Denis wrote: I have friends in my group of coffee geeks, that do comparision tests side by side with grinders, and with 2 grinders (ek43s with ssp aligned and Honne grinder) even with sieving the grind from both grinders with a Kruve after you obtain the same dose in the same range interval, lets say 250 to 600 um, using the same coffee dose 15 g with the same time and the same extraction and temp, Duomo distribution wich is the same each shot, you get different tasting coffees. WHY?

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Every coffee bean is different?

another_jim wrote:Um,, the ridges in the burrs criss-cross like scissors, pushing the beans into the narrowing gap between the valley of the burrs, where they are crushed. If the burrs are very dull, they no longer push the beans efficiently, and these remain at the same radial position in the burr, vibrating around, heating up, and slowing down the grind time. Presumably, this also produces more fines without splitting the existing particles into smaller coarse ones.

I know the scissor theory is the prevailing point of view, but in observation, it would appear they are more like breaking rocks than a shearing action.

Another random bit of data:

Same beans at room temperature (70f) vs. pre-warmed to 115f.

The pre-warmed beans allow for a much, much finer grind for the same dose and flow rate, or conversely, flow very much faster at the same grinder settings.

It's amazing to me how little about grinding coffee beans is actually KNOWN!

well, its quite a known fact that increasing temperature produces softer bean cells resulting in more elastic deformation during the grinding
as well as it is clear that grinding process is in fact gradual crushing of beans.

it is no freakin' tomato or butter to be sliced, dude
it's bloody stone of a friut

just try to "slice it" with you knife, end of discussion.

nuketopia wrote:Another random bit of data:

Same beans at room temperature (70f) vs. pre-warmed to 115f.

The pre-warmed beans allow for a much, much finer grind for the same dose and flow rate, or conversely, flow very much faster at the same grinder settings.

Also, I experience a much consistent (less fines) grind when beans are frozen. As a of matter fact, I use frozen beans 99% of the time. I believe Matt Perger also experimented with this and his conclusions were similar.

@kolu, there is no end of discussion.

Here is a coffee bean I cut with a knife 5 minutes ago just for you. As you can see, there are chunks that obvious have cutting and crushing marks on them. The half coffee bean has a clean cut on it. So you say coffee beans are not cut, are crushed? Before doing this kind of 100% affirmation at least try to cut a bean of coffee yourself with a knife.







On this image, A is with room temperature beans, B is with same beans but frozen.

Seriously, there's people who think frozen beans will produce less fines than room temperature ones?

I found the Grinder Paper published in Barista Hustle, it discusses the impact of grinding frozen beans and concludes the following:

"Heating the beans to achieve consistency pushes the beans above the shatter transition temperature and significantly reduces the total surface area (read: less and less-even extraction).
More cold = finer particles = more surface area = higher extraction. Lower temperatures could also mean less evaporation/sublimation of aromatic compounds (aroma loss).
Keep your pre-weighed doses in the freezer for higher, tastier extractions (though make sure they're sealed without too much moisture or any oxygen)."

So it seems that frozen beans break more evenly in finer particles...

Here is the paper: https://baristahustle.com/blog/the-grin ... explained/

I always thought it weird that he drew that conclusion, yet did not actually grind any beans that had been pre-warmed in the experiments. They did room temperature, frozen, dry ice and liquid nitrogen.

From which, he drew this completely unsupported conclusion?

I dunno, I've done the pre-heat trick and found that there is considerable difference between room temperature and heated beans.

The developers of the Mythos One Clima Pro (which intentionally pre-heat beans prior to grinding) did so for the exact opposite reason. I do remember a lecture where they had come to a different conclusion and measured data. I don't have a link though.