The effect of clumping on espresso

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TheodoricOfPuck
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#1: Post by TheodoricOfPuck »

I am curious about the effect of clumping on espresso. What we effectively do is create one big clump in the portafilter, yet clumping of some of the coffee that goes in to that big clump is said to degrade our result. Does anyone know of any studies that take object measurements like flow rate, channeling percentage, components of resulting coffee that show the effect of clumping? I hoping to avoid a discussion on whether clumping matters, I'm only interested in objective information that does not include subjective analysis like tasting.
Thx.

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Jeff
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#2: Post by Jeff »

I don't know that there is anything dealing with theory or practical measurements of non-uniformity in the puck on a macro level. There have been studies involving the impact of various WDT techniques (including "none") by people like Stéphane Ribes, who allowed it to be re-published here Puck prep study. Some of the mechanisms that may associated with the fall-off of extraction yield ("EY") are put forward in https://pubs.aip.org/aip/pof/article/35 ... ee-brewing. Johnathan Gagné's The Physics of Filter Coffee may have some insight.

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Jaroslav
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#3: Post by Jaroslav »

Have a look at this short post:

Simple Clumps and WDT Test: Espresso
Jaroslav

Nunas
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#4: Post by Nunas »

My ZF64w produces some clumps. My Sette 270w does not. I don't do anything different in terms of puck prep between the two. I don't detect any consistent differences.

boren
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#5: Post by boren »

@Nunas - do you WDT?

Nunas
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#6: Post by Nunas replying to boren »

No, I don't do anything much anymore, although I've tried nearly every gimmick. I grind the coffee straight into my portafilter, give it a few vertical thumps on my tamping stand, rock the tamper in a little circle (nutate), and lightly press (maybe only about five pounds or so), ensuring that the puck surface is dead flat. I have a group head manometer and can see if anything is going wrong, such as channeling; it rarely does. In recent years, the only gimmick that I've found to be effective is a sintered metal (IE the thick kind) puck screen. Although it does not seem to make any discernible difference in the cup, it most certainly keeps the group much cleaner.

mathof
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#7: Post by mathof replying to Nunas »

I find that most of the "gimmicks" only apply to very lightly roasted coffees. What do you use in your gimmick-less routine?

Nunas
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#8: Post by Nunas replying to mathof »

I roast all my own coffee. I drop halfway between the end of 1c and start of 2c. So, mostly medium roasts.

bullet08
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#9: Post by bullet08 »

Simple physics. If there is dense area in the puck, compare to the surrounding area, water will go around it. What more studying do you need?

buckersss
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#10: Post by buckersss replying to bullet08 »

Can you say that clumps always create dense puck areas?

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