m03ppp wrote:Perhaps I'm wrong but afaik there is no research on that subject (or do you know any?) and he is not alone, both James Hoffmann and Scott Rao have expressed similar thoughs.

http://www.jimseven.com/2011/02/08/cont ... profiling/
http://www.jimseven.com/2013/08/21/alri ... k43s-then/
Scott Rao Espresso Extraction: Measurement and Mastery

Edit: Added another link.

Not peer reviewed.

None of these people are actually lab testing their grinders. Fines are mostly bound to the coarse particles and only release when put into liquid or blasted in air jets. Getting a "fines free" sieving grind means very little, since even the shaker table sieves only shake loose the dust, not the bound fines. There are a half dozen articles by Petracchi that describe this, and the results are summarized in the Illy book, and probably on the new site.

Sieves are useful for determining the mean size of the coarse particles (Using the sieve for the 50% point for your particular grind setting). They are marginally useful for getting a more accurate distribution of coarse particles (use a shaking table and a gradated set of sieves). They do not work at all for estimating fines.

So let me repeat the actual laboratory sciene for the umpteenth time:

• Espresso is defined by the fact that the puck regulates the flow, and that both the extraction and the flow rate are determined by the particle distribution.
• Fines amount to less than 0.25 percent pf the weight of the ground coffee. No matter how they extract, they have no noticeable effect on taste. The people who have "tested" this have done so knowing what they are drinking, and are hallucinating to taste whatever the currently fashionable group-think wants
• The flow of espresso depends very sensitively on how the fines interlock with the coarse particles to cement the puck into a resistive medium. This is so dependent on particles shapes and other minutia that even the best lab equipment is stymied with characterizing it precisely (apparently this is nothing unusual when it comes to material aggreggates). However, it is easy to see that large conicals do better in producing flow consistency than most other grinders
• A second aspect of extraction is the uniformity of the coarse particle sizes. In this, large flat burrs measure up better than other grinders. In our testing during the TGP, the added flow consistency of large conicals outweighed the added extraction uniformity of larger flats; but this is a result that could easily change with new designs
• It may be that very large brewing grinders, when set up for espresso, have fines that pack consistently enough so that their added coarse particle uniformity shows up. But it is b*llsh*t to claim that they make better espresso because they produce no fines, since a no fines grind cannot block the flow in an ordinary espresso basket.

I will add that there is now a group of about ten or so well known coffee people, mostly trying to make a living as consultants and salesmen of overpriced accessories, who are fabricating a growing amount of nonsense about espresso and coffee. I hope that they are merely disgracing themselves and conning a few people out of a few bucks; and that it doesn't get tot the point where people actually spoil the coffee they make.

happycat wrote:Maybe time to reread Thomas Kuhn?

How could I have missed it? All these years I though you need the cement of fines to seal the coarse particles. I never suspected that coarse coffee particles had a zone of rubbery, self-sealing space/time around them that was modulated by the grinder's burr design. Clearly, fines are just as much of a myth as ether.