The complexity of grind size distributions that we discussed in Lesson 1.03 explains why it is so difficult to replicate the desired grind size on different equipment. Even grinders of identical models at identical settings will produce slightly different grind size distributions, thanks to small differences in alignment or wear on the burrs, for example.
For this reason, replicating recipes across two different sets of equipment (for example, in two cafes in the same chain) is not always straightforward. Using the same numerical grind setting, even on two apparently identical grinders, will not produce the same results.
It’s possible to communicate a target grind size by using a proxy measurement such as shot time, but even this has limitations. For example, a particular espresso recipe using a Mahlkoenig EK43, a recipe that tastes great on a well-aligned grinder, might suffer from underextraction flavours or even be impossible to achieve on a grinder that is less well aligned.