4.2 How Solvents Affect Diffusion & Scent Development

Introduction: The Role of Solvents in Perfumery

Solvents play a critical role in how a fragrance is perceived, how it develops over time, and how it diffuses into the air. They influence:
✔ Scent projection (how far the fragrance travels).
✔ Longevity (how long the fragrance lasts).
✔ Evaporation rate (how quickly the fragrance dissipates).
✔ Texture & skin feel (how the perfume applies to the skin).

Understanding how solvents affect diffusion and scent development is essential for both commercial perfumers and DIY fragrance creators.

1️⃣ What is Diffusion in Perfumery?

Diffusion refers to how a fragrance spreads into the air and reaches our nose. The solvent used in a perfume significantly affects the diffusion rate.

✔ Fast-diffusing solvents (like ethanol) create a strong initial scent projection.
✔ Slow-diffusing solvents (like DPG and MCT oil) make the scent last longer on the skin.

Example: Comparing Diffusion in Different Solvents

🔹 Ethanol-based perfumes → Fast diffusion, strong first impression, short longevity.
🔹 Oil-based perfumes (MCT, DPG) → Slow diffusion, subtle scent, long-lasting.
🔹 Isopropyl Myristate (IPM) → Balanced diffusion, lightweight, moderate longevity.

2️⃣ How Solvents Influence Scent Development

A fragrance consists of three main stages:

🔹 1. Top Notes (First Impression)

• The lightest, most volatile molecules (e.g., citrus, aldehydes, herbal notes).
• These notes evaporate quickly and define the perfume’s opening burst.
• A fast-evaporating solvent (like ethanol) makes the top notes stronger and more noticeable.

🔹 2. Heart (Middle) Notes (The Core of the Fragrance)

• Floral, fruity, and spicy notes (e.g., rose, jasmine, cinnamon).
• They appear after the top notes fade and define the main character of the perfume.
• A balanced solvent (like IPM) helps heart notes diffuse smoothly over time.

🔹 3. Base Notes (Longevity & Depth)

• The heaviest, slowest-evaporating molecules (e.g., musks, woods, resins).
• These notes last the longest and anchor the fragrance.
• A slow-evaporating solvent (like DPG or MCT oil) helps base notes stay on the skin for hours or even days.

3️⃣ Practical Example: Creating a Perfume in Different Solvents

Let’s create a simple floral-woody perfume and compare its diffusion in different solvents.

Ingredients for the Fragrance Blend:

✔ Top Notes: Bergamot (fresh), Orange (citrus)
✔ Heart Notes: Jasmine (floral), Rose (romantic)
✔ Base Notes: Sandalwood (woody), Musk (deep)

Testing in Different Solvents:

✔ Observation:

• The ethanol-based version had a strong citrus opening but faded quickly.
• The MCT oil-based version had a softer start but lasted much longer.
• DPG and IPM created a balanced, long-lasting diffusion.

4️⃣ Understanding Evaporation Rates & Their Effect on Diffusion

To visualize the diffusion process, imagine each solvent affecting evaporation like this:

Fast Evaporation (High Diffusion, Short Longevity)

🔹 Ethanol (Alcohol-based perfume)

• Fastest evaporation.
• Strong top note presence.
• Quick burst of scent but shorter longevity.

Medium Evaporation (Balanced Diffusion, Moderate Longevity)

🔹 IPM (Dry Oil Perfume)

• Moderately fast diffusion.
• Balanced transition between heart and base notes.
• Light texture, non-greasy feel.

Slow Evaporation (Slow Diffusion, Long Longevity)

🔹 DPG & MCT Oil (Oil-based perfume)

• Slower evaporation.
• Top notes fade gently, heart and base notes last longer.
• Creates a personal scent bubble rather than projecting far.

✔ Tip: If you want a stronger, long-lasting fragrance, mix fast and slow-diffusing solvents.

5️⃣ Practical Experiment: Comparing Evaporation Rates

Materials Needed:

✔ 3 Perfume Strips (Blotters)
✔ Ethanol-Based Perfume
✔ DPG-Based Perfume
✔ MCT Oil-Based Perfume

Steps:

1️⃣ Spray or apply the same fragrance in each solvent on separate blotters.
2️⃣ Wait 15 minutes, then smell each strip.
3️⃣ Observe after 1 hour, 4 hours, and 8 hours.

✔ Expected Results:

• Ethanol-based perfume will be strong initially but will fade quickly.
• DPG-based perfume will slowly release the scent over time.
• MCT oil-based perfume will have a soft but very long-lasting scent.

🎯 Conclusion: The choice of solvent affects how quickly a fragrance is perceived and how long it lasts on the skin or fabric.

Final Thoughts: Choosing the Right Solvent for Your Perfume

🎯 Next Step: Experiment with different solvents and fragrance compositions to find the perfect balance for your ideal perfume! 👃✨