The Practice of Modern Perfumery continues its discussion of the odor wheel. As we’ve seen, the lines between each of the points represent sultry, fresh, exalting, or soothing odor effects, while those points that are in opposition--anti-erogenic versus erogenic, and narcotic versus stimulating--create other odor effects. Anti-erogenic aromas suppress erogenic aromas and stimulating elements such as spices, burnt substances, and gourmand materials balance the tendency of the narcotic to intoxicate and put us to sleep when that’s not what we’re supposed to be doing at all. The opposition of the contrasting points introduces tension in the perfume and gives it power.

Mr. Jellenek discusses animal (erogenic) ingredients such as castoreum, civet, musk, and ambergris; and erogenic compounds of plant origin, namely costus root and ambrette seed. Last, there is the aroma chemical, indole. Indole forms part of the smell of certain flowers—jasmine, orange flowers, and acacia are a few. While indole is considered fecal, and has a distinctly dissonant aroma, these flowers wouldn’t be themselves without it. Other aroma chemicals with fecal nuances are phenylacetic acid and its esters (which also smell like honey), phenyl ethyl alcohol (which smells like roses, but has a gentle funky note), and the paracresols (which smell like creosote and tar; they get animal in a perfume).

Now it gets interesting. While these odors are, according to Jellinek, fecal, there are also so-called sweaty notes. These notes are represented primarily by aldehydes, specifically those having from eight to 12 carbon atoms. He goes on to declare that both sweaty and fecal notes must be included together, with the obvious conclusion that any complex containing indole or any other fecal-like aroma, must also contain an aldehyde. This combination occurs frequently in plants, with various proportions of the two elements coming into play.

Now I’m experimenting with using aldehydes in Black Iris. I tried some C-12 MNA, an often-used aldehyde, and found that it focused the perfume and somehow makes it more perfume-like, more sophisticated.

In another section, Dr. Jellinek describes 14 aroma chemicals. Some are less important than others—they are familiar compounds and have been much written about—but I did find a couple of interesting comments.

One entry is about l-citronellol. Citronellol is a classic ingredient in rose perfumes, but many perfumers don’t recognize the importance of l-citronellol versus d-citronellol. (These two are mirror images of each other; the first one rotates light to the left, the other, to the right.) Our doctor recommends using “cheap d-citronellol” to make soaps and for other utilitarian uses, but, l-citronellol, he considers “one of the most important components of natural rose perfumes.” For those who have worked with rhodinol, he insists that rhodinol isn’t a compound unto itself, but rather a combination of geraniol and l-citronellol.

Methyl anthranilate is a chemical that smells to me, exactly like Concord grapes, the kind used to make Welch’s grape juice. I sometimes use it in floral blends when I want a fruity note, but Jellinek mentions something new (to me). He insists that methyl anthranilate, along with alcohols (which end in –ol) and esters (which end in –ate, -ite, or ‘-ide), is narcotic. But this is the line that caught my eye: “…a high indole content is always accompanied by a high content of methyl anthranilate.” So, of course, I had to try it out on Black Iris, which contains indole. First, I added too much, not realizing how strong it was, and the perfume smelled tutti fruiti. When I backed off a bit, I noticed the methyl anthranilate brought out the floral aspects of the perfume and gave them a slightly orange blossom quality; it seemed to make them more diffusive. I’m not including it, though, because I want to bring out the rooty aspects of Black Iris rather than the floral ones.

It’s something to think about. In a day or two, I’m talking about An Introduction to Perfumery by Tony Curtis and David Williams. It’s one of my favorites.