If you have ever tried to mix oil and water together, you already understand the fundamental problem that emulsifiers solve. Shake them in a bottle and they will briefly combine — but within seconds, the two phases separate again, the oil floating to the top and the water sinking below. This is simply physics: oil and water are immiscible, meaning their molecular structures do not allow them to mix stably on their own.
Yet the most beloved skincare products in the world — moisturisers, day creams, body lotions, SPF formulations — are all emulsions. They are stable, homogeneous mixtures of oil and water that stay combined for months or years without separating. The ingredient that makes this possible is the emulsifier.
Understanding how emulsifiers work is one of the most important milestones in a DIY formulator's education. It is the point at which you move from making simple anhydrous (oil-only) products like face oils and body butters, to creating the full range of water-based and emulsified skincare. This guide explains the science clearly, walks you through the most commonly used emulsifier types, and gives you a complete beginner lotion recipe to start with.
If you are not yet ready to formulate from scratch, The Skin Science Company's Rich Cream Base is a professionally formulated, pre-emulsified base that you can customise with your own active ingredients, oils, and fragrances — a great starting point before you begin building emulsions from the ground up.
How Emulsifiers Work: The Science Made Simple
An emulsifier is a molecule with a split personality. One end of the molecule is hydrophilic (water-loving) and the other is lipophilic (oil-loving). When an emulsifier is present in a mixture of oil and water, its molecules arrange themselves at the interface between the two phases — the lipophilic end pointing into the oil droplets, and the hydrophilic end pointing outward into the water. This creates a stable barrier around each oil droplet, preventing them from coalescing and separating back out.
The result is an emulsion: a dispersion of tiny oil droplets suspended throughout a continuous water phase (or, less commonly, water droplets in a continuous oil phase). The stability of the emulsion depends on the type and concentration of emulsifier used, the ratio of oil to water, the processing technique, and the presence of co-emulsifiers and thickeners.
A note on HLB (Hydrophilic-Lipophilic Balance): Every emulsifier has an HLB value — a number from 1 to 20 that describes how hydrophilic or lipophilic it is. Emulsifiers with a low HLB (1–6) are better suited to water-in-oil emulsions (richer, more occlusive creams). Emulsifiers with a high HLB (8–18) are better suited to oil-in-water emulsions (lighter lotions and creams). Most DIY-friendly emulsifiers are designed to work within the oil-in-water range, which is the most common type in skincare.
The Most Common Emulsifier Types for DIY Skincare
Emulsifying Wax NF (E-Wax)
Emulsifying wax NF is one of the most widely used emulsifiers in DIY skincare, particularly for beginners, because it is straightforward to use and produces stable, creamy emulsions with a wide range of oil-to-water ratios. It is a blend of cetearyl alcohol and polysorbate 60 (or similar surfactants), and it functions as a complete emulsifier on its own — meaning you do not need to combine it with a co-emulsifier to achieve stability.
Typical usage rate: 3–8% of total formulation weight, depending on the oil content.
Cetearyl Alcohol + Glyceryl Stearate (Self-Emulsifying)
This is the emulsifier combination used in SSC's own Rich Cream Base. Cetearyl alcohol is a fatty alcohol that acts as both a co-emulsifier and a thickener, giving lotions and creams a smooth, stable texture. Glyceryl stearate SE (self-emulsifying) is a glycerol ester of stearic acid that provides emulsification and a pleasant, non-greasy skin feel. Together, these two ingredients are a classic and reliable combination used in professional cosmetic manufacturing.
Typical usage rate: Cetearyl alcohol at 2–5%, glyceryl stearate SE at 1–3%.
BTMS-50 (Behentrimonium Methosulfate and Cetyl Alcohol)
BTMS-50 is a cationic (positively charged) emulsifier that is particularly popular in hair care formulations — conditioners, hair masks, and leave-in treatments — because its positive charge helps it adhere to the negatively charged surface of hair strands. It produces rich, creamy emulsions with excellent conditioning properties. It can also be used in skin care, though it is less common there than in hair care.
Typical usage rate: 4–8%.
Olivem 1000 (Cetearyl Olivate and Sorbitan Olivate)
Olivem 1000 is a natural, olive-derived emulsifier that is popular in natural and organic formulations. It produces emulsions with a distinctive, lightweight, silky skin feel and is compatible with a wide range of active ingredients. It is somewhat more sensitive to formulation conditions (particularly pH and electrolytes) than synthetic emulsifiers, so it requires a little more care.
Typical usage rate: 3–6%.
Lecithin
Lecithin is a naturally occurring phospholipid found in soy, sunflower, and egg yolk. It is a gentle, skin-compatible emulsifier that is particularly valued in natural formulations. It produces softer, less stable emulsions than the above options and is often used as a co-emulsifier alongside a primary emulsifier rather than as a standalone.
Liquid vs Solid Emulsifiers: Which One Do You Need?
If you are new to formulating, the difference between liquid and solid emulsifiers can be confusing. Both help oil and water work together, but they are used in different products and at different levels.
