-clumpy grinds, so you'd have to establish a datum...even then it adds a variable (different grind distribution?).

If your extraction yields are significantly higher/lower/less even you'll taste it, measuring EY will tell you where you are (& give you ideas as to what to do about it) are but doesn't affect the taste of the coffee because it is already made.


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## bongo (Apr 20, 2014)

I can't watch it all now but I will. Seems to be a really interesting video. Thanks for the post.


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## shrink (Nov 12, 2012)

MY SJ clumps a fair bit, even with doser modifications. If I don't stir those clumps out (which I hate doing) then my naked PF sprays everywhere, the extractions are horrid, and the taste is poorly developed with bitter undertones.

If I stir the clumps out and then tamp, I get a lovely central pour from the middle of the PF, and the taste becomes rich and sweet.

I think that pretty much ends the argument for me. Clumps are a shot killer.


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## Dylan (Dec 5, 2011)

shrink said:


> MY SJ clumps a fair bit, even with doser modifications. If I don't stir those clumps out (which I hate doing) then my naked PF sprays everywhere, the extractions are horrid, and the taste is poorly developed with bitter undertones.
> 
> If I stir the clumps out and then tamp, I get a lovely central pour from the middle of the PF, and the taste becomes rich and sweet.
> 
> I think that pretty much ends the argument for me. Clumps are a shot killer.


Thats all the scientific proof I need.


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## Kyle548 (Jan 24, 2013)

Dylan said:


> Thats all the scientific proof I need.


Anecdotal evidence is not scientific evidence; particularly when you don't know what else is going on.


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## shrink (Nov 12, 2012)

Scientific evidence is hypothesis, test, get result, repeat, get another result, repeat, get another result, until you have a statistic that is consistent enough to be considered fact. Don't confuse science for anything other than a series of proven theories.

I've tested many many ways of making coffee at home, as I absolutely hate fuss. I'd love to not stir anything. However, given identical dose, of identical coffee, brewed at identical pressure, with an identical machine. A non stirred clumpy dose, results in spraying and multiple streams from the naked PF, as well as early blonding.

Stiring the clumps results in a more even pour which results in a better taste in my cup.

Of course you only have my "anecdotal" evidence to go on in this case. But for my own purposes, the result of repeated tests under controlled conditions is enough to render it "fact" to me. Clumps kill my shots.

Feel free to conduct your own scientific tests, they're fun!


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## Dylan (Dec 5, 2011)

I was just being lighthearted/sarcastic, considering my earlier posts


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## jonathanhook (Apr 25, 2015)

shrink said:


> Scientific evidence is hypothesis, test, get result, repeat, get another result, repeat, get another result, until you have a statistic that is consistent enough to be considered fact. Don't confuse science for anything other than a series of proven theories.


That's the scientific method. Whether the scientific method = science, or whether it science is a broader term for the pursuit and understanding of knowledge is a bigger question. Social scientists who employ idiographic, rather than nomothetic, approaches might argue the latter, perhaps referring to the root of the word science in the Latin word for "knowledge". Wikipedia's page on science is pretty strongly aligned with the former!

Nevertheless, I think that we can agree that hypothesis testing is probably the best approach to follow if we want to answer questions about the way water behaves as it travels through coffee .


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## Mrboots2u (May 10, 2013)

I fail to see how ones of these could be a good thing in your ground coffee...


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## risky (May 11, 2015)

shrink said:


> MY SJ clumps a fair bit, even with doser modifications.


Curious, because mine doesn't at all. Do you prefer beans from the darker end of the spectrum by any chance?


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## urbanbumpkin (Jan 30, 2013)

urbanbumpkin said:


> From someone who used to own a Mignon, I found that clumps do exist and don't vanish with just tamping


I will re-iterate my point..... Flumps do exist and don't vanish with tamping.

I'm not 100% on Rastafarian's, I think they're make believe.


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## 7493 (May 29, 2014)

To qualify my vote, i.e. 'No' I suspect it depends on the quality of the clump. My 65e does produce clumps but the merest touch disintegrates them. I would have thought more integrated clumps may well affect distribution/channeling etc. (For completeness, our tastes are on the dark end of the spectrum.)


