3- Surface Area and Agitation:
For an interaction to occur between water and coffee, there must be contact between the two, and the contact varies based on the available surface area. The finer the coffee grind, the larger the surface area, because this increases the surface-to-volume ratio. The smaller the particle size, the higher the proportion of dissolved solids in the extraction process.
Therefore, the grinding process is of paramount importance in coffee making. It is also essential that all coffee particles are of uniform size for an even extraction process. If they are not, larger particles will extract fewer dissolved solids than smaller particles, leading to different extraction rates. This will result in both over-extracted and under-extracted dissolved solids in the same cup of coffee, which will not yield a satisfactory result or taste.
