How do I adjust the grind size for optimal espresso extraction

To achieve optimal espresso extraction, grind finer when aiming for sour or under-extracted shots and coarser for bitter or over-extracted ones. This is because a finer grind allows for better water flow and dissolves the coffee's surface compounds more efficiently, resulting in less extracted solids and a cleaner taste. Conversely, a coarser grind impairs this process, leading to bitter flavors from unextracted solids. Experiment with your grinder and adjust the setting according to your machine's portafilter size for optimal results. For most home espresso machines, a grind setting between 1:15 and 1:17 (coarse:fine) is usually suitable. Keep in mind that grinder quality, machine type, and coffee beans also play significant roles in determining ideal grind sizes.