How does grind size affect espresso extraction?

The correct understanding regarding the impact of grind size on espresso extraction is that finer grinds lead to a greater surface area being exposed to water. This increased surface area allows for more efficient extraction of the coffee's flavors and compounds during the brewing process.

When coffee is ground fine, water passes through it more slowly than it does through coarser grinds. This slower passage allows for a more even and thorough extraction of dissolved solids, oils, and other flavor compounds, resulting in a fuller-bodied and richer espresso. However, if the grind is too fine, the extraction can take too long, leading to over-extraction, which can produce a bitter or unpleasant flavor in the final cup.

Understanding this balance is crucial for achieving the desired flavor profile in espresso. While finer grinds might enhance extraction efficiency, there's a fine line between optimal extraction and over-extraction, which is why the effect of grind size is key in dialing in espresso shots.