Grind Size

What is grind size? It is the measure of how coarse or fine your coffee beans are ground. This variable is arguably the most important tool a barista has for controlling the rate of extraction. When water hits coffee, it extracts soluble compounds from the surface of the particles. Smaller, finer particles have more surface area, which allows for faster extraction, while larger, coarser particles have less surface area, leading to slower extraction.

Why does grind size matter? It is the primary mechanism for balancing the flavor of your coffee. If your grind is too fine, water will extract too much from the coffee, leading to over-extraction, which is often perceived as bitter, astringent, or hollow. If your grind is too coarse, water will pass through too quickly, leading to under-extraction, which often tastes sour, salty, or thin. The goal is to find the grind size that allows for an even, balanced extraction where the sweetness and acidity are in harmony.

Different brewing methods require different grind sizes. Espresso requires a very fine grind to create the resistance necessary for high-pressure extraction. French press, which relies on immersion, requires a coarse grind to prevent the coffee from becoming muddy and to allow for easy filtration. Pour-over methods typically fall somewhere in the middle, depending on the specific device and the desired contact time.

In practice, grind size is the variable you will adjust most frequently. As coffee ages, its moisture content and structure change, which may require you to adjust your grinder settings to maintain the same extraction quality. Investing in a high-quality burr grinder is essential because it produces a uniform particle distribution. If a grinder produces a mix of very fine 'fines' and very large 'boulders,' the coffee will extract unevenly, making it nearly impossible to achieve a clean, sweet cup. Mastering your grind is the first step toward professional-level brewing.