In short
A balanced formula has something to smell at every stage, with no sudden drop in the middle. To find gaps, rate the fragrance's strength and character on a strip at set times and draw a rough chart. Then fix a dip by adding materials of intermediate volatility, related to the idea, rather than just adding more at either end.
What you will learn
- Map a formula's lines by rough volatility
- Find gaps in a fragrance's development using timed strips
- Close a gap with a chosen bridging material
Before this lesson: Design a Perfume's Drydown
Map your lines first
Take your formula and sort each line into a rough volatility band, using your own timing notes and the encyclopedia. You are not looking for precision. You want to see whether any band is nearly empty.
| Band | Perceptible for about | Examples |
|---|---|---|
| High | Minutes to an hour or so | Limonene, many citrus oils |
| Upper middle | A few hours | Linalool, benzyl acetate |
| Lower middle | Many hours | Phenylethyl alcohol, Hedione |
| Low | Days or longer | Musks, many woods, vanillin |
Chart the fragrance
Dip a strip, and rate the strength from 0 to 5 at 1, 5, 15 and 30 minutes, then 1, 2, 4, 8 and 24 hours. Also write one word for character. Plot strength against time. A smooth decline with a slowly changing character is usually what you want. A dip or sudden shift marks a place to work. Keep expectations modest: this curve records your perception on paper, and it will differ somewhat on skin and from one day to another.
Reading the chart
| Shape | Possible cause | First test |
|---|---|---|
| Falls off a cliff at 30 minutes | All top, little middle | Add upper-middle support |
| Dip at 1 to 2 hours, then recovery | Gap between heart and base | Add lower-middle bridge |
| Barely changes in the first hour | Heavy base masking the top | Reduce the base; check dose |
| Character jumps sharply | Unrelated stages | Add a link related to both |
Bridging, not stuffing
Choose a bridge related to the idea on one side or the other. For a citrus top over a woody base, a light floral or a soft woody-floral might carry the middle. Add it by ladder, then rerun the chart. If it works, the dip should be shallower, and the character should move more smoothly. If it merely adds a new smell, then you have the wrong material. Try another.
Sometimes a change is the point
Not every fragrance should be smooth. Some are built to change dramatically. Others hardly change at all, as the guide to linear and pyramidal fragrances explains. The test is whether the shape serves the brief. A gap you did not intend is a fault. A surprise you designed is a feature.
Practical exercise: Find and close one gap
- Sort your formula's lines into the four bands. Note the emptiest one.
- Chart the fragrance at the times above, and plot it on paper.
- Name one problem in the shape, and predict the cause.
- Add one bridging material, by ladder.
- Chart the new version next to the old, on strips prepared together.
You have done this well if you stated your prediction before testing, and your comparison shows what changed in shape, or honestly shows that nothing did.
Common mistakes
- Treating the chart as measurement. It is a single nose's rating, so only large differences mean much.
- Comparing strips of different ages. Always prepare them together.
- Filling every band because you can. A formula with a purpose may have an empty band on purpose.
Key terms
- Evaporation curve
- A chart of how strong a fragrance seems over time. It reflects perception as well as the physical evaporation of its materials.
- Bridge material
- A material of intermediate volatility added so that a fragrance has no perceptible gap as it develops.
Knowledge check
Written and reviewed by the RUŌOD Lab team. This is general education, not legal, regulatory, medical or safety advice. Example dilutions and exercises are for learning, are not validated products, and have not been safety-assessed. Completing a lesson confers no qualification. How we check these lessons.