Creating a Chypre Note

Exercise taken from The Method of Jean Carles- Part 1, courtesy of Perfumer's Apprentice.

The following exercise has been significantly modified in order to fit the scope of both the materials I have available (the notes, their concentrations, etc.) and time constraints.  The classical chypre note is composed of the raw material of oakmoss absolute (which has been unfortunately heavily regulated by the IFRA, threatening the future of this genre of perfume), a base note known for a musty, mossy and earthy character, that, in my opinion, smells of molasses in high concentrations.

My first step was to create a small series of accords based on oak moss absolute and ambroxan (a synthetic alternative to ambergris), combined in varying ratios.  The first combination, 3 parts oakmoss and 1 part ambroxan, maintained the character of the oakmoss to a great extent.  While remaining remarkably similar to concentrated oakmoss absolute (complete with the molasses aspect, but also making room for a dark mossiness to peep out), it also smells slightly smoother and a bit less dark.  The roughness of the oakmoss raw material has been diminished noticeably.
The second combination, in which equal volumes of oakmoss and ambroxan have been combined, has even more evidence of the creaminess of ambroxan.  I find it interesting how the addition of this material doesn't as much disrupt the character of the oak moss so much as create the space for other aspects of the oakmoss to appear that are not nearly so noticeable when the product is highly concentrated.  In this case, I'm thinking of the mossy and musty facets that oakmoss is so famed for, which are now more prominent than the thick syrup/molasses qualities of the concentrated material.
The final combination is 3 parts ambroxan and 1 part oakmoss, creating an accord based principally on ambroxan (rather than on oakmoss, as the first was).  In this composition, it is the salty creaminess of the ambroxan that strikes me first, but after a slight space the oakmoss surfaces as a musty moss-like scent with just a bit of earthy deep sweetness.

In order to flesh out the scent further, and because the majority of chypres have a musky character, the next combination is composed of 3 parts oak moss, 4 parts ambroxan, and 1 part musk ketone (I have increased the ratio of ambroxan to oakmoss due to the relative concentratiosn of my materials- the oakmoss absolute to which I have access is of a very high concentration).  Building on the foundation of oakmoss absolute, which smells here primarily warm and mossy, earthy, with just a bit of sweetness, we have the musk ketone, which lends air to the composition and gives more play to the salty creaminess of the ambroxan while adding its own smooth, warm and lived-in, not quite clean and not quite dirty character.  It's a warm and drying forest floor in the afternoon with clean but slightly close air, and the whisper of a salty breeze every now and again, from an ocean just a little in the distance.

To this base, I added 2 parts of rose and 1 of civet.  The result is a fresh rose scent, soft pink petals spread across a darker and deeper base.  The base picks up the darker nuances of the rose.  There's a warm moss behind and beneath the flower, smooth and creamy and cushioned, with just a touch of dirty and salty animalic character  A warm rose, fresh and blush pink over a golden green background, a background with the smell of sun-heated mossy forest floor, and just a touch of warm fur and skin.  To my surprise, it's starting to actually smell more fleshed out.  Still too simple to be something that could actually be considered a perfume (and wouldn't it be just about the least original perfume one could imagine? (although I haven't added oud, so that's one point to its favor...)), but it smells more like the skeleton of a perfume than a simple accord.

To these heart and base notes Jean Carles recommends that one add top notes, specifically bergamot and sweet orange.  For this purpose I utilized bergamot (2) and mandarin aldehyde (1).  The sweet aldehydes and spicy citrus of bergamot are all that is noticeable at the outset, and the bergamot soon surpasses the sweet aldehydes in strength.  Citrus scents generally fail to interest me, so I will apologize and recommend that you take my only cursory appreciation of this last combination with a grain of salt. I do register, interestingly, that the bergamot smells spicy enough to have a passing resemblance to pepper.  Odd.  I will update this once the top notes fade somewhat more.  Update: The scent remains more peppery than the others, but draws closer to them with time.  I prefer the version one before this one, that was lacking the top notes.  Though it was rough initially, I find that the remaining bitter bergamot peel and pepperiness disturbs my appreciation of the heart and base notes.  I would prefer the citrus to be lighter, and would make that change were I to reformulate the scent.

