Part 3: Introducing the ABC of Perfumery©

Updated: Apr 5, 2018


Click acá para la versión en Español

This is the 3rd part of a series aimed to:

  1. understand the ABC of Perfumery© system created by Steve Dowthwaite, owner of;

  2. see how it can help us organize and catalog our materials and,

  3. create and analyze perfumes.

If you didn't read the first two parts I strongly recommend you to do so. This is a link to PART 1 and this is a link to PART 2. If you want everything to make sense, PLEASE start reading from the beginning. So far we have learnt what's the name of each category of smell and which letter represents, we also explained the concepts of Odor Profile, Relative Impact and how interrelated these concepts are with the headspace and the creation of accords. Let’s dig deeper into this incredible system:

Odor Life:

Let's go back to the odor impact table we were working with last post:

Probably, as soon as you started working with the concept of relative impact, you realized that it changes its value over time, rendering materials weaker and weaker. So ANOTHER quantifying value is necessary to measure how long a materials odor lasts. We measure this in a smelling strip up to the point that the odor becomes weak and uncharacteristic of itself. Even though this measurement will vary depending in a plethora of conditions like humidity, ambient temperature, air-flow, amount used on the sample, etc.; still we can get effective comparative values between the different materials (assuming also that the conditions are the same, even though not the ideal).

So, dip the tip of a blotter in the product to evaluate and measure how long it last. Use fractions: 1 hour and 30 minutes will be 1.5 (this will make future math calculations easier —and yes, unfortunately there’s a tiny bit of math—). Smell the blotter as often as you can to evaluate whether the smell of the product is still the same or have became weak and uncharacteristic of itself. Is this a boring process? Yes, it is. But luckily you have to do it only once. Is it important? Yes. It will let you evaluate the "dynamics" of your perfume as it evolves over time and understand the interaction with the other materials..

Now I'm going to assume you went ahead and smell and timed the 5 materials of the last table. And probably you ended up with something like this:

Remember that we type time in fractions, so, 4 is 4 hours, 0.5 is half an hour, 0.1 is 6 minutes, etc. In the case of sandalwood, You can trust the value or sniff everyday a blotter for more than 6 months to realize that it is still there...

Now, let's create a graph where we have relative odor impact on the vertical axis and odor time on the horizontal axis. We then insert the different materials in there to see whats going on:.

First we put the Iso Amyl acetate, which has an impact of 1200, but after only 6 cannot smell it anymore. So at 0.1 the odor of Iso Amyl acetate became weak or uncharacteristic of itself. Let's add all the rest:

By looking at the graphical representation of how different notes evolve on a mix, we can also deduct that even though from the marketing point of view the concept of the famous triangle with top, middle and base notes is useful and easy to explain, it is NOT that accurate: Is sandalwood a TOP note? With the triangle, of course, you would say no, but...Of course it is!, in the sense that IT IS interacting, as you can see at the beginning of our graph, with all the other materials! The smell at the opening of the perfume would be somehow different if the sandalwood wouldn't be there. So that means that sandalwood NOT ONLY plays a role as a base note, towards the end of the odor life of the perfume but at the beginning and the middle life as well!

Now, with relative impact we measured how "hard" the headspace hit our nose, then we measured how long a smell last but we still need some kind of measurement that tells us, as an average, taking into account both impact and life, how "strong" a smell is.

Well, let's go back to a graph, this time only adding the linalool, as an example:

The painted area represents what we are trying to achieve: how "strong" a smell is. We will call this variable odor strength, but how do we calculate it?

Easy peacy...basic geometry.!.

Since it is a triangle, we can calculate the area of the rectangle formed with the dotted lines and divide it by 2. As you can see, One side of the rectangle is our measurement of the odor life, the other side is the measurement of the odor impact. so we multiply those values (that gives us the area of the rectangle) and we divide it by two (we get half of it, the triangle).

What do we get?

We get the strength of that material and we measure it in odor units:

Linalool: 100 (impact) x 4 (odor life) / 2 = 200 odor units.

Now, let's put everything in a table:

Enough math. Why don't we jump for now into a more attitudinal, behavioral and psicological setting?

Training our sense of smell: Getting Synesthesia back

Before you dive into your next smelling session, let's review first some basics about the process of train our sense of smell:

  • The worst place to smell: Our lab. PLEASE, get out of there, go outside, where the sun shines and the air graze your face. You need your nose and your mind to be relaxed, encumbered and clear.

  • Use of blotters:

o Try to use always the same kind of paper (Thinner strips are better for

analytical smelling, thicker ones for presentation of samples.

o Dipping the strip 0.5 cm (0.2 inches) along the strip is more than enough. Let

the product spread until it is not wet. And THEN smell.

o For sniffing, hold it around ½ inch from your nose.

o Bend the tip of the blotter at about 2 inches. This will help you avoiding

touching your nose when you are smelling and, let's be honest, you will look

cool and more professional, like you know what you are doing. LOL, Just

kidding -or not-.

  • Be sure to be relaxed and not wearing any fragrance. Do not drink coffee or strong drinks right before or while smelling. Sitting down is probably better than standing, but experiment both ways and determine how do you feel and which way is better for you.

