Ivory Soap is one of the oldest and well-known brands of consumer goods giant, Procter & Gamble. It was first sold in 1879. Beyond that established fact…lies some controversy.

Ivory Soap: then…
This post grew out of a quick request from Athol, who had already written on P&G detergent products Tide and Dreft, to whip up something about the name, history, and slogans of Ivory Soap. Upon looking into things, we find that the sources vary.
1. Why it floats
The History Of Product Names section of the Trivia Library, The History of Soaps and Detergents page of About.com, and the History of Ivory Soap page of Essortment.com all cite the story that a workman accidentally left a mixing machine on during his lunch break, resulting in a higher air content in the unhardened soap mixture. The story then goes that the bars from that batch went out, and P&G found out about their new product only when they started getting letters praising “the soap that floats.”

James N. Gamble, the real father of “It Floats!”
Great tale, but Wikipedia says James N. Gamble, son of the founder, had figured out how to create floating soap, and made some notes on the process, which were discovered by P&G in 2004.
So, who’s right? Once again, Wikipedia’s process looks like the gold standard; their version is consistent with what is on the Ivory Soap web page.
[Actually make that the Ivory Soap Facebook page, which is where you now are re-directed. Looks like P&G senior management had some very garbled conversations with their grandkids, so let me straighten them out with some free advice: Facebook pages IN ADDITION TO, not INSTEAD OF, a product web site. Check it out, and you’ll see what I mean: anyone (not just a professional market researcher) would have a dreadful time trying to find information about Ivory Soap among the organic clutter that grows naturally in the Facebook environment. Yes, there are plenty of Facebook addicts out there, but that’s no reason to abandon the idea of a well-designed, informative web site that the grown-ups might want to visit.]
2. How it got its name
Once again, Trivia Library and Essortment.com are agreed on the story that that Harley Procter named the soap “Ivory” from a biblical verse he heard in a sermon (Psalm 45) “All thy garments smell of myrrh and aloes and cassia, out of the ivory palaces whereby they have made me glad.”
The other sources (Wikipedia, About.com, and, as best as I can tell, the Ivory Soap Facebook page) don’t dispute this account, but are silent on the subject. Given the century-plus life of the legend about the Sorcerer’s Apprentice mixing machine…who knows? (Maybe Harley Procter just had some naming skills, and figured out that the previous name—“White Soap”—was a bit too generic, and in need of something more memorable?)
3. Its slogans
Here, there is general agreement: in 1891, the slogan “It Floats!” was introduced. The other famous tag, “99 44/100% Pure”, which first appeared in an 1882 advertisement, came from an independent chemical analysis commissioned by Harley Procter.
4. Recent developments
The (IMO) best of the sources, Wikipedia, has information about the creation of new varieties of Ivory Soap, including some non-floating versions.

…and now.
Once again, a brief editorial opinion: if you change the single most identifiable attribute of your brand (rather than simply creating another brand of soap), then you’re coming up fast on the outside against Kraft-Mondelez in the “If it ain’t broke, don’t fix it” derby.
For an interesting, albeit critical, take on P&G’s brand innovation of late, have a look at this Business Week article; it may spawn some new posts here about what is (despite some of the criticisms in this post) one of the premier companies in the history of the U.S. –Greg Marus