Take a white paper towel, fold the paper towel twice, and then take a drop of wine on the paper towel. The paper towel will infiltrate the water, the pigment will remain on the surface of the paper towel, and the edible alkali will be used to water the alkali. On the pigment that is permeated with water, if the red color of the wine turns blue-green, it proves that this is a good wine.