Further work in Part 1 of Jean Carles' method recommends some experimentation with vetiver.  Now, vetiver is quite possibly my least favorite note.  Sorry to all of you vetiver fans out there, but, at least at this point in my exploration of perfume, smelling it gives me neither happiness nor pleasure.  So I may skip that bit.  Part 1 is wrapping to a close, it may have one post left in it, it may not.  Regardless, it's been interesting.

Photo of oakmoss stolen from Fragrantica.

Classification According to Volatility

Perfume notes are classified as being top, heart, or base notes, depending on the volatility of the molecules that comprise the note or accord.  Generally, lighter molecules, those with a smaller molecular weight, diffuse the most quickly; these are a fragrance's top notes.  The heart notes are composed of molecules with an intermediate molecular weight, which gives them some staying power, but not to the extent of the heavier base notes.

In Jean Carles' classification of perfume notes according to volatility, he refers to heart notes as 'modifiers of base notes'.  Using paper scent strips and a few fragrant materials, I measured the longevity of a few of the notes he mentions by the amount of time their characteristic scent lingered on the test strip.

Note:	Jean Carles' Classification:	Concentration:	Tenacity on Scent Strip:
Bergamot Italy	Top	1%	30 mins
Linalool	Top	5%	2 hrs 20 mins
Galbanum Turkey	Heart	1%	6 hrs 30 mins
Aldehyde C-12	Heart	9%	8 hrs 20 mins
Rose Absolute	Heart	1%	18 hrs 30 mins
Jasmine Absolute	Heart	1%	2 days 4 hrs
Vetiver India	Base	1%	3 days 4 hrs
Sandalwood Australian	Base	2%	7 days 7 hrs
Musk Ketone	Base	5%	9 days 4 hrs
Oakmoss Absolute	Base	50%	Forever

So my experimental evidence is more or less in agreement with the classifications provided by the perfumer's table.  I do wonder to what extent the concentration of the notes that I tested affected their longevity on the paper (which is greater than the longevity on skin), particularly in the case of the oakmoss, which is still going strong today, about 2.5 weeks after I dabbed the strip with absolute.  The power of the different notes varies not only from the standpoint of longevity, but also sillage/projection: the distance the scent emanates from the source.  Projection tends to increase with increasing concentration for each note, but galbanum diluted to 1% is still quite clearly stronger than the Aldehyde C-12 diluted to 9%.

What follows is a brief description of the ten notes discussed above.  Bergamot is a citrus note that also has a slightly bitter woody aspect.  Its use in perfumery is both very traditional and very common.  The perfume ingredient is obtained by pressing the peel of the bergamot fruit.  Citruses are a canonical top note, and bergamot is no exception.

Linalool is a natural molecule found in many plants and flowers, but can also be synthesized.  It is, like bergamot, very common, and has a light, clean floral scent, with a bit of green sweetness.  It smells smooth.  The molecular formula is C10H18O and the molecular weight is slightly over 150 g/mol.
Galbanum is an aromatic resin, a product of certain Persian plant species.  Its scent is greengreengreen, a bit too bitter, cold, harsh, or something to be fresh, particularly in high concentrations.  That said, I don't mean any of that in a negative way.

