A clear, lightly scented water — toner, body mist, micellar water, wet-wipe lotion — is the cheapest product in the catalogue to formulate and the one most often reworked. The fragrance is rarely the problem. The problem is that the solubilizer dose was copied from a supplier table that never said which fragrance it referred to.
Search hard enough and you will find starting ratios for the same polysorbate quoted as 1:1 to 3:1, as 3:1 to 5:1, and as 3:1 to 10:1 by weight. All three are correct. They were measured on different fragrances. This article puts the missing variable — fragrance polarity, expressed as logP — back into the calculation, and treats the number on the table for what it is: a starting point that belongs to someone else's oil.
Clear and cloudy are two physical states, not two settings of one dial
The difference is droplet size, and it spans four orders of magnitude. A solubilized fragrance sits inside surfactant micelles 10–100 nm across. A conventional emulsion carries droplets 1–100 µm across. Visible light has a wavelength of roughly 400–700 nm, so the micelle is below the scattering threshold and the system looks clear, while the emulsion droplet scatters strongly and looks milky.
This has one hard practical consequence: no amount of extra emulsifier converts the second state into the first. Adding emulsifier to a milky system makes the droplets finer and the haze slightly softer; it does not make the product transparent. Clarity has to be designed in before the batch exists — solubilizer chosen, ratio calculated, process sequence fixed. Once a fragrance has been dumped into water and dispersed as coarse droplets, the batch is usually written off rather than rescued.
Three published ratio tables, three different answers
Here is the same polysorbate family, quoted by four different technical sources for what sounds like the same job:
| Source and system | Quoted ratio (solubilizer : fragrance) | What it was measured on |
|---|---|---|
| Supplier A, Polysorbate 20, fragrance oils | 1:1 to 3:1 | General fragrance oils, starting point |
| Supplier B, Polysorbate 20, essential oils and fragrance | 3:1 to 5:1 | Working ratio quoted as a guarantee of clarity |
| Supplier C, PEG-40 Hydrogenated Castor Oil | 3:1 to 10:1 | Range spanning light fragrances to pesticide actives |
| Supplier D, PEG-40 Hydrogenated Castor Oil, essential oils | 3:1 to 5:1 | Typical clear cosmetic systems |
Part of the spread is bookkeeping — one source reports the ratio at which clearing begins, another the ratio at which clearing is guaranteed across a temperature range. The rest of the spread is chemistry, and it collapses into a single variable: how hydrophobic the fragrance is.
| Fragrance molecule | Typical role in a blend | logP | Water solubility |
|---|---|---|---|
| α-Pinene | Turpentine, conifer top note | 4.83 | Very low |
| Limonene | Citrus top note | 4.57 | 13.8 mg/L |
| Geraniol | Rose middle note | 3.56 | Low |
| Linalool | Lavender middle note | 2.97 | 1.6 g/L |
| Vanillin | Vanilla base note | 1.21 | About 10 g/L |
Each logP unit is a tenfold change in octanol–water partition. Between limonene at 4.57 and vanillin at 1.21 there are more than three orders of magnitude of water affinity, and the micelle volume needed to hold them moves by roughly the same factor. That is why a citrus accord and a vanilla accord, both dosed at 0.5%, can need 5:1 and 1.5:1 respectively.
A real fragrance is a mixture of 20 to 80 such molecules, in which case the number that matters is not the average but the extreme: clarity is set by the most lipophilic few percent of the blend. This is why adding a single woody or musky base note to an otherwise well-behaved floral can push a clear toner into haze without changing the total fragrance percentage at all. When a formula clouds and the fragrance load has not moved, ask which component changed, not how much was added.
HLB differs by 1.7 points; the load differs by a factor of two
If HLB decided solubilization, Polysorbate 20 (HLB 16.7) and Polysorbate 80 (HLB 15.0) would be nearly interchangeable. In practice PS20 is the default for clear fragrance systems and PS80 is the fallback, and the reason is structural rather than numeric. The laurate tail (C12, saturated, short) packs into micelles of high curvature with a compact, well-defined hydrophobic core that stays optically clear. The oleate tail (C18:1, long, unsaturated, kinked) produces larger and looser aggregates — excellent at stabilising emulsion droplets, prone to haze when asked to solubilize.
HLB was designed as an emulsifier-selection parameter. It correlates with interfacial curvature and with the required HLB of an oil phase; it says nothing about the volume of oil a micelle can swallow. Using it to choose a solubilizer is using the wrong instrument, and it explains a common failure: two grades with HLB values a point and a half apart, one of which clears the batch and one of which does not.
