Stability and cost
Discoloration, testing and formula cost
Fisfis Academy · 15 min read ·
What you will learn
- Explain why a perfume's color and scent change over time
- Understand the logic behind accelerated heat, light and freeze-thaw tests
- List the main formula and packaging measures that improve stability
- Calculate concentrate cost from the price per kilogram and the dosage
- Interpret the cost components in the price of a perfume bottle realistically
A formula that smells perfect in the lab can darken after a summer in a sunny shop window, turn cloudy when it freezes in transit, or react with the pump gasket. A professional perfume has to stay the same not just on day one but throughout its shelf life.
Why does a perfume change?
- Oxidation: Citrus terpenes (such as limonene) and linalool oxidize on contact with air; the scent goes stale, and the hydroperoxides that form can increase the risk of skin sensitization.
- Light: UV light breaks down or discolors certain molecules. Clear bottles and colored perfumes are the most vulnerable.
- Discoloration: Vanillin and ethyl vanillin can turn yellow and then brown over time; indole and some amines darken. Methyl anthranilate forms Schiff bases with aldehydes, giving a yellow-orange color.
- Reaction with alcohol: Aldehydes can form acetals with ethanol, which alters the scent somewhat during maceration (sometimes a welcome rounding-off).
- Precipitation and haze: Waxy absolutes and poorly water-soluble components can precipitate in the cold, which is why chilling and filtering are part of production.
- Packaging interaction: Some molecules migrate into plastic parts or gaskets, and some gasket materials add a foreign note to the scent.
Accelerated testing
- Reference sample A sample from the same batch is stored cool and dark (often in a refrigerator). Every other sample is compared against it.
- Heat Samples are kept in an oven at 40–45 °C. High temperature speeds up chemical reactions and exposes weak points early.
- Light A sample in its final packaging is placed in a UV cabinet or on a sunny windowsill; changes in color and scent are monitored.
- Freeze-thaw cycles The sample is moved back and forth between the freezer and room temperature for several cycles; haze, sediment and separation are checked.
- Packaging compatibility Testing is done with the actual bottle, pump and cap; weight loss, leakage, gasket swelling and changes in scent are recorded.
- Periodic evaluation Typically at months 1, 2 and 3, the scent (on a mouillette), color and clarity are compared with the reference.
Formula measures
- Antioxidants (such as BHT, tocopherol)
- UV filters in colored perfumes
- Balancing color-forming materials
- Terpeneless citrus oils
Packaging measures
- Dark or opaque glass, an outer box
- Compatible pump and gasket materials
- Minimal headspace
- Leak-proof crimp pump
What to avoid
- Testers sitting in a sunny shop window
- Stock left in a hot car
- Large bottles left open
- Packaging changes without testing
Formula cost
Fragrance houses sell concentrate by its price per kilogram. That price is the sum of each raw material's share in the formula multiplied by its own price per kilogram (plus manufacturing and margin). A few grams of natural orris or jasmine absolute can cost more than dozens of grams of an inexpensive synthetic molecule.
- Hypothetical example: A 50 ml EDP holds about 41 g of liquid (ethanol is less dense than water).
- If the concentrate dosage is 18%, the bottle contains about 7.4 g of concentrate.
- If the concentrate costs 100 units per kilogram, the fragrance cost in the bottle is about 0.74 units.
- If the same formula is written with materials at twice the price, or the dosage is doubled, the fragrance cost doubles too.
This simple calculation explains a well-known fact of the industry: in mass-market perfumes, the cost of the liquid in the bottle is usually a small fraction of the retail price. Most of the price is split among the bottle, cap and box, marketing and advertising, distribution, and the retail margin. Niche brands generally have higher concentrate budgets and dosages, but even there the liquid does not account for the whole price.
- 40–45 °C Common oven temperature in accelerated testing
- 1–3 months Typical duration of accelerated testing
- 30 months In the EU, a durability date is required below this; above it, the PAO symbol
- Stability
- The ability of a product to remain unchanged over time in scent, color, clarity and compatibility with its packaging.
- Accelerated test
- A test that applies heat, light and temperature cycles to simulate aging in a short time.
- Schiff base
- A compound, usually yellow-orange, formed by the reaction of an aldehyde with an amine such as methyl anthranilate.
- PAO
- Period After Opening: the open jar symbol showing how many months a product can be used after opening.
- Price per kilogram
- The selling price of the concentrate per kilogram; given in briefs as the cost ceiling.
- Dosage
- The percentage by weight of concentrate in the finished product.
Key points
- Perfumes can change because of oxidation, light, reaction with alcohol, precipitation and packaging interaction.
- Vanillin, ethyl vanillin, indole and Schiff bases are well-known sources of discoloration.
- Accelerated tests (40–45 °C, light, freeze-thaw, packaging) usually run 1–3 months; they are industry practice, not law.
- Concentrate cost = dosage × price per kilogram; expensive naturals in the formula raise that price considerably.
- In mass-market perfumes, the cost of the liquid is usually a small fraction of the retail price.
Sources
- Colipa & CTFA (2004). Guidelines on Stability Testing of Cosmetic Products.
- Sell, C. S. (ed.) (2006). The Chemistry of Fragrances: From Perfumer to Consumer, 2nd edition. Royal Society of Chemistry.
- Calkin, R. R. & Jellinek, J. S. (1994). Perfumery: Practice and Principles. Wiley.
- Regulation (EC) No 1223/2009, Article 19 (labelling) and Annex I (Cosmetic Product Safety Report).