Zephyp One way to look at it is that a filter paper is like a net, the coarser the weave, the more particles that will pass through, so grinding coarser helps mitigate particulate getting into the drink (you can clearly see what I’m talking about if you look at a metal. permanent filter). I haven’t any means of analysis for filter paper porosity, but I’d guess the Hario med crepe have generally smaller pores, than the Rombouts?
If you take the 5 grinds above (for Hario Med Crepe, 40g/40s), the variations (stdev/avg) at Kruve intervals are as follows:
400 19%
700 15%
900 14%
1100 25%
1200 33%
1400 55%
…so the smaller end is generally more consistent between grinders than the larger end of the distribution, but the middle seems even tighter. Doing a rough, ‘back of a fag packet’ analysis the d16 (16% mass) variation is around 9%, d50 around 6% d84 around 11%.
The variation in grind distribution Q factor (square root of the span +/- 1x stdev) is only 3%. Avg Q factor is roughly 1.56.
So basically, the differences in avg grind size seem fairly small, as does the difference in grind size distribution quality (Q).
The 2 grinders that scored lowest, to my preference, are those that ended up being set to the coarsest grind, rather than having similar Q values.
Yes, there was a video of the 40g/40s method, but I pulled it, along with a bunch of other V60 videos as they had no ongoing value, following the withdrawal of the Hario med crepe papers.