  • Method: Sniff and evaluate. Sniff for a really short period of time and try to think about the smell, mentally evaluate it and memorize it. Do not keep inhaling like a maniac. Your lungs are useless for this. All your smell receptors are inside your nose, really close to where your sample is and NOT on your lungs. Doesn't matter how much you try, the smell WON'T get there...The shorter and smoother the sniff, the better. Use your mind, analyze the smell. Record it. You will be surprised how well our mind can be trained to learn new things. Even if you think you will not be capable or that you are not intelligent...your mind learns regardless...LOL, just kidding.

  • Make notes. As many as you can.

  • Rinse and repeat

As we learn new concepts and measurements, we need to learn new ways of smelling as well. At first, the final goal is to smell with our brain and not with our nose. Once we are comfortable with this, we should add to the smelling process a new dimension: a sensual and emotional dimension, the part that we can actually end up "feeling the smell." This is related with the concept of synesthesia: this theory states that as newborns, our senses were mostly interconnected, interlinked and as we grew into adulthood we learnt how to compartmentalize and “un-link” them.

By asking questions like “if the smell is a color, what color would be” and expanding then this question further into the realm of sounds, shapes, textures, feelings or any other impression that might have been received during the smelling process, we are trying to reactivate those links and we are adding a layer that increases and fortifies the whole smelling experience.

The following are some responses, perceptions, associations and reactions given by people when they were asked about the different categories from the ABC. Nothing is absolute and you can think or feel something totally different. These are just average responses. Whatever your association is, it will help you improve your smelling process by adding an extra layer or dimension that would render the experience deeper.


Going back to classifying with the ABC, once we detect the main group or letter of a material, we can try to go a little bit further by trying to identify a secondary smell. Probably we have done so already when we made the odor profile and we identified different facets of the smell. Usually we would refer to this secondary smell as its “background smell”. As instance, Sage is a (H)erbal note that has a minty, cool or ice(b)erg background hence its classification would be Hb. This provide us with 676 possible theoretical classifications [26 (A-Z) * 26 (a-z)].

But don’t worry, with the exception of (F)ruity smells, usually only around 4 or 5 sub-classes are necessary.

Let’s see how we can use the sub-classifiers to further the categorization of different materials. The following sub classifiers are based primarily on the secondary odor note:

By now probably you are thinking “Hmm this seems to be quite smart” Maybe it is a good time to start arranging YOUR materials by the ABC? Can you imagine the benefits? It is obviously better than to arrange your materials just alphabetically! Can you see its practicality? It is also extremely useful for “replacements”: you need a material that falls into Fd but you don’t have it, well, look for another Fd in your organ and most likely you will have found almost the perfect replacement! This is impossible to achieve when your organization is alphabetically and you have the the Peach bottle standing by the Phenylacetic acid bottle and then the peppermint by its side!

As you can see, this is a learning process and what today you might think is a soft Ro, might be interpreted in the future, as you better your smelling skills, as a Ml. Eventually you will have the self-confidence to know that each material is being classified accurately. In the meantime, you might be redefining which group some materials belong to and changing labels accordingly. Not a biggie. It is always good to realize that we keep growing and learning.

Olfactory analysis:

You just smelled a perfume you know NOTHING about. The only thing you know is that you LOVE it and you would like to make your own version of it or somehow recreate it for your own pleasure, but…where to start? What are their main components? Your description probably would be something like “some kind of rosy smell, a little bit spicy, some peach and maybe some earthy base notes” but probably you have no idea how to even get close to a formula for that wonderful smell!

Do not despair, the ABC comes to the rescue again: By going systematically through the 26 ABC classifications, you will be able to determine the main aspects of the perfume you are trying to figure out. Smell analytically. First ask yourself if there’s any A in it, if yes, you assign a proportionate value and if no then you move in to B, where you ask again. You rinse and repeat with all the letters until the Z.

Often is as helpful to ask “what the fragrance is not” as it is to ask “what it is”. Once you are done, you will get what we will call the odor print of the perfume. This process may go something like this for a "Fragrance X"; (a L'air du temps' style fragrance). (From “Training the ABC's of Perfumery” by Stephen V. Dowthwaite, PerfumersWorld. Paper published in modified form in Perfumer & Flavorist, Allured Publications, USA 1999).

A word regarding the estimate of proportion in smell (head space): because not all the smells have the same odor impact, the percentages of what we actually smell (headspace) are not the same as the ones in a formula. We will take this into account, when we want to make modifications to the formula with some math. I KNOW! Everything was coming along SO good so far WITHOUT math, right? (Just a reminder of what is coming…lol)

Now, we’ll make a second pass to identify which sub-classification applies for each category to help us with the description of the perfume:

Finally, combining the data from the odor print and the sub classifications, we could arrive to the following description:

“Fragrance X"

A heart (main) of Rose de Mai, Carnation, Light Floral Muguet with notes of Spice, Orchid. A top note of Bergamot and nuances(<1%) of Flowery Green and Peach notes Blended with Bois de Rose, Musk, Iris, Ylang, Fixed with Benzoin, Vanilla, Ambergris, Civet and Moss.

Well, Only one more part to go to fully understand and expose the potential of this incredible system!

Remember that The Art and Technology of Perfumery Foundation + Course will be held April 23-27 at the Perfumer's Studio in LA, California for the very first time translated to Spanish. Let this be known to anybody that might be interested!

If you enjoyed, or did not, have questions or corrections or just want to vent or ramble, please, leave a comment.

Hope you all have a wonderful week!




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