In short
Store perfume materials somewhere cool and dark, in tightly closed containers kept as full as you can, with clear labels and dates. Heat, light and air are what degrade them. Oxidation matters for more than smell: some oxidized terpenes are recognized skin sensitizers, so an old citrus oil is both a poorer and a riskier material.
What you will learn
- Name the four things that make materials deteriorate
- Set up storage suited to a small collection
- Recognize signs that a material should be retired
Before this lesson: Perfume Dilution Basics: Make Your First 10%
What makes materials go off
| Cause | What happens | What to do |
|---|---|---|
| Oxygen | Oxidation changes the smell, and can form sensitizing products | Close tightly. Reduce headspace by decanting into smaller bottles. |
| Light | Drives chemical change and discoloration | Use amber or aluminum containers, in a closed cupboard or box. |
| Heat | Speeds up all these reactions | Keep away from radiators, windows, and hot rooms. |
| Contamination | Water, other materials and dirty tools spoil a whole bottle | Use clean tools. Never return leftovers to a stock bottle. |
The owner's version of this question, keeping a bottle of perfume, is covered by the RUŌOD Journal guide to storing perfume. Raw materials need more care than a finished perfume, partly because you open them far more often. For how long particular types of material tend to last, read the reference guide on raw material shelf life.
Why oxidation is a safety issue too
Terpenes such as limonene and linalool react slowly with oxygen in the air. In research on this, the hydroperoxides that form are treated as the main suspected sensitizers. One study found that pure linalool caused no reactions in guinea pigs while linalool oxidized for ten weeks did sensitize them, and patch-test work in people has reported reactions to oxidized terpenes in dermatitis patients. These findings are about specific materials and test conditions, and they do not give you a rule for judging your own bottle. They do give you one more reason to look after citrus and other terpene-rich oils, and a good reason to replace them rather than use them indefinitely.
Containers
- Glass, amber if possible, with a tight cap suited to oils and solvents. Aluminum is common for larger volumes.
- Avoid most plastics for long-term storage, as many fragrance materials attack or pass through them. Check with your supplier when in doubt.
- Keep it small. As a bottle empties, decant it to a smaller one. Copy over the whole label: material, supplier, lot number and date.
- Do not leave droppers in bottles. Rubber bulbs can degrade and contaminate an oil.
Should you use a refrigerator?
Keeping materials cold slows deterioration, and many perfumers refrigerate citrus oils. If you do, use a separate fridge, or at least sealed secondary containers, and never share a shelf with food. Ordinary domestic fridges are not designed for flammable vapors, so keep quantities of alcohol-based dilutions out of them unless the appliance is suitable. Let a cold bottle reach room temperature before you open it, so that water does not condense inside. Some materials also solidify or cloud when cold, so check how each one behaves. A cool, dark cupboard is a perfectly good choice for a small study collection.
Dilutions age as well
A dilution exposes a material to solvent and often more air, and it is opened often. Make small amounts, write the date on the label, and remake them when they begin to change. If you compare a fresh dilution with an old one, you may be surprised.
When to retire a material
Dates help but they are not the whole answer, since the same material can age differently under different conditions. Consider replacing something when:
- it smells sharper, flatter, more turpentine-like or rancid than your notes describe;
- it has darkened or become cloudy or thicker than it was, unless that is known to be normal for the material;
- it has passed the supplier's stated shelf life, particularly citrus and other terpene-rich oils;
- its label is missing or unclear. If you cannot identify it for certain, you should not use it.
Dispose of retired materials according to local rules and the SDS. Do not pour them down the drain.
Practical exercise: Set up storage and a stock log
- Gather everything you own into one place, and check each label. Throw nothing away yet.
- Make a stock log with columns for material, type, supplier, lot number, date received, date opened, amount, location and SDS location.
- Move your materials into a closed box or cupboard away from heat, light, food, children and pets.
- Smell any oil older than a year alongside your notes or a fresh sample if you have one, and record what you find.
- Choose your review date, perhaps every three months, and put it in your calendar.
A spreadsheet works for this log, and our guide to a raw material inventory suggests more columns as your collection grows. The RUŌOD Lab app can also keep custom fields such as dates and locations on a material record.
You have done this well if each bottle can be matched to its inventory row, each row has a date and a storage location, and you have marked which materials to check first for aging.
Common mistakes
- Displaying bottles on an open shelf. They look lovely, and the light is ruining them.
- Keeping everything in its large original bottle. The air above the liquid grows as you use it.
- Keeping old citrus oil because it is still half full. It may no longer be what it was, in smell or in safety.
- Trusting your nose alone for safety. You may not smell what oxidation has formed. Use dates and supplier guidance too.
Safety
Store flammable materials and alcohol in small quantities, away from heat and ignition sources. Local fire codes can apply to quantities and storage. Do not store materials in containers that could be mistaken for food or drink.
Key terms
- Oxidation
- Chemical change caused by reaction with oxygen, which can alter a material's smell and in some cases raise its potential to cause skin allergy.
- Headspace
- The air above the liquid in a container. Larger headspace means more oxygen in contact with the material.
- Autoxidation
- Slow, spontaneous reaction with oxygen in air. Terpenes such as limonene and linalool are known to undergo it.
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.