Beginner perfumer · 23
Should you add glycerin: it is not useless, it is in the wrong product
· 28 min read
A thread listing beginner myths included "you need to add water, glycerin, etc", and a reply said nobody has ever claimed that — to which another reply said you have not hung around here enough. I counted: 3 of 91 posts in one week on that sub asked about it. The database answers more directly. Glycerin's odour field says odourless, its strength field says none, its longevity field is blank, and it is classified as a solvent rather than a fragrance material. Its logP is −1.80, against a median of +3.0 across 1,465 materials with longevity records.
Someone on r/DIYfragrance started a thread listing beginner myths, and one of them was "you need to add water, glycerin, etc".
A reply disagreed:
"Likewise, never ever have I ever heard anyone ever say that you need to add water, glycerin, etc into a formula… they're equally just such obvious, plain BS?"
Another reply answered it in one line:
"If you've not heard people say you need glycerin or water you've not hung around here enough."
That disagreement is settleable. Someone on the same sub once tallied a week of posts by category: 3 of 91 posts asked about whether to use water, glycerin, DPG or dupe oils. Searching that sub for "glycerin" turns up two dozen threads.
So the second reply is right. What this article answers is not whether people say it, but why it is wrong and where glycerin actually belongs.
The short version
- How the database records glycerin: odour "odourless", strength "none", longevity blank, classified as a solvent or diluent for cosmetic, flavour and fragrance agents. It is not a fragrance material.
- Glycerin's logP is −1.80. Across the 1,465 materials carrying an odour classification, a longevity record and a logP, the median is +3.0, with 1,382 (94.3%) at +1 or above. Exactly one material is more hydrophilic than glycerin, and it is xylose — a sugar.
- A gap of 4.8 log units means roughly a sixty-thousand-fold difference in oil-water partitioning. Any fixative effect requires the fragrance to dissolve in the additive first, and that gap is why it does not.
- It is not useless. Glycerin in skin has a literature: it exists in the stratum corneum as an endogenous humectant, and standard basic emollients pair humectants like glycerol with occludents like petrolatum.
- Its place is in products containing water — body mists, hair perfumes, aftershaves. In a straight alcoholic concentrate it has no job to do.
About a 9 minute read.
How the database sees the three
Put glycerin, DPG and phenoxyethanol side by side and the difference is immediate.
| Glycerin | DPG | Phenoxyethanol | |
|---|---|---|---|
| CAS | 56-81-5 | 25265-71-8 | 122-99-6 |
| Database category | Solvent (cosmetic/flavour/fragrance) | Solvent (flavour/fragrance) | Fragrance agent |
| Odour | Odourless | None | Rose, balsamic, cinnamyl |
| Strength | None | None | Medium |
| Longevity record | Blank | 400 hours | 84 hours |
| logP | −1.80 | −0.60 | +1.20 |
| Boiling point | 290 °C | 230 °C | 237 °C |
| Suppliers | 64 | 37 | 46 |
Look at the longevity row. DPG records 400 hours and phenoxyethanol 84, and glycerin's is empty.
DPG's 400 hours is worth a pause on its own. It has no odour, yet it sits on a blotter for 400 hours. That is a clean demonstration that lasting and smelling are two different measurements. A non-volatile, odourless thing sitting on paper does not make your perfume smell for longer.
And one supplier description for phenoxyethanol reads: due to its low evaporation, phenoxyethanol is used as a fixative in perfumes and fragrance. Note how it differs from glycerin — it has its own odour, a longevity record, and a positive logP. It dissolves in the concentrate.
That 4.8 log units
Pulling the database materials that carry an odour classification, a longevity record and a logP together gives 1,465 of them:
| logP | |
|---|---|
| Median | +3.00 |
| Mean | +2.99 |
| Lowest | −2.50 (xylose) |
| Highest | +9.60 |
| At logP ≥ +1 | 1,382 (94.3%) |
| Below logP 0 | 13 (0.9%) |
| More hydrophilic than glycerin (−1.80) | 1 |
That one is dextro-xylose, a sugar. It is in a fragrance database because it has a taste record, not because anyone perfumes with it.
