Top / Middle / Base Notes & Formulations

TOP/MIDDLE/BASE NOTES

In olfactory training, learning to separate a complex scent into top, middle, and base notes is a lot like training your ears to pick out the treble, mid-range, and bass in a piece of music. It relies entirely on understanding volatility—how fast the individual aromatic molecules evaporate.

Because different compounds evaporate at different rates, a scent actually tells a story over time. Here is the practical guide on how to detect and isolate these notes during your training sessions.

1. The Evaporation Timeline

To isolate the notes, you have to use time as your primary filter. You cannot easily separate them the exact second you sniff a fresh bottle, because all the notes hit your nose at once. Instead, track the scent as it ages.

2. Step-by-Step Training Protocol

To practice this, use an olfactory scent strip (blotter) rather than smelling directly from a bottle, as the concentrated vapor in a bottle masks the subtle transitions.

Step 1: Catching the Top Notes (The First Impression)

• Action: Dip the tip of your scent strip into the oil or spray it once. Wait 5 seconds for any alcohol carrier to flash off, then take a short, gentle sniff.
• What to look for: Focus on the immediate, sharp impact. Top notes are often citrusy, herbaceous, or fiercely fresh. They hit the top of your nasal cavity quickly.
• Mental Prompt: What is the very first loud shout I hear? Is it bright, cold, or sharp?

Step 2: Finding the Middle Notes (The Heart)

• Action: Leave the strip alone for 20 to 30 minutes, then come back to it.
• What to look for: Notice what has vanished. The initial sharpness or "zing" of the top note will be gone. What remains is a richer, more solid aroma. This is the "heart" of the plant or fragrance—often floral, spicy, or green. It feels wider and softer in your nose than the top note.
• Mental Prompt: Now that the initial brightness has quieted down, what is the core personality left behind?

Step 3: Unearthing the Base Notes (The Anchor)

• Action: Check the strip again after 2 to 4 hours (and sometimes even the next morning).
• What to look for: By this time, the top and middle notes have completely evaporated. What is left are the heavy, sluggish molecules. Base notes feel "heavy" or "warm." They linger at the back of your throat or deep in your sinuses. These are your woods, resins, earth, and deep musks.
• Mental Prompt: What is the heavy, quiet residue that refuses to leave the paper?

3. Techniques to Sharpen Your Awareness

• The "Varying Distance" Trick: Top notes travel through the air faster than base notes. If you hold a scent strip about 6 inches away from your nose and wave it gently, you will catch a higher percentage of the volatile top notes. If you bring the strip right up to your nostril, you force your receptors to engage with the heavier, slower-moving middle and base molecules.
• Use Comparative Visualization: When sniffing, don't just think of the name of the plant. Think about texture, color, and weight. Top notes often feel like yellow, light green, bright, or misty. Middle notes feel like velvet, deep green, or smooth. Base notes feel like brown, dark red, sticky, thick, or warm.
• Keep a Multi-Stage Journal: Write down your impressions at three distinct times: 0 minutes, 30 minutes, and 3 hours. Documenting how a single oil (like Rose or Bergamot) changes over those intervals is the fastest way to rewire your brain's olfactory processing.

BLOTTING PAPER

1. High-Quality Fine Art Papers (Best for Cutting Your Own Scent Strips)

Professional olfactory blotters are made from heavy, textured, unsized (highly absorbent), and completely fragrance-free paper. Premium heavy-weight cotton art papers make an excellent substitute—you can simply cut them into thin strips. High-quality, professional art papers (like Rising Stonehenge art paper pads and premium watercolor/printmaking sheets) are perfect for absorbing and holding essential oils or botanical extracts over hours of testing.

2. Cosmetic Blotting Papers (Best for Quick, On-the-Go Testing)

If you want something pre-cut and incredibly thin, cosmetic oil-absorbing sheets work in a pinch for short-term testing (though they won't hold a scent for 24 hours as well as thick cotton art paper). Crucial Tip: Make sure to buy the unscented, un-powdered variety so it doesn't interfere with your training.

Target carries Skin Gym unscented blotting papers and their Up & Up brand oil-absorbing sheets in the beauty aisle. Walmart carries Equate or Clean & Clear oil-absorbing sheets in the cosmetics section.

A quick tip for your training: If you end up buying a sheet of premium cotton paper , cut the strips with clean, fragrance-free scissors, and handle the paper by the very tips to avoid transferring any oils from your fingers to the area where you’ll be placing your botanical scents!

CONSTRUCTING A BALANCED BLEND

Creating a balanced botanical blend is an exercise in both chemistry and sensory art. The goal is to build a "scent pyramid" where the different rates of evaporation (volatility) create a smooth, evolving experience rather than a chaotic flash of scent that disappears into muddiness.

Here is a step-by-step clinical protocol for constructing a botanical blend from scratch, using a balanced ratio of top, middle, and base notes.

