Grinding coffee bean-by-bean is often compared to cryogenic grinding, double grinding, and re-processing as types of impractical perfectionism—generally deemed unsuitable for commercial settings, as outlined by Scott Rao in The Professional Barista’s Handbook. Wet grinding remains a concept rather than a reality, a dream of early third-wave enthusiasts, but let’s include it for discussion. Cryogenic grinding does exist, but here we will explore a practical application for bean-by-bean grinding.
The most thorough examination of bean-by-bean grinding was conducted by astrophysicist-turned-barista Prof Jonathan Gagne. As outlined by Scott Rao in The Professional Barista’s Handbook, a few years ago, some of his followers expressed concerns about the impact of single-dose grinding (where a pre-weighed dose of beans is placed into an empty grinder hopper) on grinder performance compared to using a full hopper. Jonathan demonstrated that while there is a difference, it might be negligible; specifically, only a few beans at the end experience the so-called popcorn effect, resulting in a slightly coarser grind.
There are two terms you need to know before you read any further.
Popcorning
When coffee beans are driven through the rotating grinder burrs, they must navigate through whatever gaps present themselves between these burrs which aren’t already occupied by other grinds moving through the system. In contrast, the behaviour of a solitary bean in an empty hopper is markedly different. Without the collective pressure of other beans, a solitary bean bounces around haphazardly, sometimes slipping through largest gaps at the edges of the burrs known as the tertiary cuts. Single beans also tend to bounce around at the entrance to the blades, resembling popcorn kernels popping and jumping in a hot pan, which is why it is aptly named “popcorning” or “the popcorn effect.”
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