Hair smoothening is a chemical process that involves saturating the hair with a formaldehyde solution, which is then dried out and locked in a straight position using a flat iron. However, the chemicals used for hair smoothing are not as strong as the ones used in hair straightening treatments.
Hair Smoothening is usually subdivided into two popular treatments: Brazilian Blowout and Keratin Treatment. Both treatments bond protein to the external stratum of the hair. But brazilian keratin treatment has become popular because the procedure is compatible with bleached hair and gives the hair a naturally smooth, shiny look.
First, a formaldehyde solution is applied to the hair. The water in the solution breaks the hydrogene bonds of the keratin molecule. It is then blow-dried straight (a flat iron can also be used). The newly redesigned keratin remains straight because the formaldehyde crosslink the keratin filaments in perfect alignment. This makes the hair comparatively straighter and shiny.