A vial of accord, a bottle of alcohol, a bottle of jojoba, a dark cupboard. Lesson seven of the blending course takes the blend from blotter to bottle: dilute to a ratio, rest it for weeks in the dark, then chill and filter.
From blotter to bottle
The previous six lessons worked on paper. The rose and patchouli accord of lesson four, the modifiers of lesson five, the fixatives of lesson six were all judged on blotters at smelling dilution. The final blend of oils, before it goes into alcohol or oil, is what perfumery calls the perfume concentrate, or jus.
Neat concentrate is not used directly on skin. It has to be diluted into a solvent or a base at a ratio worked out in advance. That ratio decides what the finished bottle is: an alcohol perfume, a perfume oil, or a body oil.
Moving into a bottle adds two materials that the blotter lacked. The first is the solvent, alcohol or carrier oil, each carrying scent in its own way. The second is time. A blend fresh from mixing and a blend rested for some weeks give two different scents, even with the same formula.
This lesson goes through each step in order: choose the base, calculate the concentration, check the limits, rest, filter, label. Each step leaves a line in the scent notebook, and those lines are the material for lesson eight.
Alcohol or carrier oil
Perfumer's alcohol is high strength ethanol, usually denatured under each country's rules. According to the library's glossary, the denaturant is chosen to interfere as little as possible with odour. Blending 101 gives eau de parfum at 15 to 20 percent in 90 degree alcohol. The alcohol leaves the skin in the first minutes, leaving the blend of oils behind.
Carrier oil is the second choice. Carrier oils are plant based and do not evaporate. The library's vegetable oils page notes that jojoba is actually a liquid wax ester, not a triglyceride, and resists rancidity thanks to its high tocopherol content. Jojoba is therefore the usual base for perfume oil; Blending 101 gives perfume oil at 15 to 30 percent in jojoba.
The two bases are not interchangeable for every formula. Lesson six noted that benzoin does not dissolve in carrier oils. An accord with benzoin goes smoothly into alcohol but may leave a residue in jojoba. Other thick resinoids and absolutes also need a solubility test before the base is chosen.
The base also changes how the scent appears. In alcohol, the top lifts as the alcohol evaporates. In oil, there is no solvent leaving to carry the light part up, so the scent opens more slowly and stays closer to the skin. One jus, two bases, two different bottles, and both should be dipped on blotters side by side.
Concentration and dermal limits
Concentration is the share of jus in the finished bottle. The library's formula calculator gives an example: a 50 ml batch at 20 percent holds 10 ml of jus and 40 ml of alcohol or carrier. Familiar levels such as eau de parfum at 15 to 20 percent or extrait at 20 to 30 percent are trade conventions, not legal standards.
For products spread widely on skin, dilution is much lower. Blending 101 gives 1 to 3 percent for body lotion, 0.5 to 1 percent for the face, no more than 1 percent in pregnancy. From the same jus, a perfume and a body oil can differ tenfold in concentration.
Total concentration is not enough. Each oil in the jus has to be checked against its own limit. Take the accord from lesson four: damask rose has a maximum dermal level of 0.6 percent in the library's data, because it contains methyleugenol. At 15 percent concentration, rose can make up no more than 4 percent of the jus. The 7:3 ratio from the series has to be rewritten on its way into the bottle.
IFRA divides products into 12 categories, each with its own limits: category 4 is fine fragrance, category 5A is body lotion. For methyleugenol the library gives an IFRA limit of 0.02 percent for fine fragrance and 0.0004 percent for body lotion. Cold pressed bergamot has a limit of 0.4 percent in leave-on products exposed to sun; the FCF grade, with bergapten removed, is not bound by it. The library's Safety page gathers the general rules; the formula calculator does not check these limits itself.
Darkness and a few weeks of waiting
A blend of jus and alcohol fresh from mixing is not yet the final scent. The library's glossary calls the rest period that follows maceration: usually days to weeks, before chilling and filtering. The scent settles and knits together during this time. Blending 101 gives eau de parfum 2 to 4 weeks of aging.
During maceration the constituents keep interacting with each other and with the solvent. One example appears in the glossary: an aldehyde meeting an alcohol can form an acetal, which usually smells softer than the parent aldehyde. Not every change is visible, but a blotter at week three usually differs from a blotter on day one.
The conditions for resting come from the library's storage page. Light, especially UV, generates free radicals and speeds oxidation; sweet orange oil exposed to UV for 50 minutes develops piperitone, photocitral A and at least a dozen other new constituents. Heat speeds almost every reaction. Water hydrolyses esters, turning linalyl acetate into linalool and acetic acid.
The resting bottle should therefore be dark glass, amber or cobalt, tightly closed, in a cool dark cupboard. The empty space in the bottle should be as small as possible, since oxygen takes the place of the liquid that has gone. Once a week it can be opened, a blotter dipped, the date and description noted, then closed at once.
Chill filtering and clarity
After maceration some alcohol perfumes turn hazy in the cold. The cause is material with poor solubility in alcohol: waxes, heavy fractions of oils and resins. Bulgarian damask rose, for example, contains 19 to 24.5 percent alkanes and alkenes, waxy molecules present naturally in the oil.
Perfumery deals with this by chilling and filtration. The matured perfume is cooled so that waxes and poorly soluble matter precipitate, then the precipitate is filtered out. The library's glossary notes that this step keeps the product clear and prevents haze in the cold.
For a single bottle made at home the step can be simple: place the bottle in the refrigerator, wait for the haze to settle, then pour through clean filter paper into another dark bottle. The residue should be smelled on a blotter before it is discarded. If the residue carries a lot of scent, the next version can reduce the clouding material or use a different form of it.
Perfume oil in jojoba rarely meets this problem in the same way, but jojoba can thicken in the cold. With oil, the check is to bring the bottle back to room temperature and see whether any residue remains. Residue that stays after warming is usually undissolved material, such as benzoin in oil.
Labelling a home made bottle
A bottle without a label is a bottle that cannot be made again. The label of a home made bottle needs at least six lines: formula name, date of mixing, base alcohol or oil, jus concentration, date of filtering, and the list of oils with their shares. The list links the bottle to its page in the scent notebook.
The label is also where cautions for use are written. If the jus contains an oil contraindicated in pregnancy, such as the myrrh of lesson six, that line belongs on the label. If it contains cold pressed bergamot, it should say to avoid sun after application. If it is a test meant only for blotters, the label should say so.
For products that are sold, the rules go further. According to the library's data, the EU requires fragrance allergens such as linalool, geraniol and citronellol to be declared above 10 ppm in leave-on products and 100 ppm in rinse-off products. Regulation (EU) 2023/1545 extends the list, including patchouli oil and bergamot oil.
After lesson seven, the first bottle stands on the shelf. Its formula is still written in drops. Lesson eight, the last of the course, rewrites that formula in grams and percent, checks each material against its limit, and costs this very bottle.
Alcohol carries a scent away. Oil keeps it close to the skin. Darkness leaves it still.
A perfume is made twice: once when mixed, once while it waits.
No one sees the waiting.