As baristas, we’re used to discussing grind size on a regular basis, adjusting the grinder to produce finer or coarser grinds throughout the day to keep to the shot time in our recipe as the grinder heats up or cools down. However, when grinders heat up, the aperture between the molino doesn’t seem to be changing – which means the nominal grind size hasn’t actually changed. Instead, the grind size distribution has changed. Understanding the concept of grind size distribution is key to understanding some of the more recent developments in espresso making.