Which tool is used for chemical hair straightening?

A flat iron is primarily designed for smoothing and straightening hair. In the context of chemical hair straightening, it is often used in conjunction with chemical products to enhance the effectiveness of the treatment.

When performing a chemical hair straightening process, the hair is treated with chemicals that break down the bonds that cause the hair to curl or wave. After the application of these chemicals, a flat iron is often used to further straighten the hair, providing a sleek finish. The heat from the flat iron helps seal the hair cuticle after the chemical treatment, which can result in a smoother and shinier appearance.

The other tools listed serve different purposes. A curling iron is used to add curls or waves to hair, a hair dryer is primarily for drying and styling but not specifically for straightening, and a round brush is typically used during blow-drying to create volume and shape rather than straightening. Thus, a flat iron is the most appropriate tool for the specific purpose of chemical hair straightening.