The Dual-Phase Formulation Design of "Eye and Lip Makeup Removers": Water-Oil Separation Ratios and Emulsification Logic
Updated: Sep 17
I. Why Do Eye and Lip Makeup Removers Need a Dedicated Product?
Open a bottle of dedicated eye and lip makeup remover, give it a gentle shake, and watch the blue upper layer and the clear lower layer merge back together. This shaking motion is not just a visual ritual designed by the brand; it is a necessary usage step backed by rigorous formulation science.
Eye and lip makeup is the most challenging part of the face to remove. The formulation structure of waterproof mascara dictates its naturally high removal difficulty. Unlike the oil-in-water system of ordinary mascaras, waterproof formulas contain 70%–85% oil phase. This lipophilic continuous outer phase (where ingredients like Isododecane account for 30%–50% of the oil phase) forms a physicochemical barrier that locks the mascara onto the eyelashes.
In 2025, waterproof mascara formulations have been further upgraded. Traditional formulas used 45%–55% waxes, but mainstream 2025 formulations have reduced waxes to 30%–40%, instead introducing 25%–35% high-performance polymers (such as acrylates copolymers). This forms an ultra-low energy film with a surface tension of approximately 22.72 mJ/m², causing water and oil to bounce off the lashes rather than penetrate the pigment layer.
Lipsticks and long-lasting lip glosses are the same: hard waxes (including carnauba wax, candelilla wax, beeswax) crystallize to form a film, creating a water- and oil-repellent physical barrier on the lips. The solubility category of film-forming agents is one of the most important criteria when selecting makeup removal ingredients.
The core chemical principle for removing such makeup is just one rule: "Like dissolves like." Oil-based impurities (including waxes, silicones, and pigments) can only be properly broken down by oil-based products. Foaming cleansers or ordinary micellar water without an oil phase will merely move the makeup around on the skin rather than truly dissolving it, forcing consumers to rub forcefully and thereby irritating the skin.
This is the exact value proposition of bi-phase (biphasic) makeup removers—it synergizes the high-efficiency dissolution power of the oil phase with the refreshing wash-off feel of the water phase in a single product, specifically designed for the highly challenging removal scenarios of eye and lip makeup.
II. The Physicochemical Basis of Bi-Phase Makeup Removers: Why Must the Two Phases Separate?
The visual characteristic of a bi-phase makeup remover—clearly separated into two layers at rest, briefly mixed when shaken—is not a coincidence, but a carefully designed thermodynamic state by formulation engineers.
The Thermodynamic Driving Force of Water-Oil Separation
There is a significant density difference between the oil phase (density approx. 0.8–0.9 g/cm³) and the water phase (density approx. 1.0–1.1 g/cm³), and the polarity difference between the two phases is massive. Without the intervention of sufficient emulsifiers, the thermodynamic stable state of the oil and water phases is Phase Separation, not a homogeneous mixture.
This is the fundamental reason why bi-phase formulas opt for an "incomplete emulsification" design:
If enough emulsifier is added to form a stable emulsion (O/W or W/O), the product becomes an emulsion-type makeup remover, losing the bi-phase visual appearance.
The bi-phase formula adds only a very small amount of low-efficiency emulsifier or none at all, allowing the two phases to form a Transient Microemulsion when shaken—just enough to exert a synergistic cleansing effect during the brief time the cotton pad touches the skin, and then naturally re-separates.
The sensory value of this design is: the oil phase dissolves the makeup, and the water phase washes away the oil phase loaded with makeup, leaving the skin without a heavy, oily residue feel.
III. The Water-Oil Ratio of Bi-Phase Makeup Removers: Scientific Basis for the Design Window
For brand owners, "what proportion should the water and oil phases each take" is one of the most core formulation decisions when developing a bi-phase makeup remover.
