Grinding is the act of breaking coffee beans into smaller pieces by increasing the surface area of the coffee, It is the means by which we are able to extract flavour (and caffeine) from a coffee bean. As such, the grind size has a huge impact on flavour when brewing coffee.
The finer the grind, the greater the exposed surface area. This means that when brewing coffee, a finer grind requires less water contact time whereas a coarser grind needs longer contact time. Hence why espresso coffee is a finer grind than say a French Press.
However, if the grind size is too fine it can produce an over-extracted cup of coffee leaving a bitter taste in your mouth. On the other hand, if the grind size is too coarse your coffee will be under-extracted and will have a sour or salty flavour.
To optimize the flavour of your coffee, each brewing method requires a different grind size. So, next week we will talk about Brewing Methods.