Aldehyde C-12 is, like most aldehydes, used to give a perfume more height or lift.  To me, aldehydes smell bubbly -almost carbonated- and buoyant.  Chemsitry-wise, aldehydes are molecules that contain a terminal carbonyl group, or a carbon atom double-bonded to an oxygen atom at the end of a chain.  Like linalool, aldehydes are natural molecules that have been reproduced in a laboratory setting.  Fatty, or aliphatic, aldehydes, the type that are generally used in perfumery, also contain a long chain of carbon atoms (generally 8-13) connected to the terminal carbonyl group.  Some other aldehydes used in perfumery contain a ring-like structure of carbons, such as benzaldehyde (which smells like almonds) and contains what is called, in organic chemistry, a benzene ring.  Aldehyde C-12's molecular formula is C12H24O, and it's molecular weight is a bit over 180 g/mol.  Aldehyde C-12 has powdery ambery citrus nuances.
Rose Absolute... despite the fact that extracts of flowers don't smell quite like the flower itself, as one would experience it in real life, I will say that the absolute in my possession is very recognizably rose.  And that said, there are many varieties of roses, each smelling somewhat differently.  Some are spicy and dark, others pinker and fresher and lemon-y.  Rose absolute is usually steam- or solvent-extracted from the flower (typical varieties being damascene and centifolia.
Jasmine, being a white flower, has an interesting scent.  Petal-like and creamy, with undertones of indole (a sort of dirty smell that is also present in feces and decaying garbage).  The absolute I used for this study comes from  the jasmine grandiflorum varietal, but jasmine sambac is also widely used in perfumery.  Jasmine absolute is extracted through a process called enfleurage, but there are synthetic jasmine-smelling substitutes available.
Vetiver is a type of grass native to India.  It smells woody, smoky, green-grey- somewhere between fresh and musty.
Sandalwood is a traditional perfumery material that has a creamy, milky, and rich warm wood fragrance.  The highest quality source of natural sandalwood is Mysore sandalwood in India, which is now protected from harvesting due to its being an endangered species.  What is commonly used in perfumery now is Australian sandalwood, which smells similar, though rather harsher.  Synthetic sandalwood molecules have also been developed.

Musk ketone is a nitro musk, created synthetically in the late 1800s and found to resemble Musk Tonquin 9 (a natural, highly pricy, and not quite cruelty-free material).  Most nitro musks have been eliminated for health and environmental reasons (for more about the health effects of nitro musks...).  It's formula is C14H18N2O5 and its molecular weight is about 290 g/mol.  I'm going to assume that musk ketone isn't carcinogenic. given that it was fairly easy to get access to.
Oakmoss smells... well, mossy.  In high concentration I find that it resembles molasses, while in lower concentration it smells rich, creamy, and earthy.  A component of fragrances in the chypre genre (do read this article about the history of the chypre), it has been heavily restricted due to dermal sensitization issues.  It is a species of lichen that grows usually on the trunks of oak trees in deciduous forests of the northern hemisphere, though it may also grow on other species of tree (in which case its odor is slightly different).  The absolute can be obtained by solvent extraction or vacuum distillation.

Having written about each note under inspection more individually, there are a few last things I found should be mentioned.  The first is that not all of the notes have a provided molecular weight.  This is because natural materials, like absolutes and essential oils, contain many different molecules, as opposed to synthetics, which are single molecules created in a lab through a synthesis reaction designed to yield that individual molecule.  For this reason, natural ingredients are often perceived as being more complex- after all, they have a more varied ingredient list.
However, for the molecular weights that were easily obtainable, we can see clearly that they increase with the experimental longevity I found- which fits the general rule that the lightest notes are the most volatile, and the heaviest the least volatile.

• Linalool photo stolen: Wikipedia
• Aldehyde C-12 photo stolen: Givaudan
• Musk keton photo stolen: Wikipedia

Luca Turin's Ted Talks 1

            What follows is a dissection of the first three minutes of Luca Turin's Ted Talks video entitled 'The Science of Scent.'  These first three minutes cover the top and heart notes of the well-known Estee Lauder perfume Beyond Paradise, gas chromatography of said perfume as a method of uncovering a rough estimate of the number of molecules that comprise it, the elements that generally compose scented molecules, and the molecular structure and naming of cis-3-hexenol, which smells of cut grass.

            As most people (or fragrance fans, anyway) are aware, perfume notes are divided into a pyramid-like structure: top notes, heart notes, and base notes.  A fragrance's development over time is a function of these distinctions.  Top notes have the lightest molecular weight and thus evaporate from skin and diffuse through the air the most quickly (they have generally disappeared within 10-15 minutes after application).  Citrus is a canonical top note.  Heart notes are somewhat heavier molecules, and base notes have the greatest molecular weight.