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## seeq (Jul 9, 2011)

Can we re title this threat to 'what is the meaning of science?' It would seem to be more fitting than the original topic.

Three pages on and nobody has really answered exactly what was asked. However in my honest opinion you don't really need 'scientific' facts and figures. Many people on this forum could be described as experts in this field and there is certainly enough collective experience to be able to answer pretty much any coffee related question. If the consensus on this forum is that clumps destroy shots then I have absolutely no doubt that it's true. I don't need facts and figures to back it up.


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## urbanbumpkin (Jan 30, 2013)

seeq said:


> Three pages on and nobody has really answered exactly what was asked.


....because they cause channeling and make shot taste not as good as they should?


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## Dylan (Dec 5, 2011)

seeq said:


> Can we re title this threat to 'what is the meaning of science?' It would seem to be more fitting than the original topic.
> 
> Three pages on and nobody has really answered exactly what was asked. However in my honest opinion you don't really need 'scientific' facts and figures. Many people on this forum could be described as experts in this field and there is certainly enough collective experience to be able to answer pretty much any coffee related question. If the consensus on this forum is that clumps destroy shots then I have absolutely no doubt that it's true. I don't need facts and figures to back it up.


The problem is, although there is a lot of collective expertise, there is very little actual scientifically based knowledge.

Every now and then, someone with the right machines at work gets to do some particle analysis, and those with a refractometer are able to inject some hard numbers into their extraction yeilds, but everything else is guesswork.

This has never in my eyes been better illuminated than when Colin Harman talked about 'pocket science' and how development of the Mythos One showed how the prevailing theories among the coffee 'experts' on why you needed to adjust a grinder throughout the day (when using in a shop) were largely incorrect.

But thats the whole idea of theories, you have them and then, if you really desire the correct answer you develop a scientific method to test it.


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## seeq (Jul 9, 2011)

I get that and there is a science behind the food and drink industry. There is a reason that Heston Blumenthal has a 3 star restaurant that for several years was best in the world, a mixture of science and experience to create 'perfect' food.

But it's still subjective. I could measure the Yield, etc and come up with a numerically 'perfect' shot. However some people will find it too bitter and some will find it too acidic.

Sometimes I think science can be an obstruction. How many threads are on this forum that request (for example) what extraction ratio is best to use. The answer is always the same 'whatever you prefer the taste of'

I think in some ways that can be applied to this topic. If, using your setup, you notice no difference in taste by breaking up clumps, then what's the point? Despite any scientific evidence that it makes a difference, if you can't taste it, is it worth doing?

On the counter, if you can tell the difference (I certainly can with my grinder) then I don't need any amount of scientific evidence to tell me that it's worth doing.


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## Jollybean (May 19, 2013)

My HG One doesn't clump at all but I have to stir the grounds to get a good distribution and central pour. Maybe stirring to break up the clumps just improves the distribution in the same way, so it is not the clumps themselves causing a bad shot but the action of stirring to remove them and redistributing the grounds in general that leads to a better shot?


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## Dylan (Dec 5, 2011)

Taste is king, that much is true. I have never concerned myself with extraction yield but in that case higher is always better is it not?

I think a lot of things, like clumping, are almost impossible to prove one way or the other, as has been said a few times on this thread there are way too many variables to say because clumping doesnt/does affect the extraction from one grinder it will/wont from another, and those grinders can be the same make and model, but just have a different environment, or differently aged burrs etc etc etc.


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## MWJB (Feb 28, 2012)

seeq said:


> But it's still subjective. I could measure the Yield, etc and come up with a numerically 'perfect' shot. However some people will find it too bitter and some will find it too acidic.


How many times have you done this? You're also misunderstanding the mechanism a little, if the shot was "numerically perfect" for that coffee/brewer/grinder (& the coffee is not out of the consumers typical range of preference) it would have been judged so by the taste regarding sour/bitter/sweet balance, then the number recorded. Aiming blindly for a number and then drinking all coffee at that number (there is no 'one size fits all number'), whether you like it or not, is not the aim of the game.

