Experts have devised a formula for what they believe is the perfect hair wash.

　　Tests were carried out over six-months on more than 500 volunteers to examine different methods of wetting, lathering and rinsing hair.

　　The result is a strict combination which differs depending on the length of the hair. The formula was devised by scientists at the research centre of beauty product brand Dove in Port Sunlight, Merseyside.

　　According to its scientists, only running water at a temperature of 36.7 C should be used. People with short hair should use no more than 6ml of shampoo, medium length 8ml, and long 10ml. Lathering should last 28 seconds and involve 20 rubs. Hair should then be rinsed for at least 22 seconds and repeated once to ensure cleanliness from the root to the tip.

　　The experts say conditioner is essential to complete the perfect wash. Again, the amount recommended depends on the length of hair - 2ml for short, 4ml for medium, and 6ml for long. The conditioner should be applied with a wide-toothed comb and left for 57 seconds before rinsing with water at 36.7 C. Finally, hair should be patted with a towel to absorb excess water, then left to dry naturally.