Grind Mechanics and Uniformity
Lance Hedrick claims in one of his latest videos that a coarser grind setting generally produces more uniform distribution. Why is that?
Every time a piece of coffee hits the burrs to get ground, it makes some fines as the whole bean or larger ground essentially explodes or shatters kind of like glass when it hits the burrs. You get some pieces that are about the size of the gap between the burrs, and a lot of pieces that are very, very small (the fines). The finer your grind setting is, the more times you have pieces of coffee hitting the burrs (as bigger pieces that have already been created from the whole beans will hit the burrs again to get made smaller), so more fines are produced. So the finer you grind, the more fines you get.
Grinders and Extraction
Extraction is the process of water removing the soluble material from the coffee grounds to give you your finished beverage. If you don’t extract enough soluble material, your coffee will be weak, watery, sour, vegetal, and/or underwhelming. This kind of brew is commonly referred to as “underextracted.” If you extract “too much” (this is in parenthesis for a reason - keep reading) soluble material, your coffee will be harsh, bitter, and/or astringent (mouth-drying). This kind of brew is commonly referred to as “overextracted.” If you extract the right amount of soluble material, your brew will be balanced, sweet, smooth, and full of origin character (perhaps fruity, perhaps floral, perhaps savory, etc).