Solid emulsifiers, often sold as waxes, flakes or pellets, are the backbone of creams and lotions. They are melted into the heated oil phase, then combined with the heated water phase and mixed until the emulsion forms and thickens as it cools. They usually make up about 3 to 8% of a cream or lotion, and many also add body and a smooth, cushioned feel.
Liquid emulsifiers and solubilisers. Many liquid ingredients sold for "mixing oil into water" are solubilisers rather than cream emulsifiers. They disperse a small amount of oil, such as essential oil or fragrance, into a water-based product so it stays clear. They suit mists, toners, room sprays and gels, and are usually used at a few times the amount of oil you want to disperse. Some liquid emulsifiers can also build lotions, but they are less common in beginner formulas.
Which one do I need?
Making a cream or lotion: a solid emulsifier.
Adding essential oil to a toner, mist or gel: a solubiliser.
Any water-based product: a broad-spectrum preservative as well.
To learn more, our Guide to Emulsifiers in Cosmetic Formulation covers oil-in-water and water-in-oil emulsions and how to make stable lotions and creams.
Key Supporting Ingredients
Emulsifiers rarely work alone. A well-formulated lotion or cream typically includes several supporting ingredients that contribute to stability, texture, and skin feel.
Co-emulsifiers and thickeners such as cetyl alcohol and stearic acid are fatty alcohols and acids that work alongside the primary emulsifier to stabilise the emulsion and adjust its viscosity. Stearic acid, for example, is listed in the SSC Rich Cream Base ingredients and contributes to the cream's firm, stable texture.
Humectants such as glycerin draw moisture from the environment into the skin and help keep the water phase of the emulsion stable. Glycerin is one of the most effective and well-tolerated humectants available, and it is a standard inclusion in almost every professional lotion and cream formulation. A typical usage rate is 2–5%.
Preservatives are essential in any formulation containing water. Water-based products are susceptible to microbial contamination — bacteria, mould, and yeast can all grow in an unpreserved lotion within days. Phenoxyethanol (used in SSC's own cream base) is one of the most widely used cosmetic preservatives, effective at 0.5–1% and well-tolerated by most skin types.
Antioxidants such as Vitamin E Oil protect the oil phase from oxidation and extend shelf life. Usage rate: 0.5–1%.
Formulation Principles: Oil-to-Water Ratios
The ratio of oil phase to water phase is one of the most important decisions in lotion formulation. It determines the product's richness, absorption speed, and overall skin feel.
| Product Type | Water Phase % | Oil Phase % | Skin Feel | Best For |
|---|---|---|---|---|
| Lightweight body lotion | 75–80% | 15–20% | Light, fast-absorbing | Normal to oily skin, summer |
| Standard face/body cream | 65–75% | 20–30% | Medium, balanced | Normal to dry skin, year-round |
| Rich face or night cream | 55–65% | 30–40% | Rich, nourishing | Dry, mature skin, winter |
| Very rich body butter cream | 40–55% | 40–55% | Very rich, slow-absorbing | Very dry, cracked skin |
How Much Emulsifier Do You Need?
A useful starting point is an emulsifier level of about 25 to 30% of your total oil phase. A formula with a 15% oil phase would start at roughly 3.75 to 4.5% emulsifier. Treat this as a starting point, not a fixed rule, and confirm the final level through stability testing.
Watch your electrolytes. Salt- and acid-heavy actives, such as niacinamide at higher levels, vitamin C and AHAs, can disrupt the emulsifier network and make a lotion thin out or separate. If you are using them, choose an emulsifier your supplier lists as electrolyte tolerant (glucoside-based Montanov 68, INCI Cetearyl Alcohol, Cetearyl Glucoside, is a common choice) and test early.
Combining emulsifiers. Two compatible oil-in-water emulsifiers can be used together to fine-tune stability and skin feel. Keep the combined total in line with the oil phase guide above.
Processing Olivem 1000. Olivem 1000 builds a liquid crystalline (lamellar) structure: layers of oil and water arranged much like the skin's own lipids. To form it, emulsify above about 70 to 75°C, then cool slowly with gentle stirring. Fast cooling or very high shear breaks the structure up and can leave you with an unstable emulsion.
A Beginner Lotion Recipe: Simple Autumn Body Lotion
This recipe produces a standard, balanced body lotion — approximately 100 g — using ingredients available from The Skin Science Company. It is designed to be achievable for a first-time emulsion maker, using a reliable emulsifier system and straightforward method.
