How to make an eau de cologne

An eau de cologne is a light citrus-aromatic perfume at low strength: mostly citrus and herbs with a little neroli or lavender, a thin base, and a small share of concentrate in alcohol. It is the quickest perfume to make and the quickest to fade. Two things decide whether it works: the citrus grades, because expressed citrus oils are phototoxic, and the expectation, because a cologne is meant to last a couple of hours.

How strong is an eau de cologne?

Weak by design. When you start a formula, PerfuMate's "What are you making?" choice sets a cologne at 5 percent concentrate and an eau de toilette at 10; the free IFRA calculator uses the same two presets. A citrus composition does not get louder with more concentrate: PerfuMate's wear model puts its loudest point at about 6 to 9 percent, and past that the extra concentrate buys a little more time, not more brightness.

Which citrus oils should a cologne use?

Grades without the phototoxic furocoumarins, or small amounts of those that have them. Expressed citrus oils carry bergapten, which reacts with sunlight on skin, and IFRA caps them for that reason.

• Bergamot: Bergamot FCF Essential Oil, with the furocoumarins removed, instead of ordinary Bergamot Essential Oil.
• Lemon: Lemon Essential Oil is cold pressed and capped; Lemon Essential Oil Distilled and the FCF grade are marked in the catalog as exempt from the phototoxic cap.
• Lime: Lime Essential Oil Distilled is not phototoxic; the expressed oil is capped.
• The orange tree: Petitgrain Bigarade Essential Oil and Neroli Essential Oil give the classic cologne middle.
• The herbs: Rosemary Essential Oil and Lavender Essential Oil make it aromatic rather than just fruity.

An FCF or distilled grade is not a free pass: its linalool, limonene and citral still count toward their own limits and the allergen label. Phototoxic perfume ingredients lists the rest.

What is a good first cologne formula?

A concentrate of 20 g, weighed in this order, heaviest first:

1. Ethylene Brassylate: 2 g
2. Iso E Super: 1 g
3. Hedione: 3 g
4. Lavender Essential Oil: 2 g
5. Rosemary Essential Oil: 1 g
6. Neroli Essential Oil: 1 g
7. Petitgrain Bigarade Essential Oil: 2 g
8. Lemon Essential Oil: 3 g
9. Bergamot FCF Essential Oil: 5 g

Hedione adds a transparent jasmine lift; Iso E Super and Ethylene Brassylate are a small, soft base so the cologne does not end in nothing. Checked in the IFRA calculator at 5 percent, this formula is within every IFRA Category 4 limit of the 51st Amendment. The line that sets its ceiling is the cold-pressed lemon, and the engine finds it stays within every limit up to 13.33 percent, far above a cologne.

Swap the FCF bergamot for ordinary expressed Bergamot Essential Oil and the same cologne at 5 percent puts bergamot at 1.25 percent of the finished product against a cap of 0.4, more than three times over; the highest strength it would pass at is 1.6 percent. Use Lemon Essential Oil Distilled in place of the cold-pressed oil and the engine finds no strength at which the formula fails.

How much alcohol does a cologne take?

Almost all of the bottle. Alcohol weighs about 0.8 g per ml, so a 100 ml bottle holds about 80 g. At 5 percent that is 4 g of the concentrate and 76 g of Perfumer's ethanol. The 20 g concentrate above makes five such bottles, or one bottle and room to try the others at 8 and 10 percent. A light citrus cologne tolerates a little water better than any other perfume, but add it to a small test bottle first and watch for haze. Why a perfume turns cloudy.

How long should a cologne rest?

About two months. PerfuMate's maceration journal gives anything up to 15 percent a 60 day rest, with four dated checks: shake and aerate on day two, a first blotter on day seven, a smell check at the halfway point, and at the end, chill for a day and filter before bottling. Citrus oils oxidize, so keep the bottle full, sealed, cool and dark.

Why does a cologne fade so fast?

Because it is mostly top notes at a low strength, and top notes are the materials that leave first. Citrus is readable on a strip for a few hours at most, and on skin for less. PerfuMate's wear model puts an all-citrus cologne at 12 percent at a little over two hours before it falls below notice, and the model's reference range for a cologne is two to four hours on skin. That is the genre, not a fault: a cologne is splashed on and renewed.

A fixative will not change it much, because no fixative makes a citrus last (what a fixative can and cannot do). To stretch it, give it a slightly larger base or move up toward eau de toilette strength, and accept that each step makes it a little less of a cologne.

PerfuMate keeps the grams, the percentages and the IFRA check in step while you compose, flags the expressed citrus grades against their caps, and dates each batch's rest in the maceration journal. How to make perfume at home covers the rest of the bench. Start a formula, free.