What is a natural solubiliser? A natural solubiliser is a plant-derived ingredient that allows oil-soluble substances — essential oils, fragrance compounds, and oil-based extracts — to disperse evenly and stably into water-based formulations. Without a solubiliser, oils simply float on the surface of water, creating an unstable, separated product. A solubiliser bridges the gap between the two phases, producing a clear or translucent blend without requiring emulsification equipment or synthetic surfactant systems.
There is something almost alchemical about the moment a cloudy, separated liquid becomes clear. One ingredient. A little knowledge. And suddenly what looked like a failed formula transforms into something genuinely beautiful. That is the quiet power of the natural solubiliser — and it is one of the most underestimated tools in the small-batch formulator's kit.
This article is for the formulator who wants to understand not just what this ingredient does, but how it does it, when to reach for it, and how to use it with confidence. We will also address the questions around castor oil, citric acid, and other substitutes that get suggested online — because some of that advice deserves more scrutiny than it usually gets.
What Is a Natural Solubiliser and How Does It Work?
What is a natural solubiliser? A natural solubiliser is a plant-derived ingredient that allows oil-soluble substances — essential oils, fragrance compounds, and oil-based extracts — to disperse evenly and stably into water-based formulations. Without a solubiliser, oils float on the surface of water, creating an unstable, separated product. A solubiliser bridges the gap between the two phases, producing a clear or translucent blend without emulsification equipment or synthetic surfactant systems.
The chemistry behind this involves what is called HLB — Hydrophilic-Lipophilic Balance. Every emulsifier and solubiliser sits somewhere on this scale. High HLB ingredients are water-loving; low HLB ingredients are oil-loving. A solubiliser sits at the high end of the HLB scale, meaning it is predominantly water-friendly but carries enough oil-affinity to grab onto essential oil molecules and pull them into suspension in the water phase.
The Kalós Natural Solubiliser is PEG-free and nonionic — meaning it carries no electrical charge, making it compatible with a wide range of cosmetic ingredients across different pH ranges, without the concerns associated with PEG-based solubilisers that more discerning formulators are increasingly moving away from.
Formulator's Note: A solubiliser is not an emulsifier — and this distinction matters in practice. An emulsifier creates a stable blend of two immiscible phases at significant concentrations, typically 3–6%, and requires a meaningful water phase and an oil phase. A solubiliser is designed for much lower oil-phase inputs: typically 1–5% essential oil or fragrance, solubilised into a water base. Using a solubiliser where an emulsifier is required — or vice versa — will produce an unstable formula. If your formulation has a meaningful oil phase above 5–10%, reach for an emulsifier. If you are adding a fragrance or essential oil to a mist or toner, the Natural Solubiliser is your ingredient.
What Can I Use as a Solubiliser?
What can I use as a solubiliser? The most effective and reliable solubilisers for cosmetic formulation are purpose-designed nonionic surfactants, typically derived from plant sources. Polysorbate 20 is the most widely used conventional option. PEG-free plant-derived alternatives — like the Kalós Natural Solubiliser — deliver the same performance without the synthetic concerns. Outside of these, the options narrow considerably in terms of reliability and true solubilisation performance.
You will find several substitutes suggested in online formulation communities. Here is an honest assessment of the main ones:
- Alcohol (ethanol or isopropyl alcohol): Works as a co-solvent to disperse essential oils into water-based formulas at higher concentrations, but introduces dryness and is not suitable for skin types that react to alcohol. Not a true solubiliser — it does not produce a clear, stable dispersion the way a purpose-built ingredient does, and it evaporates.
- Castor oil: See the dedicated section below — this one requires a direct answer.
- MCT oil (Capric/Caprylic Triglyceride): A carrier oil, not a solubiliser. It will not disperse essential oils into water. Useful in oil-based formulations, not in water-based ones.
- Polysorbate 80: A heavier, oilier polysorbate suitable for larger oil-phase loadings. Works well but has a greasy skin-feel at higher concentrations and is not PEG-free. A legitimate option where Polysorbate 20 under-performs.
The bottom line: for clean, stable, clear water-based products with essential oils or fragrances, a purpose-designed PEG-free solubiliser is the most reliable tool available. Substitutes work in some contexts but each carries trade-offs that affect stability, skin-feel, or formulation integrity.
What Are Examples of Solubilisers?
What are examples of solubilisers in cosmetic formulation? The most common solubilisers used in cosmetics include Polysorbate 20 (the conventional standard), PEG-40 Hydrogenated Castor Oil (for oil-heavy formulations), Caprylyl/Capryl Glucoside (mild, natural-positioned), and PEG-free nonionic alternatives derived from plant fatty acids and sugars. Each has a different HLB value, oil-loading capacity, and skin-feel profile.