EY is objective, preference is more subjective, but if being unable to achieve a certain EY due to clumping/whatever preventing you hitting a high preference, then it's not so easy to separate the two?


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## jeebsy (May 5, 2013)

Dylan said:


> Taste is king, that much is true. I have never concerned myself with extraction yield but in that case higher is always better is it not?


Not really. Some grinders aren't really suited to push over 19%, others might taste 'under' at that level


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## Dylan (Dec 5, 2011)

I see, righto.


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## shrink (Nov 12, 2012)

risky said:


> Curious, because mine doesn't at all. Do you prefer beans from the darker end of the spectrum by any chance?


No quite the opposite, I prefer medium light. Nothing Darker than Rave Signature.


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## lespresso (Aug 29, 2008)

I can't speak about pump machines, but for levers clumping is a non issue. Tell me how after say 10 seconds of 1.3 bar pre-infusion that any clumps will exist, given that coffee grounds are hydrophilic and they expand when wet, pushing away from each other and in doing so destroying any clumps.

As you can see from the work on transparent portafilters on our site, even the idea that you are working with a solid puck of coffee is completely flawed the moment water arrives.

You will see that it is behaving much more like sawdust held against a drain that has too fine a mesh covering it by the water pressure flowing through/around it.

The moment the water pressure is reduced the coffee grains kick up like glitter in a fairy lantern - there is no 'puck'

Start thinking of coffee as sawdust in structure as it performs in a similar way in water, particularly for light roasts, rather than a non permeable material such as grains of rock or plastic.

You tamp the coffee to create a puck, and when you remove the PF after the shot you have a puck, but when the shot is drawn you don't really have a puck in the conventional sense - you have a collection of light fluffy grinds that will happily float off in all directions, but for the water pressure forcing them against the bottom of the PF.

If clumping is an issue pre-infusion has not completed prior to extraction pressure being applied.


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## lespresso (Aug 29, 2008)

Poor distribution is responsible for channelling. Clumping is not.


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## MWJB (Feb 28, 2012)

lespresso said:


> Poor distribution is responsible for channelling. Clumping is not.


How can you be certain they aren't inter-related? If your grind is very clumpy then it won't distribute well.


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## lespresso (Aug 29, 2008)

If you were to illustrate with a Venn diagram it is only where the set 'clumping' intersects with the set 'poor distribution' that channeling results where clumping is present, and it's a very small intersection, being only the most extreme cases imaginable quite frankly

As channeling results in the remainder of the set 'poor distribution' too it is poor distribution that is responsible for channelling, not clumping.

By way of illustration, the eureka mignon clumps like a bastard, so CFUK should be filled with owners complaining that it channels like the trevi fountain. It doesn't. It is one of the best grinders at that price point.


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## Mrboots2u (May 10, 2013)

lespresso said:


> If you were to illustrate with a Venn diagram it is only where the set clumping intersects with the set poor distribution that channeling results. As channeling results in the remainder of the poor distribution set it is poor distribution that is responsible for channelling, not clumping.
> 
> By way of illustration, the eureka mignon clumps like a bastard, so CFUK should be filled with owners complaining that it channels like the trevi fountain. It doesn't. It is one of the best grinders at that price point.


Most of em use wdt tho ....


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## lespresso (Aug 29, 2008)

I'm suggesting they might be able to quit the habit, at least if they have a lever


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## MWJB (Feb 28, 2012)

Might be interesting to find out how many Mignon users grind straight into the PF, tamp & pull vs those that redistribute?


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## jlarkin (Apr 26, 2015)

lespresso said:


> I'm suggesting they might be able to quit the habit, at least if they have a lever


If the Mignon and L1* Venn diagram is created, I guess you'd have to squint very hard to see the (an?) intersection

*other levers are available and some are even more affordable but that's not as amusing to me.


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## lespresso (Aug 29, 2008)

Who mentioned L1? It's got nothing to do with it. What I am saying holds true for any lever machine. Don't over think it.


