The molecule that is barely there until it is everywhere
Iso E Super was made on purpose, in a laboratory, by people looking for something else. In the early 1970s two chemists at International Flavors & Fragrances, John Hall and James Sanders, were working through the reactions of myrcene, a cheap terpene that comes out of turpentine and hops. One route led to a woody-ambery material they patented in 1973, and the patent that followed in 1975 is where the name first appears in print: a trade name, not a chemical one, for a mixture whose proper name runs to forty letters.
The molecule itself is unremarkable to look at, a small ring with a ketone hanging off it. What made it strange was how it smelled, or rather how it did not. Straight from the bottle many people smell very little. Put it on skin, wait, and a soft, dry, cedar-and-amber warmth appears that seems to come from the wearer rather than from the perfume. Then it vanishes again, then returns. That fading in and out is not imagination: the nose adapts to Iso E Super quickly, and the smell reappears as the adaptation wears off.
The odd part
For a long time the material was suspected of being two things at once. The commercial product is a mixture of isomers, and one minor component, often called the gamma isomer, carries most of the force. Later work at Givaudan on a related molecule made that explicit, and several houses now sell higher-purity versions under their own names. Most perfumers still reach for the ordinary grade, because the ordinary grade is what the last fifty years of formulas were written with.
Where it went
The first famous use is usually given as Halston for Men in 1975, very soon after the patent. The use that turned it into a legend came thirty years later: Terre d'Hermès, composed by Jean-Claude Ellena and released in 2006, is widely reported to carry it at a concentration that would have been unthinkable a generation earlier, and a few years later a perfume appeared that was, reportedly, nothing else at all. Whether that last claim is exact is disputed; that it could plausibly be true tells you everything about the material.
At the bench
Iso E Super is the rare ingredient that makes a formula better by making it less. It smooths rough edges, lengthens the drydown, and gives sandalwood, vetiver and cedar accords a quiet base to sit on. Dose it by hundredths and it disappears into the blend; dose it by tenths and the blend disappears into it. The substitutes listed on its catalog page exist because it has become so common that some perfumers now want the effect without the signature.
Open Iso E Super on your bench Its catalog page What replaces it
Sources: iff.com · US patent 3,929,677 (Hall and Sanders, International Flavors & Fragrances, 1975)