What Affects The Ideal Grind Size?
First of all, personal preferences will always determine the ideal coffee recipe. So too will the coffee you’re brewing: depending on the origin, variety, processing method, roast profile, and more, you may want to highlight different characteristics. Dark roasts, for example, are more soluble and so you might use a slightly coarser grind.
However, two points deserve special mention. The first is brewing method: different brewing devices are suited to different grind sizes. A French press, for example, is typically paired with a coarse grind. Most pour overs (one exception being the Chemex) lend themselves to medium-fine grinds. With espresso or Turkish coffee, you’ll want to go fine and extra-fine respectively. And some brewers, like the AeroPress, can suit a wide range of grind sizes.
Then there’s the age of your coffee. Hopefully, you’ll always have fresh beans to hand but, as the days pass since they were roasted, you’ll want to tweak the brew recipe. This is because the coffee’s flavors will fade over time. In this case, many home brewers and baristas like to grind finer; others prefer to up the coffee dosage and grind coarser to compensate. The first option will increase extraction; the second, intensity.
Yet even while controlling grind size opens up the door to manipulating coffee extraction – and therefore coffee flavor – there are also several things that can make it difficult for baristas and home brewers to do so.