The Master Ratio: 30-50-20

While there are no rigid laws in formulation, a time-tested baseline for a balanced, full-bodied aromatic profile is the 30-50-20 rule:

• 30% Top Notes: The first impression. Sharp, bright, and fast to evaporate (lasts 1–2 hours).
• 50% Middle (Heart) Notes: The core personality. Rounded, complex, and body-giving (lasts 2–4 hours).
• 20% Base Notes: The anchor. Deep, heavy, and slow to evaporate; acts as a natural fixative (lasts 4–24+ hours).

Blending Protocol

1. Define Your Formulation Goal

Prerequisite

Decide on the intent of the blend. Are you looking for an uplifting, clearing profile (heavy on citrus/camphorous), or a deeply grounding, calming profile (heavy on woody/resinous)? This dictates which aromatic families you select from the wheel. (See Aroma Wheel)

2. Select One Oil per Level

Cross-Family Selection

To ensure depth and prevent a flat profile, select oils from distinct but harmonious families on the aroma wheel: Top Note (Citrus/Camphorous): Bergamot (Citrus family) – bright, slightly floral, and universally appealing. Middle Note (Floral/Herbaceous): Clary Sage (Herbaceous family) – herbaceous, sweet, with tea-like undertones. Base Note (Woody/Resinous): Cedarwood (Woody family) – warm, balsamic, grounding, and anchoring.

3. Calculate the Drop Count

10-Drop Trial Batch

Always work in small, scalable trial batches before scaling up to larger volumes. Using a 10-drop total baseline makes the math simple: Top Note: 3 drops (30%) Middle Note: 5 drops (50%) Base Note: 2 drops (20%)

4. Build from the Bottom Up

Compounding

In a clean, amber glass vial, add your base notes first (2 drops of Cedarwood). Base molecules are large and heavy; adding them first allows them to sit at the bottom of the vial and begin acting as a fixative for the lighter molecules to come.

5. Layer the Heart and Top Notes

Integration

Add your middle notes next (5 drops of Clary Sage) directly into the base. Swirl gently. Finally, add your top notes (3 drops of Bergamot). Cap the vial tightly.

6. The Synergy Phase (Synergizing)

24 to 48 Hours

Do not judge the blend immediately. Leave the capped vial in a dark, cool place for a minimum of 24 to 48 hours. During this time, the distinct volatile components undergo chemical interactions (esterification and molecular bridging), smoothing out sharp edges into a cohesive "synergy."

Evaluating and Adjusting

Once the synergy phase is complete, evaluate the blend using a clean paper scent strip rather than sniffing directly from the bottle.

The Evaluation Drill: Dip the tip of a strip into the vial. Sniff immediately for the Top Note impression. Wait 15 minutes to evaluate the Heart, and check the strip again in 2 hours to see how the Base holds the remaining aromatic structure.

• If it feels too harsh or medicinal: Lift the heart by adding 1 drop of a soft middle note (like Lavender or Sweet Marjoram).
• If it disappears too quickly: The base is too weak. Increase the base note by 1 drop or introduce a heavy resinous fixative like Frankincense or Patchouli.

Measurement

Converting from drop counts to precise weight percentages is the critical leap between hobby blending and professional manufacturing. Drops are notoriously inaccurate because they are heavily influenced by viscosity (a thick oil like vetiver vs. a thin oil like lemon) and temperature, as well as the specific orifice reducer or pipette used.

To scale up accurately, you must shift your mindset completely from volume (drops) to mass (grams).

The Concept: Specific Gravity & Mass

Every essential oil has a unique Specific Gravity (SG), which is its density relative to water.

• Water has an SG of 1.00 (1 mL} = 1 gram.
• Most essential oils are lighter than water, typically ranging from 0.850 to 0.970.
• A few heavy oils (like Wintergreen or Clove) are denser than water, with an SG above 1.00.

Because of this, 1 mL} of Lemon essential oil weighs less than 1 mL} of Vetiver essential oil.

The 3-Step Conversion Protocol

To convert your 10-drop bench trial recipe into a precise formula for a 100-gram production batch, follow this protocol using a digital scale accurate to 0.01 grams.

Step 1: Establish Your Benchmark Weight (The Baseline)

Before you can use percentages, you need to know exactly how much your specific "drops" actually weigh using your specific equipment.

1. Place a small beaker on your scale and tare (zero) it.
2. Count exactly 20 drops of your chosen essential oil into the beaker.
3. Record the total weight in grams.
4. Divide that number by 20 to find the average weight of a single drop for that specific oil.

Example Calculation: If 20 drops of Cedarwood weigh 0.60 grams:

0.60 g = {20 drops} = 0.03 g per drop

Step 2: Calculate Total Grams for the Trial Blend

Repeat Step 1 for every oil in your trial blend to find their individual drop weights. Then, multiply by the number of drops used in your original recipe to find the total mass of the trial.

