The purpose of grinding coffee beans is to enable the water to remove (extract) the solubles (flavor compounds, oils, and solids) that create the flavor and body in coffee. The grind, or particle size must be matched to the brewing method, and the particle size must be as consistent as possible. The particle size (aggregate size) is extremely important to successful brewing. Don't be mislead by the popular belief that a finer grind will give you more flavor. The finer you grind coffee, the more particle surface area in relation to particle mass is being exposed to the hot water. The finer the grind, the more rapid the extraction. Over-extraction means you get too much, both what you want and what you don't want! The aggregate size must be matched to the brewing method being used, and the brewing time must be correct. Using an "espresso grind" for a drip brewer will slow the flow of water through the aggregate, and would result in a badly over-extracted and bitter infusion. If the grind is too coarse, the water flows too rapidly, and the resulting infusion will be under extracted and watery. The grind size for the press method is larger than the flat drip / gold filter size, and you generally have to use twice as much aggregate as with the drip method. You'll have to experiment to determine how much sediment you can tolerate in your coffee. The grind size has to be increased to eliminate sediment. The goal is an 18% to 22% extraction rate from the coffee particles. We provide a Grind Size Calibration graphic to help you set your grinder for the correct grind.