Grinding By Touch
If you are looking for a better cup, one of the most important factors is "grind" or particle size. The smaller the grind, the more surface area is exposed and available for extraction. The larger the particle size (the chunkier), the less surface area is available for contribution of tasty organoleptic solubles to the cup. The relationship is exponential, and therefore, important to get right. In the lab we use either a particle analyzer ($$$) or a more affordable Rotapp (shaking nest of progressively smaller resolution sieves) to determine the actual particle size, typically expressed in microns - no two grinders are alike: if you place two models of the same grinder, one serial number apart, next to each other, there is a good chance that on any given setting, the particle size will not be the same between the two machines. Do not be unduly stubborn about the grind setting ("on a Brand X Model 123 you should use #5 for Chemex"). This approach is not reliable. Trust your palate, and make adjustments to taste. (We are oversimplifying a bit, as, particle size is only one of dozens of contributing factors, such as water composition, water temperature, mass of grinds, shape of grind bed, gradient (filter) through which water and solubles pass [porosity, flow rate, topology, etc.], turbulence of water hitting the grinds, topology of the grinder blades/burrs, volume of water (as ratio to mass of grinds), and so on and so on. So, assuming you are using good parameters all around, you should grind for taste - avoid the temptation to grind finer (the cheapskates approach), or to use more beans (in search of more body - wrong!); in the former approach, you will overextract and introduce bitterness into the cup (secondary organoleptics); in the latter case, you will achieve greater than optimal solubles extraction percentage (say 19%), and lose clarity of the cup, resulting in a muddy cup with little or no cleanness and definition to the potential taste profile. Be careful here - proper extraction will not make bad beans taste better; in fact, it will make bad beans taste worse. No cup can taste better than the beans (and water composition, and water temperature, etc.). A typical pourover (Hario or Chemex) works well with a grind size that feels like coarse sand when rubbed between your fingers - not chunky, and not so fine that it leaves residual dust in your fingerprints; we like the ration of 0.066:1 coffee:water by weight, so, for example, if you want to brew 16 ounces of coffee, grind 33 grams of beans and pourover 500 grams of water. Adjust your grinder to taste one notch at a time. It should take no more than 4 minutes to complete your brewing process (longer for larger volumes and vice versa); approximately 98-99% of the extraction of favorable solubles will complete within 1.5 minutes from the first splash of water.