Which tool is used to create curls when styling hair?

The curling iron is specifically designed for creating curls in hair, making it the primary tool for achieving this look. Its shape—usually a cylindrical barrel—allows stylists to wrap sections of hair around it, applying heat to create defined curls or waves. The adjustable temperature settings on many curling irons also enable users to customize the heat level according to the hair type, ensuring effective styling without causing undue damage.

Other tools listed do not serve the same purpose. For instance, a straightening brush is intended for smoothing and straightening hair rather than adding curls. A hair dryer is typically used to dry hair and can be paired with specific styling techniques (like "curling" with a diffuser attachment), but it doesn't inherently create curls on its own. Heat protectant is a product used to shield hair from heat damage during styling; it does not possess curl-forming properties. Therefore, the curling iron stands out as the essential tool for creating curls.