Here is a practical comparison of the most relevant options:
- Polysorbate 20: High HLB (~17), excellent for light essential oil loadings in water up to approximately 5%, very low viscosity, slightly astringent skin-feel. The industry standard. Contains PEG.
- PEG-40 Hydrogenated Castor Oil: Lower HLB than Polysorbate 20, handles heavier oil loadings, slightly oilier skin-feel, good for fragrances with larger molecules. Contains PEG.
- Caprylyl/Capryl Glucoside: Mild, sugar-derived, suitable for sensitive skin formulations. Lower solubilisation capacity — requires more product for the same effect. PEG-free.
- Kalós Natural Solubiliser: PEG-free, nonionic, plant-derived. High solubilisation performance across a range of essential oils and fragrances. Clear product in water at recommended usage rates. Designed for the small-batch formulator who wants performance without synthetic compromise.
The ingredient you choose should match your formula's oil loading, your product's pH, and your brand positioning. If you are formulating for a clean, natural-positioned range, PEG-free is the appropriate choice. Browse the full solubilisers range to compare available options.
Formulator's Note: The ratio of solubiliser to essential oil matters more than most beginners realise. A starting ratio of 3:1 to 4:1 (solubiliser to essential oil by weight) is typical for the Kalós Natural Solubiliser — meaning for every 1% essential oil in your formula, you need approximately 3–4% solubiliser. This ratio varies depending on the specific oil — heavier, more resinous oils require more solubiliser than light citrus oils. Always test before scaling. Pre-dissolve the essential oil in the solubiliser first, then add the combined mixture to your water phase slowly while stirring.
Is Castor Oil a Solubiliser?
Is castor oil a solubiliser? Not in the conventional cosmetic sense. Refined castor oil has unusually high polarity for a carrier oil due to its ricinoleic acid content, which gives it greater miscibility with alcohols and some polar solvents than most fixed oils. This has led to its use as a co-solvent in specific anhydrous formulations — lipsticks, lip glosses, and some hair oils — where its polarity helps blend pigments or fragrances into oil-only systems. However, castor oil cannot disperse oil-soluble ingredients into a water phase. It has no meaningful water-dispersing capability.
Where castor oil is sometimes used as a functional solubilising agent is in PEG-40 Hydrogenated Castor Oil — an ethoxylated derivative of castor oil that has genuine HLB solubilising properties. This is a chemically modified ingredient, not the raw refined oil itself. The name causes significant confusion in formulation communities.
If you are working with refined castor oil in your formulations, it is best understood as a conditioning carrier oil with a distinctive texture and high viscosity — an excellent ingredient in its own right, but not a substitute for a purpose-built solubiliser in water-based products.
Formulator's Note: Castor oil is genuinely useful in oil-cleansing formulations, hair treatments, and anhydrous balms — its polarity makes it a natural binder for pigments in lip products and an excellent thickener in cleansing oils. For a full comparison of castor oil variants and their formulation uses, see our article on cold-pressed vs Jamaican Black Castor Oil. Just do not ask it to do a solubiliser's job in a water-based formula — that is not where it belongs.
Is Citric Acid a Solubiliser?
Is citric acid a solubiliser? No. Citric acid is a pH adjuster and chelating agent — used in cosmetic formulations to lower pH, improve preservation efficacy, and chelate metal ions that can destabilise formulations. It has no ability to disperse oil-soluble ingredients into water. Its name sometimes creates confusion, but pH adjustment and solubilisation are entirely different chemical functions performed by entirely different classes of ingredient.
What citric acid does do is make your preservatives work harder. Many preservation systems, including broad-spectrum options like Saliguard BDHA, function most effectively at a specific pH range. Citric acid is your tool for bringing the formula to that range — and maintaining it over the product's shelf life. In that role, it is indispensable. In a solubilising role, it is irrelevant.
If you are finding suggestions online to use citric acid as a solubiliser, they are incorrect. The two ingredients solve entirely different formulation challenges, and conflating them will produce unstable, poorly preserved products.
Where the Natural Solubiliser Truly Earns Its Place
This is the ingredient that unlocks some of the most elegant product types in the small-batch formulator's range. Here is where it makes the most meaningful difference:
- Facial and body mists: The classic application. A floral water or hydrosol base with essential oil — without a solubiliser, those oils float, separate, and can cause skin irritation or staining. With a solubiliser, the product is crystal clear, stable, and evenly distributed every time the bottle is sprayed.
- Room and linen sprays: Same principle applied off-skin. Fragrance compounds in a water base require a solubiliser for stability, clarity, and consistent scent throw.
