Fragrance Pyramid: A Structure That Unfolds Over Time
A perfume is not a single moment; it is a sentence that unfolds over time. The fragrance pyramid is the grammar of that sentence. The top note offers the opening greeting, the middle note builds the body of the scene, and the base note is the signature that lingers. What separates these three layers is not a romantic hierarchy but an entirely physical reality: volatility — the speed at which a molecule disperses into the air.
Light, small molecules evaporate quickly and reach the nose first. Heavy, large molecules linger on the skin for hours. The pyramid is essentially a visualisation of this volatility curve. When the top note has dissipated, the middle layer takes over the stage; when the middle fades, the base note carries what remains.
An important point: the layers are not separated by sharp boundaries. A material can be "semi-volatile," bridging the top and middle. Think of the pyramid not as fixed boxes but as an overlapping gradient.
The Science of Volatility: Why Do Some Notes Evaporate First?
Three physical factors determine how quickly a molecule evaporates: vapour pressure (higher means faster evaporation), molecular weight (lower means lighter), and boiling point. Top notes are generally small molecules with high vapour pressure; base notes are large, heavy molecules with low vapour pressure.
This is why limonene (citrus) can evaporate within minutes, while Ambroxan (an amber structure) can remain on skin for days. Middle-note materials sit in between, acting as a bridge for roughly half a day. The table below provides a broad reference framework:
| Layer | Typical lifespan (indicative) | Volatility profile | Example raw materials |
|---|---|---|---|
| Top | First minutes – ~2 hours | High vapour pressure, light molecule | Bergamot, lemon, mint, pink pepper |
| Middle | ~2 – 8 hours | Moderate volatility, bridge | Rose, jasmine, lavender, geranium |
| Base | Hours – into the next day | Low vapour pressure, heavy molecule | Sandalwood, vetiver, amber, musk, balsam |
Weight-Percentage Distribution: The Classic Framework
Traditional perfumery offers a starting framework for roughly balancing the layers within a fragrance concentrate (i.e. the alcohol-free scent blend). This is not a fixed formula — it is a compass.
Commonly used starting ranges, as a percentage by weight of the fragrance concentrate:
| Layer | Classic range (by weight) | Effect |
|---|---|---|
| Top note | ~15–30% | First impression, opening brightness |
| Middle note | ~30–50% | Character, body, the heart's theme |
| Base note | ~20–40% | Longevity, depth, signature |
The cleanest way to manage these percentages is the 100-Parts Formula approach: count the total as 100 parts and distribute each layer across that 100. It scales easily and makes errors immediately visible.
Building an Accord in Practice: Step by Step
"Diluting a ready-made fragrance oil with alcohol" is not the only route. If you want to build your own accord — a harmonious blend of several raw materials — use the pyramid as a design tool. The sequence below is the safe path to building a balanced concentrate.
- Build the base note first
This is the skeleton that carries the whole structure. Identify your heavy molecules — sandalwood, amber, musk and similar materials. Adding the top before the base is settled is like building a house on sand.
- Settle the middle note
Add the floral or spicy heart that will bridge the base and the top. This layer gives the formula its character.
- Add the top note last
Introduce citrus or aromatic notes gradually for brightness and opening impact, increasing little by little as you smell. The top is the layer most likely to become overpowering.
- Weigh by grams; account for density
Write the formula in grams (g). Bear in mind that raw material specific gravities vary considerably: citrus oils run around 0.84 g/ml, while heavy resins and synthetics can exceed 1.10 g/ml. If you think only in grams but bottle by ml, you will end up with overflow or underfill; always apply the density factor when converting ml↔g.
- Dilute in alcohol; open with a small amount of water
Dissolve the concentrate in ethanol. If you wish to soften the initial sharpness of the alcohol and help the fragrance open up, you may add a very small amount of water. Note: water triggers clouding (louching) — it does not prevent it. As the water content rises, hydrophobic aroma molecules lose their solubility in alcohol and form micro-droplets, causing cloudiness. Start with minimal water and test for clarity; if needed, use a ready-made perfumer's alcohol.
- Maceration: room temperature, in the dark
Leave the sealed blend to rest in a dark location at room temperature (~15–20°C) for several weeks. Maceration is a process of chemical maturation; reactions slow as the temperature drops. For this reason, do NOT store in the refrigerator.
- Chilling and filtration: after maceration
Once maturation is complete, chill the blend separately at ~0–4°C for approximately 24 hours (chilling). This causes insoluble waxy compounds to precipitate. Then filter by cold filtration; otherwise sediment will settle at the bottom of the bottle.
When you want to boost the longevity of the base note, see Fixative Selection: Molecules That Anchor a Scent for guidance on choosing the right materials. Note: MPG (monopropylene glycol) and IPM (isopropyl myristate) are not true fixatives; they are carrier solvents/emollients that regulate volatility to a minor degree. True fixatives are macrocyclic musks, glucose ethers, and heavy balsams/resins. Using MPG above 2% can leave a tacky feel on the skin.
Common Mistakes, Balance and FAQs
Understanding the pyramid is straightforward; keeping it in balance is not. The most common mistake is making the top note dominant to create an impressive opening — only for the scent to empty out within half an hour. The second mistake is overdoing the base note, leaving the formula heavy and static. To strike the right balance between sillage (the trail a scent leaves) and longevity, refer to the Performance Optimisation: Sillage and Longevity Balance framework.
Should I keep the top/middle/base ratios the same in every formula?
If I increase the fragrance oil concentration, does longevity automatically increase?
Why should I weigh the concentrate in grams rather than relying on ml?
Build the pyramid, balance the layers, rest at room temperature, filter cold. The rest is your signature.
Related Articles
The 100-Parts Formula Approach
The advantages of building a formula in 'parts' rather than percentages, and how to scale it.
Read →Fixative Selection: Molecules That Anchor a Scent
Extending longevity with musk, amber, resin and synthetic fixatives.
Read →Performance Optimisation: Sillage and Longevity Balance
Adjusting the balance between a scent's projection and its longevity through formulation.
Read →