What should 'unimodal' style filter grinds look like to the naked eye?

Grinders are one of the keys to exceptional espresso. Discuss them here.

#1: Post by cactus_farmer »

Does anyone have a picture of a unimodal filter grind?

If the burrs are meant to be unimodal, should each grind basically look identical to the other, in size and shape, or is inevitable that no matter how 'unimodal' the burrs are, at coarser grind settings with light roasted beans that you will get the occasional oblong grind that looks a bit bigger than the rest of them?


#2: Post by Jonk »

cactus_farmer wrote:should each grind basically look identical to the other, in size and shape
No. The burrs can't control how the beans shatter, many pieces will be smaller than maximum size that is able to escape through the burr gap.

This picture is from https://coffeeadastra.com/2020/04/02/wh ... pour-over/ of coffee ground with SSP 'Ultra Low Fines' in an EG-1.

With flat burrs and a coarse enough setting there will always be oblong pieces. Ghost burrs and conical grinders will produce more spherical shapes with the same burr gap. There are no truly unimodal burrs and even sifters have the same problem that quite different shapes can pass through the same hole.

Team HB

#3: Post by ira »

From memory, something like a can of Yuban is probably about the best grind uniformity you'll ever see. In some ways, they probably have better QC than anyone in the world of coffee we inhabit and their customers expect every can, every year to be exactly the same. They use roller grinders that are likely bigger than your car run by 50HP or larger motors with water cooled rollers so that everything stays the same.