Hair straightening

Hair straightening is a hair styling technique used since the 1890s involving the flattening and straightening of hair in order to give it a smooth, streamlined, and sleek appearance. It became very popular during the 1950s among black males and females of all races. It is accomplished using a hair iron or hot comb, chemical relaxers, Japanese hair straightening,Brazilian hair straightening, or roller set/blowdryer styling. In addition, some shampoos, conditioners, and hair gels can help to make hair temporarily straight.

The process is often called "rebonding" in some countries from Southeast Asia (e.g. Singapore, Malaysia and Philippines). The term "rebonding" was first used by REDS Hairdressing from Singapore in the late 1980s, which slowly spread to the rest of the region. If done often, flat irons and chemicals can be damaging to hair. Excessive straightening often results in split ends. However, heat protectant sprays can decrease the damage.

Hair irons and hot combs are designed to temporarily modify the shape/texture of hair. The straightened effect will usually be reversed by environmental factors, mainly contact with water from washing, rain, humidity, etc. This includes water in styling products such as gels applied after straightening, although careful use of such treatments can still produce usable results not much different from if the user had naturally straight hair before applying the product.

Overuse of heat tools can permanently alter the hair's structure. This is known as "heat damage". Use of protective sprays or lotions prior to heat styling may help to prevent heat damage. Once the damage has occurred, it can be disguised using various styling techniques, but not reversed. The only way to repair heat-damaged hair is to cut off the damaged hair and regrow it.

Five major tools can be used for hair straightening without any chemical treatment:

...
Wikipedia