Volumize Volume Shampoo is a redensifying shampoo that creates long-lasting body and volume on fine, flat hair. Plenty of people complain of fine hair that appears flat, shapeless, and can't seem to hold a style for long. This happens because the diameter of the hair fiber varies from person to person; the smaller it is, the flatter the hair. A volumizing treatment can help this type of hair acquire greater body and structure, which translates into fuller locks with added bounce and movement.