Wikipedia
S-Curl is a trademark for a line of hair products produced by Luster Products designed to loosen the natural hair texture of a person of African descent, so that natural wave and curl patterns are looser and more prominent. The term "s-curl" soon came to describe the hairstyle acquired from the use of the S-Curl line products and the products of competitors.
Depending upon the strength of the application, an "s-curl" hairstyle can have hair texture only slightly less kinky than natural tightly coiled African hair. Similar to a woman's permanent, an s-curl is applied using relaxers containing lye, and, like a jheri curl, requires continued use of specialized shampoos and conditioners to keep the chemically altered hair from becoming dry, hard, and brittle.
S-curls were most popular among African-American men during the 1990s, when many popular musicians such as Timbaland and the members of Dru Hill wore the hairstyle. While no longer wildly popular, S-Curl products and competing products continue to be sold.