| Phase | Ingredient | Percentage | Weight (100 g batch) | Function |
|---|---|---|---|---|
| Water Phase | Distilled Water | 68% | 68 g | Water phase base |
| Water Phase | Glycerin | 3% | 3 g | Humectant, moisture retention |
| Water Phase | Aloe Vera Gel | 5% | 5 g | Soothing, skin conditioning |
| Oil Phase | Emulsifying Wax NF | 5% | 5 g | Primary emulsifier |
| Oil Phase | Cetyl Alcohol | 2% | 2 g | Co-emulsifier, thickener |
| Oil Phase | Sweet Almond Oil | 8% | 8 g | Nourishing carrier oil |
| Oil Phase | Jojoba Oil | 5% | 5 g | Lightweight carrier, sebum-balancing |
| Oil Phase | Shea Butter | 2% | 2 g | Richness, barrier support |
| Cool-Down Phase | Rosehip Oil | 1% | 1 g | Antioxidant-rich, heat-sensitive |
| Cool-Down Phase | Vitamin E Oil | 0.5% | 0.5 g | Antioxidant, shelf-life extension |
| Cool-Down Phase | Preservative (e.g. Phenoxyethanol ) | 0.5% | 0.5 g | Broad-spectrum preservation |
| Total | 100% | 100 g |
Step-by-Step Method
Equipment needed: Digital scale (0.1 g accuracy), two heat-safe glass beakers, a double boiler or microwave, a stick blender or hand mixer, a thermometer, a 100 ml pump bottle or jar, and 70% isopropyl alcohol for sanitising.
Step 1 — Sanitise everything. Wipe all equipment and containers with 70% isopropyl alcohol. Allow to air dry completely.
Step 2 — Prepare the water phase. Weigh distilled water, glycerin, and aloe vera gel into one beaker. Heat gently to approximately 70–75°C.
Step 3 — Prepare the oil phase. Weigh emulsifying wax, cetyl alcohol, sweet almond oil, jojoba oil, and shea butter into a second beaker. Heat gently to approximately 70–75°C, stirring until the wax and butter are fully melted.
Step 4 — Combine the phases. With both phases at the same temperature (70–75°C), slowly pour the water phase into the oil phase while mixing continuously with a stick blender. Blend for 2–3 minutes until the mixture turns white and begins to thicken.
Step 5 — Cool down. Continue mixing (or stir occasionally) while the emulsion cools. Once the temperature drops below 40°C, add the cool-down phase ingredients: rosehip oil, vitamin E oil, and preservative. Stir well to incorporate.
Step 6 — Transfer and label. Pour or scoop into your sanitised container. Label with batch date and full ingredient list. Allow to cool completely before sealing.
Shelf life: Use a broad-spectrum preservative at the supplier's recommended rate, make small batches, and store in a cool, dark place. Always use clean hands or a spatula to dispense — never dip fingers directly into a jar.
How to Test Your Emulsion's Stability
A freshly made emulsion almost always looks stable. The real test is the next 24 to 72 hours, as it settles to room temperature and the emulsifier network fully sets, so do not judge a batch on day one.
Check samples at 24 hours, 48 hours and 7 days at room temperature, and keep parallel samples at 40°C and 4°C. Look for separation, oil weeping at the surface, graininess, thinning, and changes in colour or smell. An emulsion that separates at 40°C within 24 hours will not survive an Australian summer on a retail shelf.
A clean 7-day result is an early screen, not a shelf life. Products made for sale need longer stability testing and preservative efficacy (challenge) testing before you set an expiry date.
Common Emulsion Problems and How to Fix Them
| Problem | Likely Cause | Solution |
|---|---|---|
| Emulsion separates after cooling | Insufficient emulsifier, temperature mismatch between phases, or inadequate mixing | Increase emulsifier to 6–8%; ensure both phases are at the same temperature (70–75°C) before combining; blend for longer |
| Lotion is too thin / watery | Oil phase percentage too low, or insufficient thickener | Increase cetyl alcohol to 3–4%, or add a small amount of xanthan gum (0.3–0.5%) to the water phase |
| Lotion is too thick / heavy | Oil phase percentage too high, or too much thickener | Reduce cetyl alcohol or shea butter; increase water phase percentage |
| Grainy or lumpy texture | Shea butter or cetyl alcohol not fully melted before combining, or cooling too quickly | Ensure oil phase is fully liquid at 70–75°C before combining; cool slowly at room temperature |
| Emulsion smells off after a few weeks | Insufficient or no preservative; contamination during manufacturing | Always include a broad-spectrum preservative at the manufacturer's recommended rate; sanitise all equipment thoroughly |
Not Ready to Formulate from Scratch?
If this guide has introduced you to emulsion formulation but you are not yet ready to source individual emulsifiers and build from scratch, The Skin Science Company's Rich Cream Base gives you a professionally formulated, pre-emulsified starting point. It already contains cetearyl alcohol, glyceryl stearate SE, stearic acid, and phenoxyethanol the same ingredients covered in this guide so you can focus on customising with your chosen carrier oils, actives, and fragrances without worrying about emulsion stability.
Browse the full range of carrier oils and personal care bases at The Skin Science Company all cosmetic-grade, with fast dispatch from our Melbourne warehouse; see our shipping page for current times.
All products from The Skin Science Company are intended for cosmetic use only. Nothing in this article constitutes medical advice or makes therapeutic claims. Always patch-test new ingredients before incorporating them into a full formulation. When making water-based products, always use a validated preservative system and follow good manufacturing practice.
For fatty acid profiles, comedogenic ratings and shelf life of 115 carrier oils and butters, see our Carrier Oils and Butters Data Library.
