Normalization Quality, Grinders and Coffee Grinds

Grinders are one of the keys to exceptional espresso. Discuss them here.
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AssafL
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#1: Post by AssafL »

My first ever post on H-B dealt with grind distribution improvements: Mazzer Mini E - Grind distribution improvement mods. While hacking away at the Espresso machine did improve the results as well - every major stop along the way to coffee improvement had to do with the grinder, looking at grind speed and static: Static and grind speed and grinder alignment: Aligning the Versalab burrs and so on...

With the kind help of grinder illuminati like Frank (Terranova) and NickW and many others my Espresso was improving considerably: both subjectively (flavor, bouquet, texture) and objectively (EY).

But why? And why could some even get a decent cup at 24% EY (not me - others - perhaps with EK43 and other Titans)?

Earlier this month Keno posted a link to a new book: The Craft and Science of Coffee book. In it one particular quote has been keeping me awake, it is from chapter 13 - The Grind - Particles and Particularities written by Martin von Blittersdorff from CAFEA and Christian Klatt from Mahlkonig:
3.3 Postprocessing: Normalizing, Compacting, and Classification

A normalizer is an integral part of an industrial grinder for Turkish through filter fine R&G coffee. Just below the outlet of the grinder, in a cylindrical tube, the coffee is further processed by powerful mixing, kneading, or beating with paddles or hammers, respectively. On one hand, this aims at further comminuting the big particles and, most importantly, cutting of the chaff or silverskin from inside the fold of the coffee beans that had been released during grinding. During mixing, the silverskins are colored brownish and become rather unremarkable in the R&G coffee. On the other hand, the fines shall be reduced through forming agglomerates or through their adhering to bigger particles when hitting each other.
I always had the sense that of all the "good" grinders - the better ones excel in creating a uniform distribution of density in the puck. How they did that was a mystery to me. The concept of normalization makes a lot of sense.

For most of us H-B'ers Normalizers would come in all shapes and forms: the doser, the Versalab "scraper", the Mazzer "chute" and the LWW "Shaker" (as was my first post's "La Maccina Fluffinata"). For those of us who end up with a bad implementation of a normalizer WDT comes to the rescue (thank you Weiss).

Of particular interest was the last line in the paragraph about the reduction of fines by "forming agglomerates" and "adhering to larger particles". Which to me popped up the following hypothesis:

Proposed hypothesis: What if the real reason that bigger or slower burrs with good normalizers result in higher EY without bitterness is their success in affixing fines to larger particles?

Doublehelix labelled this hypothesis rather creatively as the "fractal" hypothesis - that good grinders result in pucks that are actually of homogenous density with ever finer powder "clinging" and held in place by larger particles (rather than "clumped").

Could this hypothesis explain:
1. Why larger burrs work better? (perhaps it has more real-estate to "roll" boulders in fines?)
2. Why slower grinding works better? (perhaps it leads to more time for the particles to bang against each other?)
3. Why "fluffy" grinds pull better? (a pull from a fractal distribution of particles)
3. Explain why every Nespresso capsule will pull identically while aftermarketer filled capsules fail? (better normalization)
4. Why espresso burrs have slits? (It may not be a slit for the boulders - may actually serve to catch fines until a boulder sweeps them away)

I have no clue how to test the hypothesis - but I thought I'd share it so that the wiser and more experienced would find the loopholes...

NB - Would the correct term for this be tortuosity? Would a better grinder homogenize tortuosity?
Scraping away (slowly) at the tyranny of biases and dogma.