According to the principle of heat expansion and cold contraction, warm water will open all the pores first, and it will be clean at this time. Then wash with cold water to shrink pores and prevent dirt and bacteria from entering pores. As long as you insist, you must ensure that your face is clean and there are no blackheads.
Wash your face with warm water first, and use it with facial cleanser to deeply clean your skin, and then pat your face with cold water to calm your pores.
Extended data:
Effective face washing is also related to water quality and water temperature. Generally speaking, water quality refers to hard water and soft water. Hard water, such as well water and water containing calcium salt, light salt and minerals, is not easy to foam because it contains minerals, so don't wash your face directly with hard water. If the conditions are limited, you can boil the hard water for a few minutes to allow the minerals in the water to fully precipitate before using it. Soft water refers to water that does not contain or contains a small amount of calcium and magnesium salts, such as rainwater and tap water. Soft water is an ideal product for washing your face.
References:
Baidu encyclopedia washes face