People in the Tang Dynasty had a saying of "three boils of water" when making tea: the first boil, "boiling like fish eyes, with a slight sound"; the second boil, "the edges are like springs with beads"; the third boil, "boiling waves and drums" ". Tea should be cooked when the water has just boiled for three times; if it is boiled again, "the water will be old and inedible." (See "Tea Classic: Five Boils"). Freshly boiled water is called "first boiling water". It is too tender and not powerful enough to make oolong tea. You can't boil it for a long time before using it. That way the water is called "three boiling water" and it's too old. It is best to use "double boiling water", that is, water that boils like a spring but not like a roaring wave.