Hair washing

Hair washing is the cosmetic act of keeping hair clean by washing it with shampoo or other detergent products and water. Hair conditioner may also be used to improve hair's texture and manageability. Two-in-one shampoos, which have both detergent and conditioning components, are now commonly also used as a replacement for shampoo and conditioner.

To remove the sebum from the hair, some people apply a surfactant, most usually shampoo, but sometimes soap to their hair and lather the surfactant with water. The surfactant is rinsed out with water along with the freed dirt and dust it bonds to.

There are also dry shampoos, which are powders which remove sebum from the hair by soaking it up prior to being combed out.

Most hairdressers, in countries such as Canada, the U.S., and European and Latin American countries, offer a hair wash as a service before or after a hair cut. This is usually done to make hair more manageable for the hairdresser who will be performing the hair cut. After a hair cut, it can help remove any loose strands of hair that may be bothersome to the client. It is also quite a relaxing practice, and many clients enjoy a hair wash as their favourite part of a hair cut. Hairdressers use specialized basins to perform a hair wash, and these can be either forward or backward style.

In the backward version (which is more common), the client sits down in a chair, and leans their head back into a sink, with the hairdresser standing behind them.

In the forward version, the client leans forwards over a sink, and the hairdresser stands over them to wash their hair. In some parts of the world, such as China, it is not uncommon to see what is referred to as an 'upright' shampoo. In this style, the client simply sits in a chair as they normally would, while a hairdresser applies shampoo to their hair and adds water. They then rinse out in a basin.

...
Wikipedia