What technique is used to smooth hair using a chemical substance?

The technique used to smooth hair with a chemical substance is straightening. This process typically involves applying a chemical solution to the hair, which alters its structure to make it smoother and more manageable. Chemical straighteners work by breaking down the bonds in the hair that create its natural curl or wave pattern. After the solution is applied, the hair is then usually heated with a flat iron to help lock the new, straighter shape in place.

This method allows for long-lasting results compared to other techniques, making it a popular choice for individuals seeking to straighten their hair more permanently or for an extended period. The effectiveness of this technique is especially noticeable on hair types that typically resist styling or hold wave patterns.