So glycerin is more hydrophilic than 1,464 of 1,465 fragrance materials. Median +3.0 against −1.80 is 4.8 log units, which as a partition ratio is 10^4.8, about sixty thousand fold.
LogP measures octanol-water partitioning, which is not identical to whether glycerin dissolves a given aroma chemical, but the two share a cause: two liquids this far apart in polarity do not mix. And every fixative mechanism starts with the fragrance molecule staying in the medium. Without that step there is no mechanism.
A formula that separates
The thread had a real failure case. Someone making their first fragrance asked why it kept separating five to ten minutes after shaking. They posted the formula:
| Material | Amount |
|---|---|
| Jojoba oil | 77.75 mL |
| Vanilla oleoresin | 10.0 mL |
| Sandalwood fragrance | 3.0 mL |
| Cinnamon cassia | 2.5 mL |
| Lavender, clary sage, benzoin | 2.0 mL each |
| Nutmeg | 1.0 mL |
| Vegetable glycerin | 0.25 mL |
They guessed it was the vanilla.
That 0.25 mL of glycerin is the likelier culprit. It is 0.25% of the bottle, a small amount, but its polarity gap against jojoba oil is wide enough that it will not mix — so it settles out as a visible layer or as beads. Shaking disperses it, standing lets it coalesce again, and the timescale for that is minutes.
It went in to make the fragrance last longer, and what it produced was separation. That is this whole article in miniature.
What a proven fixative claim looks like
One reply in the thread put it more carefully than a flat "fixatives don't exist":
"For beginners, I think a good rule of thumb is that there is 'no such thing as a fixative' as it can lead the naïve astray — but in fact I have reason to suspect there are some ingredients that definitely can exert influence on the evaporation of others, though this is mostly not to any extreme amount it is still useful."
The mechanisms named are hydrogen bonding and van der Waals forces. That is correct, and it is the position of our own article on evaporation: evaporation is governed by vapour-liquid equilibrium and activity coefficients rather than by anything holding anything, while components do influence each other — just not by as much as the folklore says.
So what would an experiment demonstrating that an additive really slows evaporation look like? One from 2018 shows you.
Cabin-Flaman and colleagues, in the International Journal of Cosmetic Science, tested whether zein — a film-forming maize protein — retains fragrance. They added corn zein to eugenol in a hydro-alcoholic solution to form a film both in vitro and on human skin, tracked eugenol trapping and release by GC/MS, and labelled the eugenol with deuterium so they could image its distribution inside the film by secondary ion mass spectrometry (NanoSIMS 50).
Eugenol evaporation split into three periods. The first (2 hours or less) was simultaneous solvent and eugenol evaporation during film formation. The second (about 10 hours) was continuous slow eugenol evaporation, but not to completion. The third (at least out to 48 hours) came from eugenol trapped in the film — and after 24 or 48 hours that trapped eugenol could be released and evaporated under mechanical deformation of the film. They separately confirmed that zein does not favour eugenol penetration into the viable epidermis, so it does not raise sensitisation risk.
That is what a retention claim looks like when it has been demonstrated: molecular-level location imaging, a time-resolved release curve, and a safety control.
I found no study doing comparable work on glycerin. That does not prove glycerin has no effect, but it does mean the claim currently rests on repetition rather than on data.
Glycerin's real job is on skin
Everything above is about what glycerin does not do. What it does do is documented, and more interesting than most people assume.
Verdier-Sévrain and Bonté, in the Journal of Cosmetic Dermatology in 2007, reviewed the molecular mechanisms of skin hydration. Water retention in the stratum corneum depends on two components: hygroscopic agents inside the corneocytes, collectively the natural moisturizing factor, and the intercellular lipids arranged in order to form a barrier against transepidermal water loss.