Through systematic analysis of mainstream brand formulations on the market, the following ratio patterns can be summarized:
Reference Range for Water-Oil Ratios in Mainstream Market Formulations
Taking Lancôme Bi-Facil bi-phase eye makeup remover as an example, its ingredient list is arranged as: Water (Aqua), Cyclopentasiloxane, Isohexadecane, Sodium Chloride... Both water and oil phase ingredients are at the forefront of the list, with the oil phase accounting for about 30%–45% of the overall formula.
Germaine de Capuccini's improved bi-phase formula uses Isohexadecane and Caprylic/Capric Triglyceride to form the oil phase. When shaken, it forms a microemulsion capable of removing waterproof and long-lasting makeup in a single wipe, without friction and without greasy residue.
Comprehensive market analysis shows that the water-oil ratio of bi-phase
makeup removers usually falls into the following ranges:
Formulation Direction | Oil Phase Ratio | Water Phase Ratio | Applicable Scenarios |
Strong Waterproof Makeup Type | 40%–50% | 50%–60% | Long-lasting waterproof mascara, transfer-proof lip color |
Balanced Daily Type | 30%–40% | 60%–70% | Daily eye makeup + lip color combination removal |
Refreshing Type (Water-Biased) | 20%–30% | 70%–80% | Daily light makeup, consumers preferring a non-greasy feel |
If the oil phase is too low (<20%): The oil phase is insufficient to fully dissolve waterproof film-forming agents, requiring repeated wiping and irritating the sensitive periorbital skin.
If the oil phase is too high (>55%): The temporary emulsification effect after shaking is poor, the oil phase separates back too quickly, resulting in a poor user experience; the skin feels noticeably greasy after cleansing.
IV. Oil Phase Ingredient Selection: Which Oils Are Best for Bi-Phase Makeup Removers?
The selection of oil phase ingredients must simultaneously meet three conditions: high efficiency in dissolving waterproof makeup, low irritation to the eye mucosa, and no heavy greasy feel after cleansing. Under these three constraints, the following ingredients are the mainstream choices in the industry:
Volatile Silicones: Cyclopentasiloxane (D5)
This is currently the core oil phase ingredient with the highest market share in bi-phase makeup removers. Cyclopentasiloxane provides a lightweight feel with fast evaporation, making the skin feel clean and non-greasy after cleansing. Its core advantages are: fast evaporation speed (boiling point approx. 211°C, but evaporates significantly at skin temperature), high efficiency in dissolving silicone-based film-forming polymers (the core components of waterproof makeup), and a lightweight, residue-free feel upon skin contact. Formulation Note: EU Regulation 2023/2055 has restricted the use of cyclic siloxanes D4, D5, and D6 in rinse-off cosmetics; brand owners must check the latest regulatory limits and consider alternatives (such as C13-15 Alkane, Isododecane, etc.).
Light Hydrocarbons: Isohexadecane
Isohexadecane ranks at the forefront of the ingredient lists in multiple mainstream bi-phase makeup remover brands, synergizing with cyclopentasiloxane to form the oil phase skeleton for highly efficient makeup dissolution. Isohexadecane is a branched alkane with a high boiling point but excellent skin spreadability. It has outstanding dissolution efficiency for waxes (mascara waxes) and non-polar film-forming polymers, with good eye tolerance.
Natural Source Light Oils: Jojoba Oil / Caprylic/Capric Triglyceride (CCT)
For bi-phase makeup removers positioned for Clean Beauty or organic certification, natural source light oils are used to replace volatile silicones and hydrocarbons: Jojoba Oil (structurally similar to skin sebum) helps dissolve and remove heavy makeup while balancing sebum rhythm for oily skin consumers. Caprylic/Capric Triglyceride (CCT), derived from coconut oil, is lightweight and fast-absorbing, with good dissolving power for oil-soluble makeup components and skin-refatting effects.
