Wait, doesn’t boiling make water softer? Usually, yes. But if you boil hard tap water and let the sediment settle, you can pour off the top layer and leave the minerals behind. (Counter-intuitive, right?)
However, if you add minerals before boiling, like a pinch of baking soda, the evaporation concentrates the hardness. Let the water cool, and you’ve got a higher mineral content. (It’s like reducing a sauce, but for water.)
This method is for desperate times—like when you’re camping and the local water is suspiciously soft. Boil it, add a dash of salt, and pretend you’re fancy. (You are fancy. You’re reading an article about water hardness.)
