Which of the following is a primary purpose of back brushing?

Back brushing is a technique primarily used to add volume and smoothness to hair. This method involves brushing the hair in a way that creates a cushion at the base, which lifts the strands and gives the hair a fuller appearance. When back brushing, the hair is lifted away from the scalp, and this movement helps to create a natural volume that can enhance various hairstyles.

Additionally, back brushing can help to smooth out the surface of the hair, contributing to a polished look, especially when styling with curls. While it may create some texture, its main function is not to create tight curls or enhance waves specifically, which are better achieved through other curling methods or tools. Similarly, back brushing does not serve the purpose of straightening hair, as this would require different techniques such as flat ironing or blow-drying with a round brush. Therefore, the primary purpose of back brushing aligns with adding volume and achieving a smooth finish in hairstyles.