V. Water Phase Design: Skincare Value Beyond Cleansing
The water phase of a bi-phase makeup remover is not just a "filler"; it is an active platform that achieves the following three functions:
1. Carrying Micelle Formers — Completing the Cleansing of Water-Soluble Makeup
Poloxamer 184 dissolved in the water phase (the core surfactant in ordinary micellar water) is responsible for forming micelles to encapsulate water-soluble pigments, eyeshadow powders, and water-soluble film-forming polymers, making up for the oil phase's shortfall in dissolving hydrophilic makeup components. This is the key advantage of bi-phase makeup removers over purely oily removers: the oil phase solves lipophilic makeup, and the water phase solves hydrophilic makeup. The two phases synergize to cover the complete ingredient spectrum of waterproof makeup formulations.
2. Carrying Periorbital Soothing and Moisturizing Ingredients
Panthenol can enhance hydration and reduce TEWL in bi-phase makeup removers, improving skin texture and appearance. The following efficacy ingredients can be simultaneously introduced into the water phase:
Glycerin: 3%–5%, basic hydration, reducing post-cleansing tightness.
Panthenol: 0.5%–1%, hydration + skin repair.
Allantoin: 0.1%–0.2%, soothing mild periorbital irritation.
Cucumber Extract: Cooling and soothing, suitable for the eye area.
3. Controlling the Two-Phase Separation Speed via Electrolytes
Sodium Chloride (NaCl) is an indispensable functional ingredient in the water phase of bi-phase makeup removers, and its role transcends the cognition of most brand owners: The presence of salt ions increases the interfacial tension difference between the water and oil phases—it increases the ionic strength of the water phase, further reducing the tendency of the oil and water phases to dissolve into each other. This allows the product to re-separate at a reasonable speed (usually within 30–60 seconds) after shaking stops. This speed ensures that the two phases remain in a mixed, activated state before the consumer finishes wiping, without causing the separation to be too slow (which would affect the product's clear appearance). Common usage of Sodium Chloride in bi-phase makeup removers: 0.3%–2.0%; the separation speed can be fine-tuned by adjusting the concentration.
VI. Emulsification Logic: Precise Control of "Incomplete Emulsification" in Bi-Phase Makeup Removers
This is the most subtle and testing part of bi-phase makeup remover formulation engineering.
The Physical Basis of the Shaking Activation Mechanism
In a static state, the oil and water phases naturally separate according to the density difference. When shaken vigorously, mechanical energy is injected, breaking the interface between the two phases and forming a Transient Microemulsion—oil phase micro-droplets (diameter approx. 1–10 µm) are temporarily dispersed in the water phase. At this point, the cotton pad touches the skin, the oil phase micro-droplets contact and dissolve the makeup components, and the water phase simultaneously cleanses the hydrophilic components. After shaking stops, this non-equilibrium microemulsion naturally breaks down within tens of seconds to a few minutes, and the oil and water phases re-separate—requiring no manual intervention.
Precise Control of Emulsifier Dosage: 0 is Not Enough, Too Much Becomes a Stable Emulsion
The selection of emulsifiers in bi-phase makeup removers follows a counter-intuitive principle: the lower the emulsifier dosage, the better, but it cannot be zero.
Completely free of emulsifiers: The two phases re-separate within seconds after shaking. The consumer has fully separated phases before finishing the cotton pad wipe, and the two phases cannot exert a synergistic effect.
Excessive emulsifier (exceeding the HLB balance requirement): The two phases form a stable emulsion, losing the bi-phase appearance and losing the product's positioning.
Optimal emulsifier dosage: Keeps the two phases in a mixed, activated state for 30–90 seconds after shaking, then slowly re-separates.
Poloxamer 184 (Polyoxyethylene-polyoxypropylene block copolymer) is one of the ideal emulsifiers to achieve this precise control: its low CMC (Critical Micelle Concentration) allows it to form effective micelles at extremely low concentrations (0.5%–1%). Meanwhile, due to its unique temperature sensitivity (slightly thickens at body temperature), it can maintain a brief two-phase mixed state upon skin contact, and then re-separates at room temperature.