- Shower gels and shampoos with essential oils: Adding essential oils to a surfactant base without a solubiliser produces cloudiness, inconsistent scent, and potential stability issues. A solubiliser ensures even distribution. Note that in high-surfactant bases — like those built on Sodium Cocoyl Isethionate or Cocoamidopropyl Betaine — the surfactants themselves provide some solubilising capacity, but a dedicated solubiliser still improves clarity and scent stability.
- Toners and essences: Botanical extracts and fragrance components in toner bases benefit from proper solubilisation, particularly where the product is expected to be clear and sophisticated in appearance.
- After-sun and gel formulations: Water-dominant products that incorporate oil-soluble actives or fragrance — the solubiliser ensures even distribution of those ingredients through the gel matrix.
Formulator's Note: The Kalós Natural Solubiliser is also compatible with D-Limonene — a citrus-derived fragrance ingredient and natural cleansing agent. D-Limonene is notoriously difficult to incorporate into water-based formulas without a high-performance solubiliser due to its low polarity and volatility. If you are formulating a citrus-forward mist, cleanser, or room spray using D-Limonene alongside Tea Tree Essential Oil or other essential oils from our range, test your solubiliser ratio carefully before scaling — citrus terpenes typically require a slightly higher solubiliser-to-oil ratio than other essential oils.
The Formulator's Quick Reference
For those building with this ingredient:
- Usage rate: 3–10% in finished formulations, depending on essential oil or fragrance loading
- Solubiliser-to-essential oil ratio: Start at 3:1 to 4:1 (solubiliser:EO by weight) and adjust through testing
- Phase: Water phase — pre-dissolve the essential oil in the solubiliser first, then add to water
- Heat: Not required — cold-process compatible
- pH range: Effective across a broad pH range — always verify against your finished formula
- Appearance indicator: Produces clear to slightly translucent dispersions at correct usage rates — cloudiness indicates insufficient solubiliser for the oil loading
- Compatibility: Compatible with hydrosols, floral waters, aloe vera gel, and most water-phase ingredients; works alongside humectants without issue
- Preservation: Water-containing formulas incorporating a solubiliser require a full preservation system — do not rely on the essential oil to preserve the water phase
- PEG-free status: Yes — appropriate for natural-positioned and clean beauty formulations
Browse the full solubilisers range for all available options.
Frequently Asked Questions
What is a natural solubiliser?
A natural solubiliser is a plant-derived ingredient that allows oil-soluble substances such as essential oils and fragrance compounds to disperse stably and evenly into water-based formulations. It bridges the chemical incompatibility between oil and water, producing a clear or translucent product without requiring a full emulsification system.
What can I use as a solubiliser?
The most reliable options are purpose-designed nonionic solubilisers such as Polysorbate 20 or PEG-free plant-derived alternatives. Alcohol can work as a co-solvent in some formulations but is not a true solubiliser. Castor oil and MCT oil cannot disperse oils into a water phase and are not substitutes for a dedicated solubiliser.
What are examples of solubilisers in cosmetics?
Common examples include Polysorbate 20, PEG-40 Hydrogenated Castor Oil, Caprylyl/Capryl Glucoside, and PEG-free plant-derived nonionic alternatives. Each has different HLB values, oil-loading capacity, and skin-feel profiles. The right choice depends on your formula's oil phase content, pH, and brand positioning.
Is castor oil a solubiliser?
Refined castor oil is not a solubiliser for water-based formulations. Its high polarity makes it useful as a co-solvent in anhydrous systems like lip products, but it cannot disperse oils into water. PEG-40 Hydrogenated Castor Oil is a chemically modified derivative with genuine solubilising properties — it is a different ingredient despite the similar name.
Is citric acid a solubiliser?
No. Citric acid is a pH adjuster and chelating agent used to lower pH and support preservation efficacy in cosmetic formulations. It has no solubilising capability and cannot disperse oil-soluble ingredients into water. pH adjustment and solubilisation are entirely different chemical functions.
The Clarity Your Formulations Deserve
There is a particular satisfaction in watching a formula come together correctly — that moment when a cloudy, separated mixture becomes clear and unified. The natural solubiliser makes that moment possible in some of the most beautiful product types a small-batch formulator can create: crystal-clear facial mists, elegantly scented toners, stable room sprays that carry their fragrance evenly to the last drop.
It is not a complicated ingredient. It just needs to be understood — and used at the right ratio, in the right application, for the right product type.
The Kalós Natural Solubiliser is PEG-free, plant-derived, and ready for your water phase. Browse the full solubilisers range or explore our essential oils and fragrances to find the ingredients that belong in your next formula.
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