PPM
Parts Per Million (PPM) is a unit of measurement for the concentration of minerals and impurities in water, with 1 PPM equivalent to one part of impurity in one million parts of water. The ideal coffee brewing water usually has a mineral concentration of 50-150 PPM.
PPM is used to assess the level of dissolved substances in water, which directly impacts coffee extraction. If the PPM is too low, the water lacks the ability to extract flavors properly, resulting in a weak, overly acidic cup.
On the other hand, excessively high PPM can lead to over-extraction, making the coffee taste bitter, astringent, and losing its flavor balance, especially the natural acidity.