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## Mrboots2u (May 10, 2013)

lespresso said:


> Who mentioned L1? It's got nothing to do with it. What I am saying holds true for any lever machine. Don't over think it.


Or machine with decent pre infusion


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## bongo (Apr 20, 2014)

MWJB said:


> http://www.tampertantrum.com/tamper-tantrum-lite-the-fumbally-colin-harmon/


So most of the debate has gone toward 'does clumping matter or not' - arguments on both sides, rationale on both sides, but most opinion votes opinions are still that it doesn't matter...

As to why clumping happens the only suggestion I've seen with any sort of 'evidence' is in the link above when the talk went toward exit speed.

To fast an exit speed = coffee everywhere

Too slow = clumping

Nothing mentioned with regard to static, oil or moisture... so possibly just down to grinder design, be that shute angle, burr set angle, motor power, rpm, again a whole host of variables that add to the problem, but possibly an easier one to 'test'....

Anyone got anything to add / contradict this?


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## MWJB (Feb 28, 2012)

bongo said:


> Nothing mentioned with regard to static, oil or moisture... so possibly just down to grinder design, be that shute angle, burr set angle, motor power, rpm, again a whole host of variables that add to the problem, but possibly an easier one to 'test'....
> 
> Anyone got anything to add / contradict this?


Target particle size, set your clumpy grinder coarse enough and you'll eliminate clumping...but then you'll also probably under-extract at typical espresso brew ratios. Perhaps grinders with a wider particle distribution, might be less prone to clumping?

Maybe the high exit speed sprays grounds out at high enough inertia to break static cling between each other, grinding the letting grounds collect in the chute allows them opportunity to bind together?

Also worth noting in the Harmon/NS presentation that he says, "with clumps you get uneven extractions".


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## coffeechap (Apr 5, 2012)

I am not entirely sure this is down to speed. The major for example has a high spin speed, you can still get it to clump, the royal has a slow spin speed, but clumps less than the major at a similar fineness. Although it has no scientific research behind it, I have notice differences when humidity is present the more humid the more liable to clumping a grinder is. The finer you grind the more liable to clumping, the smaller the exit chute to the grinder, the more likely to clumping.

Does it make a difference in the extraction, I belive that clumping will affect the distribution and distribution is the biggest factor in channeling, so does a clumpy grinder do a decent job (mignon)? The answer is yes, but you have to work so much harder for that perfect extraction.


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## bongo (Apr 20, 2014)

MWJB said:


> Target particle size, set your clumpy grinder coarse enough and you'll eliminate clumping...but then you'll also probably under-extract at typical espresso brew ratios. Perhaps grinders with a wider particle distribution, might be less prone to clumping?


agreed, but by grinding coarser my understanding is the exit speed also increases - perhaps hence no clumping?



MWJB said:


> Also worth noting in the Harmon/NS presentation that he says, "with clumps you get uneven extractions".


Indeed he does, but then he also believed that grinders ground coarser through the day - theory that he now refers to as pocket science as the theory was comprehensively dis-proven.

Perhaps the belief in clumping and uneven extractions is why he nor others here who believe in the clumping channelling theory have been a WBC? (said jestingly, tongue in cheek)


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## risky (May 11, 2015)

From the latest barista hustle:



> Clumps
> 
> Stop worrying. Poke one with your finger and it breaks apart instantly. Now think about how hard you're tamping. Now think about 110 pounds per square inch of water pressure. Is it still a clump after all that?


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## MWJB (Feb 28, 2012)

He also says:

"When distributing, the aim is for a perfectly homogenous and flat mass of coffee grinds: no air pockets, divots, cracks, slopes or similar nonsense. Now, I said perfect; not 'pretty good'."

...& shows a picture of a PF with clumps described as "not perfection".

If you have a very clumpy grind from a Rocky or Mignon, "perfection" is hard to achieve without measures beyond a tamp.


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## DoubleShot (Apr 23, 2014)

Using a high end grinder, you would ideally not want clumps nor be poking them!


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## shrink (Nov 12, 2012)

lespresso said:


> Poor distribution is responsible for channelling. Clumping is not.


