Your windows and mirrors are actually telling you a story. Next time you wash a glass dish, let it air dry completely without wiping it.
If you see white, chalky spots or a hazy film, that’s calcium carbonate residue left behind when hard water evaporates. It’s the same stuff that builds up in your coffee maker and kettle.
Fun fact: in some ancient Roman cities, they actually celebrated hard water deposits on aqueducts as a sign of purity. Today, we just call it “the scourge of sparkling clean dinnerware.”
A Guide For How To Test Water Hardness – JFFA