            After being unable to get a direct answer from anyone in the fragrance industry about the number of molecules in Beyond Paradise, he analyzed a sample of it with a gas chromatograph to get a general answer for himself (about 400 molecules).  Synthetics are generally one molecule, whereas naturals are compositions taken directly from a source found in nature, and are thus melanges of many different molecules.  For this reason, it is very possible that no one Luca Turin asked had a very definite idea of how many molecules might be found in Beyond Paradise.

            Gas chromatography is a technique we utilized in my organic chemistry class last semester in which the relative quantities of the components of a solution (such as a perfume) are measured.  The sample is injected into the injection port, which is set at a temperature higher than the boiling points of the sample's components.  Thus, the sample is rapidly heated and the molecules that make it up are vaporized shortly after injection.  A carrier gas, called the mobile phase (an inert, or unreactive gas or liquid that the vaporized sample can travel with and through) flows through the injector and pushes the components of the sample into the gas chromatography column.  The components of the sample, or the molecules of which it is composed, are separated based on the boiling points of the molecules and their relative affinities for the stationary phase (an immobile wax within the column that the molecules travel through).  Molecules with a greater number of molecular interactions with and attractions to the stationary phase will be slowed down on their trip through the column, whereas molecules that have relatively few interactions with the waxy stationary phase will be fairly unhindered.  Thus, the molecules become separated by how quickly they can pass through the column (which is dependent on their interactions with the stationary phase).  The components, after having traveled through the gas chromatography column, reach a detector which sends a signal to the chart recorder, resulting in a peak on the chart paper.  Each peak corresponds to a molecule found within the sample, and the area beneath each peak corresponds to the relative amount of that molecule present in the original sample.  Optimally, each type of molecule should reach the detector at a different time due to differences in attraction to the stationary phase.

            These molecules of which fragrances are composed are themselves comprised of building blocks called atoms.  Atoms have different identities depending on the umber of protons contained in their nuclei.  Each different number of protons (the atomic number) corresponds to a different element on the periodic table of elements.  The elements that generally combine to create fragrant molecules are carbon, hydrogen, oxygen, nitrogen, and sulfur.  These elements are found on the upper right of the periodic table, except for hydrogen, which is the upper and leftmost corner.  Molecules containing carbon are organic molecules, and are studied in organic chemistry.  This is the domain of chemistry that most molecules with scents fall under.

            Luca Turin uses the example of cis-3-hexenol, which smells of cut grass.  This compound contains a cis double bond and an alcohol (or -OH group).  There is a system for naming and numbering organic compounds.  Start with the longest chain of linked carbon atoms.  In this case, the carbon chain is six atoms long (thus, hexenol).  The -ol suffix alerts us to the presence of an alcohol group, while the fact that the molecule is hexenol as opposed to hexanol tells us that the molecule is an alkene (and contains a double bond) and not an alkane (and made entirely of single bonds between the atoms).  In this case, the alcohol is the 'highest priority substituent' and numbered first.  The molecule name takes the form cis-3- hexen-#-ol.  The # symbol denoting the position of the carbon at which the -OH group is attached.  Because the -OH group is attached at the end of the carbon chain, it is attached to carbon 1, and so it is not necessary to include the number.  counting from the carbon to which the alcohol group is linked (carbon 1) we eventually hit carbon 3, the first carbon of the double bond.  A double bond can be either cis or trans.  In a cis double bond, the most important substituents (with the greatest atomic numbers) are on the same side of the double bond.  In the trans form, the most important substituent on one carbon atom goes in the direction opposite that of the most important substituent on the other carbon atom of the double bond.  From this information, one can draw the molecule from the name, or name the molecule when presented with a drawing of it.

• Pyramid image stolen from Wikipedia.
• Gas chromatography diagram stolen from kutztown.edu
• Cis-3-hexenol image stolen from Wikipedia.