Sizes of rods for permanent wave hairstyles are three-sixteenths inch, one-fourth inch, five-sixteenths inch, three-eighths inch and seven-sixteenths inch. Perm rods are designed in standard colors for certain sizes. From smallest to largest for curly perm styles, rods are red, blue, pink, gray and white. Large body-wave rods are purple.
Even larger rods are sometimes seen in orange. Different rod manufacturers sometimes use shades of colors that vary slightly from rods of the same size made by other manufacturers. Rods are available in straight and concave versions. Concave rods flare at the ends and are slightly thinner in the middle. The shape allows rods to fit tightly against the scalp. Concave rods also vary the size of curls for a more natural appearance. Straight rods produce uniformly sized curls.
Permanent waves use chemicals to break and recreate bonds in hair. Perm rods are rolled in hair, and a base and wave lotion are applied. The mixture of the two chemicals creates a reaction that softens the hair and causes it to stretch and mold to the shape of the perm rods.
After curly perms, hair is usually blow-dried and cut to highlight the curls and to distribute hair weight evenly. For body waves, hair may be styled to emphasize volume rather than curls. After the permanent solution is applied, hair may be blown out with a hair dryer or set in different sizes of rollers.