Why does grinding coarser create more fines?

(John) #1

I’ve read this Baratza blog multiple times and am struggling to understand this statement:
“there are proportionally more fines at coarser settings, which leads to a coarsening adjustment, which leads to more fines…”
Why is this? Intuitively I would think that the smaller the gap between burrs, the more particles would be smashed by them, leading to more fines. But Baratza is saying that coarsening will lead to more fines.

(Mark Burness) #2

As you go coarser the fines get proportionally bigger (as do the largest particles), but particles below, say 200um for purposes of illustration, will reduce. A grind size isn’t dictated by the largest grind size at all, this is wrong. The largest grinds will be a tiny minority, as will a similar proportion of the smallest. The average size of particle, by weight (not particle count, nor surface area), will be a little under the mid point between largest & smallest particles.

Baratza hasn’t released any grind distribution data yet for the Sette.

Luckily, small drip brews can be made with a range of grind sizes. If you have to brew with a grind on the finer side, keep agitation down (after pre wet) & add brew water relatively quickly in just one, or just a few pulses, which seems to be basically what they are saying. You may find yourself limited to brews under a certain size.

(John) #3

Thanks Mark. If I’m reading your response correctly, you’re saying the opposite of what Baratza is saying. They say that coarsening leads to more fines while you’re saying that it will actually reduce fines (which intuitively sounds right to me). Am I reading yours correctly?

(Mark Burness) #4

Short answer, yes, I am contradicting them. But it depends on your definition of ‘fines’.

Within reason, over a range of settings it’s likely that the proportion of the grind (by weight) that is half the size, or twice the size of the average, will be fairly constant if your definition of fines is relative to the average. Let’s say your grind size is 500um average, then the smallest 2.5% (as an example, not meant as definition) might be from 1um to 250um. If your grind size is 1000um average, then your smallest 2.5% might be more like 1um to 500um. By weight, the same proportion, but in size they cover a bigger span.

If your definition of fines is particles under specifically 50um, or 70um, or 125um, then these will usually become less, as a proportion of the total ground weight, as you grind coarser.