One finding is worth keeping: glycerol, a well-known cosmetic ingredient, exists in the stratum corneum as a natural endogenous humectant. The same review covers the discovery of the water-transporting protein aquaporin-3 in the viable epidermis, and of tight junction structures at the stratum granulosum boundary, both of which reshaped understanding of how skin distributes water.
Fluhr and colleagues, reviewing basic emollients in the International Journal of Dermatology in 2025, state the practice plainly: basic emollients are typically formulated with humectants to improve hydration and water-holding capacity (glycerol, urea, lactic acid) and occludents to restore the epidermal barrier (petrolatum, liquid paraffin). They remain the standard of care for long-term management of dry skin.
So glycerin is not a useless ingredient; it is a workhorse in skincare. Its working material is simply water, not fragrance molecules. Adding it to a straight alcoholic concentrate is hiring a plumber to tune a piano.
When you can add it
There is one class of products where glycerin has a place: products containing water.
- Body mist and hair perfume. These already have a water phase, and glycerin does its humectant job inside it. Someone in the thread asked about diluting perfume with water and glycerin to make a hair mist, which is the right direction — but note that concentrate mostly will not dissolve in a low-alcohol, high-water medium without a solubiliser, and a water phase needs preservation.
- Aftershave. A formula in the thread ran 43% alcohol, 22% witch hazel, 22% distilled water, 13% glycerin. That is a cosmetic formula rather than a perfume formula, and the glycerin is there to offset the alcohol's drying effect. Thirteen percent is the order of magnitude, not the 0.25% you see in perfumes.
The pattern: where there is water, glycerin runs at double-digit percentages and its target is skin. Where there is no water, its amount is zero.
For straight alcoholic concentrates, alcohol is already an excellent solvent, and that article covers what to dilute with and in what order.
What this doesn't establish
LogP is not solubility. The octanol-water partition coefficient is related to whether glycerin dissolves a given aroma chemical, but it is not the same quantity. I used it because it is the polarity indicator with good coverage in the database, and a 4.8-log-unit gap supports the directional conclusion that these two do not mix — not any precise solubility figure.
Those 1,465 are a conditioned subset. The condition is carrying an odour classification, a longevity record and a logP together. The database holds 42,225 materials, so this is a small subset biased toward the thoroughly documented ones rather than the distribution of all fragrance materials.
"I found no comparable study on glycerin" is my search result, not proof of absence. I searched PubMed on glycerol, evaporation and aroma release. Industry internal data is not visible to me.
The diagnosis of that separating formula is inference. I do not have the bottle; I named glycerin as the likeliest cause from the polarity gap. Vanilla oleoresin can also drop resin out of solution.
"Glycerol is in the stratum corneum" does not mean applying glycerin replenishes it. Both papers describe emollient mechanisms, with doses, dosage forms and indications set in a dermatological context that does not transfer straight into perfume formulation advice.
References
S. Verdier-Sévrain, F. Bonté, Skin hydration: a review on its molecular mechanisms, Journal of Cosmetic Dermatology, 6(2), 75–82 (2007). PMID 17524122. doi:10.1111/j.1473-2165.2007.00300.x
J. W. Fluhr, V. Muguet, S. Christen-Zaech, Restoring Skin Hydration and Barrier Function: Mechanistic Insights Into Basic Emollients for Xerosis Cutis, International Journal of Dermatology, 64(Suppl 1), 5–12 (2025). PMID 40231699. doi:10.1111/ijd.17790
A. Cabin-Flaman et al., Effect of zein additive on perfume evaporation, International Journal of Cosmetic Science, 40(6), 575–582 (2018). PMID 30414278. doi:10.1111/ics.12500
Related: Fixatives do not hold anything, Solvents are not background, Two ways to measure longevity, Maceration and water.