I remain unsure on this one, at least from a pump machine perspective.

Today I pulled two shots back to back. 18.5g each.

First shot I ground, and did my normal stir and tap to break up and distribute evenly. The pour was even with a single central tail from the naked PF.

Second shot, I didn't stir, I just ground into the PF, and tapped gently to distribute evently. Pulled the shot, and about 4 tails came out of the naked PF, resulting coffee was decidedly more bitter.


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## jlarkin (Apr 26, 2015)

shrink said:


> I remain unsure on this one, at least from a pump machine perspective.
> 
> Today I pulled two shots back to back. 18.5g each.
> 
> ...


It might be a coincidence of wording but as far as I remember, bitterness is a sign of over-extraction - so maybe it demonstrates that it did work and you extracted even more than normal? It's also possible that isn't the case ...


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## shrink (Nov 12, 2012)

that's very much the point, bitterness comes from the fact that in areas of channeling theres an over extraction going on, but in the other areas of the puck, we're not extracting anything useful. SO you end up with more bitter flavours than you would from an evenly extracted puck.

Until I can justify / afford / win a better grinder, i'll stick to stirring out the clumps


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## MWJB (Feb 28, 2012)

jlarkin said:


> It might be a coincidence of wording but as far as I remember, bitterness is a sign of over-extraction - so maybe it demonstrates that it did work and you extracted even more than normal? It's also possible that isn't the case ...


Bitterness can be overextraction, but can also be related to under-extraction and channelling/unevenness, or even nominal extraction at a more bitter level, prior to sweetness.

Sourness is more usually indicative of under-extraction, but bitterness harder to pin down to a single diagnosis.


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## h1udd (Sep 1, 2015)

When I first started trying to reach coffee nirvana I used to dose into a cylindrical container mounted in my PF and then stir it around with a tooth pick, then remove the container and smooth it out and give it another stir to break it all up, then tamp and polish, and (ok lying now) with to a buffed tamper to polish even more, then with to my polishing tamper made from pure virgins thighs etc etc ....... most of the time the time the pull was good, only channeling when doing the first couple of shots of the day and needing to adjust the grind.

these days I just grind and tamp .. with a little polish .... and most of the time the time the pull is good, only channeling when doing the first couple of shots of the day and needing to adjust the grind

So in my book, clumping makes sod all difference to the shot or the taste

BUT !!!!!

clumping is a pain when trying to evenly fill a basket from a doserless MC4 ... and as the clumps build theistic together and then it overflows instead of filling evenly, meaning I have to jiggle it or poke it ... and that makes more mess ....... so a no clumping solution from the grinder by super polishing the chute etc, does make a difference .... just not to the drink, but to the state of my table


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## shrink (Nov 12, 2012)

are you using a naked PF?

are you able to see the extraction while its happening to know you're not getting channelling?


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## MediumRoastSteam (Jul 7, 2015)

I've got an Eureka Mignon. It is just a clump monster. I used to grind straight into the PF, nutate and that was it. As far as I knew, I had 15g in, 30g out in 30s. That was until I bought a new machine and a naked PF, and I could see what was happening: A dead spot in the centre, very slow to come through, and it will just channel towards the end. So I decided to to re-learn everything again, and this is what works for me, after going through the Home Barista Espresso 101 videos and gathering information from posts in this forum:

- Removed the spring from the PF;

- Dose into the basket outside the portafilter, rotating the basket as I grind to the required weight, so the grounds are evenly distributed at the bottom to an extent;

- Two vertical taps, two horizontal taps (one on each side);

- Using a toothpick or other similar device, I just make sure the surface of the coffee is even, and there are no gaps, specially towards the edges, and if flat;

- Gently level tamp;

- Tamp firmly;

- Put the basket into the portafilter;

- Lock and pull.

It makes a great difference, and I can see my extraction coming out really nicely, evenly, in one stream. I did also notice the difference in taste; It is so much better.

The only thing I would like to try to eliminate would be to be able to dose straight into the basket inside the PF, thus making easier to dump the spent puck.


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