The five polysorbates on one table
| Grade | Fatty acid | HLB | Form at 25 °C | SV calculated | SV specification | Hydroxyl value | Best use |
|---|---|---|---|---|---|---|---|
| Polysorbate 20 | Laurate (C12) | 16.7 | Viscous liquid | 45.7 | 40–50 | 96–108 | Default for clear aqueous fragrance |
| Polysorbate 40 | Palmitate (C16) | 15.6 | Liquid to soft paste | 43.7 | 41–52 | 90–107 | Intermediate; rarely first choice |
| Polysorbate 60 | Stearate (C18) | 14.9 | Paste | 42.8 | 45–55 | 81–96 | Cream O/W bodies; awkward cold |
| Polysorbate 80 | Oleate (C18:1) | 15.0 | Viscous liquid | 42.8 | 45–55 | 65–80 | Heavy oils, food and pharma standard |
| Polysorbate 85 | Trioleate | 11.0 | Viscous liquid to paste | 91.5 | 83–98 | 40–60 | Co-emulsifier, not a solubilizer |
Two readings are worth taking from this table. The first is that the saponification value separates the tri-ester from the four mono-esters by a factor of two — 91.5 against 43 to 46 — because the molecule carries three ester bonds instead of one. But among the four mono-esters the calculated values span less than three units, which is inside the method error: a saponification value cannot tell you whether you were shipped PS20 or PS60.
The second is that the hydroxyl value can. Free hydroxyls fall as the fatty acid gets longer and as esterification deepens, giving five windows that do not overlap, from 96–108 down to 40–60. If a COA shows a hydroxyl value of 70 on a grade invoiced as Polysorbate 20, the invoice is wrong.
The calculated column uses SV = n × 56,106 / M with n = 1 for the mono-esters and 3 for the tri-ester, on nominal average molecular weights. Commercial polysorbates contain some di-ester and free PEG, so measured values often sit slightly above the calculation — which is exactly why PS60 and PS80 specify 45–55 against a calculated 42.8. Treat the calculation as an order-of-magnitude check, not as a pass-fail limit.
PEG-40 hydrogenated castor oil: the second tool, and what it costs
PEG-40 Hydrogenated Castor Oil (CAS 61788-85-0) is the other workhorse of this application. HLB 14–16, cloud point 65–75 °C as a 1% aqueous solution, CMC roughly 0.1–0.5 g/L, pH 5–7 in 1% solution, low foaming, working ratio 3:1 to 5:1 by weight for clear systems, typical use level 0.5–5%.
Its hydrophobe is not a single fatty acid but a hydrogenated castor-oil triglyceride — three C18 chains plus residual hydroxyls — ethoxylated with about 40 moles of ethylene oxide. That core is bulkier and more polar than a sorbitan laurate, which is why it carries higher loads of vitamin E, silicone, UV filters and heavy floral absolutes that PS20 struggles with, and why it is the standard choice in alcohol-free perfume, clear scalp tonics and micellar waters.
The cost is thermal. Its cloud point is 65–75 °C against more than 95 °C for PS20 at the same concentration, and electrolyte pulls it lower still. A clear product filled at 50 °C, or shipped in a container that reaches 55 °C in an August crossing, has very little margin. Two specification lines matter for this grade and rarely appear on a purchase order: peroxide value no more than 5 meq/kg, because hydrogenated castor oil retains hydroxyls and residual peroxides react with fragrance aldehydes to produce off-odours; and 1,4-dioxane no more than 10 ppm, which applies to every ethoxylate on this page.
The load arithmetic
Everything in a clear system obeys one inequality: fragrance % ≤ solubilizer % ÷ ratio.
| Target fragrance load | At 3:1 | At 4:1 | At 5:1 |
|---|---|---|---|
| 0.3% | 0.9% | 1.2% | 1.5% |
| 0.5% | 1.5% | 2.0% | 2.5% |
| 0.8% | 2.4% | 3.2% | 4.0% |
| 1.5% | 4.5% | 6.0% | 7.5% |
| 2.0% | 6.0% | 8.0% | 10.0% |
Read the table the other way and it becomes a formulation constraint rather than a recipe. With a 5% ceiling on solubilizer — roughly where a toner starts to feel tacky — the maximum fragrance load is 1.67% at 3:1 and 1.0% at 5:1. If the brief calls for 2% of a citrus-forward fragrance in a base that tolerates only 5% solubilizer, no reformulating effort will close the gap at 5:1. Either the fragrance changes or the product stops being clear.
Every step up in ratio costs one additional kilogram of solubilizer per kilogram of fragrance. Because the solubilizer costs an order of magnitude less than the fragrance, the material penalty is modest; the real penalty is sensory and dimensional. More surfactant means more tack on dry-down, more foam on a filling line, and less room in the formula for humectants, actives and preservative. This is the argument for measuring the ratio on your own fragrance instead of buying a safety margin you do not need.
Four ways a clear system goes cloudy again
| Symptom | Mechanism | Countermeasure |
|---|---|---|
| Haze after cold storage at 4 °C | Solubilization capacity falls with temperature; the most lipophilic components come out first | 48 h at 4 °C plus three freeze–thaw cycles from −5 to 25 °C; set the ratio on the cold result, not the room-temperature one |
| Haze at 50–60 °C | Cloud point of the ethoxylate; 65–75 °C for PEG-40 HCO, lower in electrolyte | Fill at least 15 °C below the cloud point; assess container temperatures during shipping at 55 °C |
| Haze after adding salt or buffer | Salting-out: less free water, cloud point shifts down | Run a 0 / 0.5 / 1 / 2% NaCl ladder, with the actual preservative salt present |
| Haze band during dilution | A concentrate diluted to use strength passes briefly through a two-phase region | Test stability at the final use concentration, not on the concentrate |
| Haze and rising acid value after months | Ester hydrolysis at high temperature or extreme pH | Hold pH 4–8, avoid storage above 40 °C, watch acid value on the COA |
The dilution case deserves emphasis because it is invisible in concentrate testing. A concentrate that is perfectly clear at 10% active can throw a haze band at 2% — the concentration at which the customer actually uses it. If the product ships as a concentrate and is diluted on site, the stability protocol has to cover both ends and the path between them.
