Zest is a brand name, or trademark, which Procter & Gamble introduced in 1958 with the slogan "For the first time in your life, feel really clean." Early commercials stated that Zest is not a soap, because it does not leave the sticky film that soap does. A 1970-era commercial illustrated this concept with an apparent demonstration in which two photographs of a person were each dipped in one of two bowls, one labeled "soap" and the other "Zest" — the one that came out of the "soap" bowl had a scummy coating whereas the one that came out of the "Zest" bowl had no such coating. read more