VII. Analysis of Mainstream Market Formulations: Reading the Design Logic from the Ingredient List
Below is a structural analysis of three representative commercially available bi-phase makeup remover formulations:
Formula A: Lancôme Bi-Facil (Silicone-Oil Dominant Classic Formula)
Ingredients: Aqua, Cyclopentasiloxane, Isohexadecane, Sodium Chloride, Poloxamer 184, Benzyl Alcohol, Benzalkonium Chloride...
Formulation Logic:
Oil phase skeleton: D5 (Cyclopentasiloxane) + Isohexadecane, powerfully dissolving waterproof components.
Emulsification/Micelle: Poloxamer 184 at an extremely low amount (0.5%–1%), only achieving transient mixing when shaken.
Water phase electrolyte: Sodium Chloride controls the separation speed.
Formulation Shortcoming: Contains Benzalkonium Chloride (BAK), a known corneal toxic ingredient. Sensitive eyes and contact lens wearers should be cautious (this ingredient is a major target for formulation improvement).
Formula B: GrandeVANISH (Plant Extract / Clear Beauty Formula)
Ingredients: Water, Cyclopentasiloxane, Isoeicosane, C13-15 Alkane, Cucumber Extract, Isohexadecane, Simmondsia Chinensis Seed Oil, Hexapeptide-11...
Formulation Logic:
Oil phase upgrade: Introduces C13-15 Alkane (bio-based alkane, replacing some petroleum-derived ingredients) + Jojoba Oil.
Efficacy actives: Hexapeptide-11, seaweed extract series, positioning the makeup remover as an "eye-protecting functional product."
Preservation system: Ethylhexylglycerin + Phenoxyethanol low-irritation compound, replacing Benzalkonium Chloride.
Formula C: Silicone-Free Natural Organic Formula
Ingredients: Aqua (Water), Isohexadecane, Caprylic/Capric Triglyceride, Pentylene Glycol, Sodium Chloride, Avena Sativa (Oat) Kernel Extract, Tocopherol...
Formulation Logic:
Completely silicone-free: Replaces cyclopentasiloxane with Isohexadecane + Caprylic/Capric Triglyceride.
Natural actives: Oat extract (skin soothing), beta-carotene (antioxidant), Vitamin E (Tocopherol).
No chemical emulsifiers: Shaking forms pure physical micro-dispersion, separation speed is faster (approx. 15–30 seconds).
VIII. Packaging Design Logic for Bi-Phase Makeup Removers: Container Selection is an Extension of the Formulation
The packaging choice for bi-phase makeup removers is not a purely aesthetic decision, but a technical decision directly related to formulation stability:
Transparent Bottles (PET/Glass): Consumers can intuitively see the dual-layer separation effect, making it the most common choice; transparent bottles are also the core carrier for product visual differentiation (e.g., coloring the upper layer: like Lancôme's clear blue oil phase).
Cap Design: Must have reliable sealing to prevent oil phase leakage; at the same time, it must ensure that the shaking motion can effectively mix the two phases thoroughly (the bottle neck should not be too narrow).
Avoid Pumps: Pump designs are inconvenient for the shaking activation action required before each use of a bi-phase product, and it is also difficult to guarantee the simultaneous output of the oil and water phases.
UV Protection: Formulations containing natural oils (Jojoba Oil, plant extracts) must consider light-blocking packaging to prevent photo-oxidation.
Conclusion: Bi-Phase Is Not Just a Product Form, but a Formulation Philosophy
Every design detail of a bi-phase eye and lip makeup remover—the selection of oil phase ingredients, the determination of the water-oil ratio, the micro-control of emulsifiers, the fine-tuning of electrolyte concentrations, the alignment of pH and periorbital physiological parameters—all point to the same goal: achieving the highest efficiency in dissolving waterproof makeup while exerting the lowest irritation burden on the skin and mucous membranes of the eye and lip areas.
This delicate balance is the core of why bi-phase makeup removers maintain their unique value in the fiercely competitive makeup remover category, and it is also a key dimension of formulation capability that brand owners should focus on when selecting an OEM/ODM partner factory.
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