Many people wonder what hardness is in water. It is the dissolved minerals of calcium and magnesium formed by ionic reactions resulting in the formation of an insoluble precipitate. Thus, a precipitation test.
Unfortunately, that hardness is invisible to the eye. With this test, you will be able to visualize the hardness (calcium and magnesium). Once you see it, you will understand why it is a problem for any water appliance (wash machine, dishwasher, coffee maker, water heater, etc.)
Take a look