Order of addition decides the batch
Premix the solubilizer with the fragrance until uniform, then bring the water in slowly under moderate agitation. The premix guarantees the fragrance meets surfactant before it meets bulk water; the slow addition lets micelles form rather than forcing a coarse emulsion. Adding fragrance directly to the water phase produces 1–100 µm droplets first, and recovering from that state usually needs long high-shear work — in production the batch is more often written off.
No heating is required. PEG-40 HCO is a paste at room temperature and is easier to handle warmed to 40–50 °C. Polysorbate 60 is also a paste and is the awkward grade in cold processing, which is a practical reason it is rarely chosen as a solubilizer despite a respectable HLB.
Judge clarity by transmitted light rather than by colour: 100 mL in a glass bottle against a white background, plus a turbidity reading. A ceiling of 10 NTU is a workable internal definition of clear. Colour drift is a separate problem — it comes from the ethoxylate or the fragrance, not from the micelles.
Four numbers on the certificate that identify what you bought
- Saponification value — n × 56,106 / M. Separates tri-ester from mono-ester at a glance, and catches a mislabelled drum that the INCI name missed.
- Hydroxyl value — the only routine number that distinguishes PS20 from PS40 from PS60 from PS80. Five non-overlapping windows, 40 to 108.
- Acid value, no more than 2 — hydrolysis of the ester bond after ethoxylation releases free fatty acid. A rising acid value in a stored drum is a shelf-life warning, and the same hydrolysis happens in the finished product.
- Peroxide value no more than 5 meq/kg, 1,4-dioxane no more than 10 ppm, ethylene oxide not detected — the oxidative and the toxicological pair. Both are grade-defining for PEG-40 HCO in particular.
One CAS number covers a whole polymer family, not a molecule. CAS 9005-64-5 is Polysorbate 20 in general: the ethylene oxide distribution, the residual free PEG, the free sorbitol and the mono/di-ester ratio can all differ between two drums that both report HLB 16.7 and both pass the same identity test. Their solubilization capacity does not have to match. A purchase specification that reads "Polysorbate 20, HLB 16.7" therefore specifies almost nothing; add the hydroxyl and saponification windows, the 1,4-dioxane ceiling, and a sample trial on your own fragrance before the drum is accepted.
Selection quick reference
| Application | First choice | Starting ratio | Watch out for |
|---|---|---|---|
| Clear toner or body mist, citrus or conifer accord at 0.3–0.8% | Polysorbate 20 | 4:1 to 5:1 | Ratio must be set on the cold-storage result |
| Clear toner, floral or fruity accord at 0.5–1.5% | Polysorbate 20 | 3:1 | One woody base note can double the requirement |
| Leave-in hair mist carrying silicone or vitamin E | PEG-40 HCO | 3:1 to 5:1 | Cloud point 65–75 °C; check hot filling and shipping |
| Clear shampoo or shower gel at 0.3–0.5% fragrance | PEG-40 HCO or a co-formulated solubilizer blend | 3:1 to 4:1 | Surfactant base already contributes micelles; test in the real base |
| Wet-wipe lotion or electrolyte-rich system | Solubilizer blend plus salt ladder | 4:1 upward | Salting-out; measure with the preservative salt present |
| Food, oral or pharma-adjacent | Grades with an E number: E432 (PS20), E433 (PS80), E434 (PS40), E435 (PS60), E436 (PS65) | Per regulation | Polysorbate 85 has no E number and is not on the EU food additive list |
All grades discussed here are stocked for B2B supply, with COA, TDS and samples available: Polysorbate 20 (9005-64-5), Polysorbate 40 (9005-66-7), Polysorbate 60 (9005-67-8), Polysorbate 80 (9005-65-6), Polysorbate 85 (9005-70-3), PEG-40 Hydrogenated Castor Oil (61788-85-0), the ready-made solubilizer blend Cocoeth-7 (and) PPG-1-PEG-9 Lauryl Glycol Ether (and) PEG-40 Hydrogenated Castor Oil (61791-13-7; 154248-98-3; 61788-85-0), PEG-40 Stearate (9004-99-3) for the low-foam O/W case, and Sorbitan Oleate (1338-43-8) as the low-HLB partner when a blend is needed. For the blend arithmetic itself see our guide to sorbitan esters and the HLB scale; for how ester count changes the same calculation, see PEG esters by ester count; and for preserving the finished clear water, multifunctional diols covers the alternative to a classical preservative system. Sample quantities and formulation support are available through the enquiry form on any product page.