If your freshly brewed coffee has a sour, acidic tang, you may wonder if there’s something wrong with the coffee quality or water. Chances are, it's the grind size of your beans.

Finding the best grinder setting for your coffee depends on your machine. An espresso machine requires much finer grounds than a French press, moka pot, or drip coffee maker.

For example, making cold brew coffee is on the very other end of the spectrum and needs a much coarser grind size that will produce a texture similar to that of rock salt.

Sourness is typically the result of using coffee beans that are coarser than required, like using grounds meant for cold brew makers in an espresso machine instead, for instance.

Coarser beans require more time for the water to extract flavor. Using them in the wrong equipment may result in an under-extracted, acidic, and unbalanced brew.

The quantity of water used, its temperature, and the brewing time can cause over-extraction. Sour coffee can also be caused by over-roasted beans and inadequate gas dissipation.