Let's convert a hypothetical 10-drop trial batch using this method:

Step 3: Convert to Weight Percentages (W/W%)

Now that you have the mass of each component and the total mass of the blend (0.275 g), calculate the true weight percentage (W/W%) using the formula:

Weight % = Mass of Individual Oil , Total Mass of Blend} times 100

• Bergamot:  (0.075}{0.275} times 100 = 27.27%
• Clary Sage: (0.140}{0.275} times 100 = 50.91%
• Cedarwood: (0.060}{0.275} times 100 = 21.82%

(Note: Your final percentages should always sum to exactly 100%.)

Scaling to Any Batch Size

Once you have your master formula in weight percentages, scaling up to manufacturing size is incredibly simple. You multiply the target batch weight by the percentage of each oil.

If you want to create a 500-gram batch of this master concentrate:

• Bergamot: 500 g times 0.2727 = 136.35 g
• Clary Sage: 500 g times 0.5091 = 254.55 g
• Cedarwood: 500 g \times 0.2182 = 109.10 g

Manufacturing Best Practices

• Work in a Temperature-Controlled Room: Volatile top notes will evaporate rapidly into the air during compounding if the room is too warm, changing your final batch percentages.
• Tare Individually: When manufacturing, place your bulk container on the scale, tare it to zero, weigh the first oil, tare it to zero again, and then weigh the second oil. This prevents compounding math errors in real time.

Base Notes and Fixatives

Citrus top notes (like Lemon, Lime, Bergamot, and Grapefruit) are primarily made of light, high-velocity monoterpenes like limonene. These molecules flash off the skin or out of a blend within an hour or two because they have low molecular weights and high vapor pressures.

To slow down this evaporation without drowning out the bright, uplifting quality of the citrus, you need natural fixatives. Fixatives work through physical and chemical mechanism—their large, heavy molecules physically anchor the smaller citrus molecules, lowering their overall vapor pressure and retarding their escape.

1. Resin and Balsam Fixatives (Chemical Anchors)

Resins and oleoresins consist of heavy, complex diterpenes and triterpenes. They act almost like an invisible, breathable mesh in a blend, offering exceptional chemical affinity for volatile oils.

Frankincense (Boswellia carterii / frereana)

• The Scent Profile: Terpenic, resinous, woody, with a natural, crisp balsamic lemon-top note.
• Why it works for Citrus: Because frankincense naturally possesses its own faint, high-clear citrusy undertones, it is one of the absolute best fixatives for citrus. It anchors the blend without muddying or darkening the bright opening impression of the citrus oils.

Benzoin (Styrax benzoin)

• The Scent Profile: Rich, sweet, balsamic, reminiscent of vanilla.
• Why it works for Citrus: Benzoin contains high amounts of benzoic and cinnamic acids, which are massive molecules. It creates a classic "gourmand" or warm effect when paired with citrus (think a creamy orange-vanilla or a rich lemon-mercurial sweetness). It slows evaporation drastically but will significantly sweeten the blend's heart.

2. Root and Wood Base Notes (Physical Anchors)

Heavy roots and heartwoods are rich in dense, dense sesquiterpenes and sesquiterpenols. These components are viscous and dry down incredibly slowly, holding onto lighter notes by simple physical entanglement.

Vetiver (Chrysopogon zizanioides)

• The Scent Profile: Deeply earthy, smoky, root-like, and thick.
• Why it works for Citrus: Vetiver is incredibly heavy and highly viscous. Just a tiny fraction of a percent in a formula acts as a massive anchor. When paired with bright top notes like Grapefruit or Bergamot, it yields a sophisticated, clean, "roots-and-rain" unisex profile.

Sandalwood (Santalum album / spicatum)

• The Scent Profile: Soft, buttery, precious wood, smooth, and highly tenacious.
• Why it works for Citrus: Sandalwood is a passive, non-aggressive fixative. Unlike patchouli or vetiver, it doesn't try to dominate the aromatic profile. It sits quietly at the base, absorbing the sharp impact of citrus top notes and smoothing out their chemical edges into a creamy, long-lasting dry down.

3. Seed-Derived Fixatives (The Molecular Bridge)

Ambrette Seed (Abelmoschus moschatus)

• The Scent Profile: Musk-like, nutty, slightly floral, and ambrette-rich.
• Why it works for Citrus: Ambrette is the plant kingdom's answer to traditional macrocyclic animal musks. Musks are premier fixatives because they act as a molecular bridge between mid-tier volatile compounds and the very heaviest bases. It adds an expensive, clean, skin-like longevity to light citrus colognes without altering the citrus scent profile itself.

Formulating for Maximum Longevity

When your goal is preserving a citrus top note, look at how you balance the base note types:

Formulation Tip: To keep a citrus blend alive even longer, leverage "bridge" notes in the middle layer. Adding middle notes that contain trace amounts of both top and base-like components (such as Ginger or Coriander Seed) creates a smooth chemical gradient that slows down the monoterpene escape even further.