A perm is a hairstyling technique wherein hair is rolled and then set using special chemicals. If all goes according to plan, the resulting curls with last for several months. If your hair is extremely straight or lifeless, getting a perm is a good way to produce natural-looking, semi-permanent curls without having to constantly toil with curling irons, hairsprays, and blow dryers. There are two general rolling techniques used for perms: traditional and spiral.
According to Happy Living Magazine, at HappyNews.com, a traditional perm is rolled using small concave or hollow rollers, which are typically made from plastic. Your hair is rolled in a horizontal orientation, so that the curls roll in underneath each other. Depending on the size of the rollers you use, a traditional perm can produce curls ranging from tight and compact to long and wavy (smaller rollers produce tighter curls, while larger rollers produce looser curls).
You can blow dry your hair after a traditional perm, which will effectively straighten your hair for a time. However, if you want to dry your hair while maintaining all of the perm's curls, the above source recommends that you use a blow dryer with a diffuser attachment. This attachment will broaden the airflow coming out of the blow dryer, protecting your curls.
Spiral perms are another semi-permanent curl holding technique. According to HappyNews.com, spiral perms started to gain popularity among women at the end of the 1980s, when having big, excessively voluminous hair was a fad. While spiral perms utilise the same types of curl-holding chemicals as traditional perms, the way in which the curls are rolled is completely different.
According to the above source, spiral perms are rolled using long, skinny rollers with grooved edges twisting around them--similar to construction bolts or screws. Your hair is twisted up and around the rollers in a corkscrew-like motion, and the rollers stand vertically atop your head while the curls set.
Like traditional perms, you can vary the tightness of the curls by varying the size of the rollers (skinnier rollers will produce tighter curls, fatter rollers will produce looser curls). According to HappyNews.com, to achieve optimal results when getting a spiral perm, your hair should be somewhat long. This will allow you to create layers of curls, making your hair look fuller.