How to Choose the Right Emulsifier for Creams and Lotions

Choosing an emulsifier is one of the most important decisions you will make when formulating a cream or lotion.

Choose well and you have the foundation for a stable product with the texture, rinse-off and after-feel you want. Choose poorly and even an otherwise promising formula may separate, become grainy, feel waxy or change significantly during storage.

The best emulsifier is therefore not simply the one described as “natural”, “gentle” or “easy to use”. It is the one that suits:

• the type of emulsion you want to make;
• the composition and size of your oil phase;
• your desired viscosity and skin feel;
• your processing method;
• the pH, electrolytes and active ingredients in the formula; and
• the level of stability demonstrated during testing.

This guide explains how to choose an emulsifier, without treating any single rule— including HLB—as a guarantee of success.

What an Emulsifier Does in a Formulation

Oil and water do not form a stable mixture on their own. When the two phases are mixed, one can temporarily break into droplets dispersed throughout the other, but those droplets tend to move together and merge again.

An emulsifier contains both water-compatible and oil-compatible regions. It positions itself at the oil–water interface, helps reduce interfacial tension and forms part of the protective structure around dispersed droplets.

In practical terms, an effective emulsifying system helps:

• create smaller, more evenly distributed droplets;
• reduce the tendency of droplets to merge;
• support a consistent texture;
• keep the emulsion uniform during storage and use; and
• deliver the intended application and rinse-off experience.

An emulsifier does not work in isolation. Droplet size, viscosity, mixing energy, manufacturing temperature, cool-down procedure, packaging and the rest of the ingredient system all affect stability.

Step 1: Decide Which Type of Emulsion You Need

Oil-in-Water Emulsions

In an oil-in-water (O/W) emulsion, oil droplets are dispersed in a continuous water phase.

O/W emulsions are commonly selected for products intended to feel lighter or rinse away more readily, including many:

• facial moisturisers;
• body lotions;
• hand creams;
• cleansing milks; and
• fluid cream products.

The final feel still depends on the complete formula. An O/W emulsion can be light or rich depending on its oil phase, emulsifier, fatty alcohols, polymers and other structuring materials.

Water-in-Oil Emulsions

In a water-in-oil (W/O) emulsion, water droplets are dispersed in a continuous oil phase.

These systems are often chosen when the formulator wants a richer, more occlusive or more water-resistant product. They may be suitable for:

• barrier-style creams;
• cold-weather products;
• protective hand products; and
• specialised colour or sun-care formats.

W/O emulsions usually require an emulsifier specifically designed for that structure. Their processing method and sensory profile can differ considerably from familiar O/W lotions.

Do Not Choose by Product Name Alone

A “cream” is not automatically O/W, and a “balm” is not necessarily an emulsion at all. Likewise, not every serum contains both oil and water.

Define the physical system before selecting the emulsifier:

1. Which phase should be continuous?
2. Does the product contain an oil phase and a water phase?
3. What oil-phase percentage must the emulsifier support?
4. What texture, spread and after-feel are you targeting?
5. Will the product be made by a hot or cold process?

Step 2: Start With the Supplier’s Technical Information

Before calculating anything, read the emulsifier’s technical data sheet and formulation guidance.

Check for:

• INCI name;
• recommended product types;
• whether it forms O/W, W/O or another system;
• recommended usage range;
• suggested oil-phase range or capacity;
• required processing method;
• melting or processing temperature;
• effective pH range;
• electrolyte tolerance;
• compatibility limitations;
• whether a co-emulsifier or stabiliser is recommended; and
• any supplier example formulas.

These details are more useful than choosing an ingredient from its trade name or marketing description alone. If the supplier has designed an emulsifier as a complete self-emulsifying system, follow that system’s guidance rather than forcing it into a generic HLB calculation.

Step 3: Use the HLB System Where It Is Appropriate

The Hydrophilic–Lipophilic Balance, or HLB, is a numerical system associated with the balance between the water-compatible and oil-compatible portions of certain surfactants.

In broad terms:

• lower-HLB emulsifiers are more oil-compatible and are commonly associated with W/O systems;
• higher-HLB emulsifiers are more water-compatible and are commonly associated with O/W systems.

HLB is particularly useful when working with emulsifiers and oil phases for which reliable HLB and required-HLB data are available. It is not a universal scoring system for every modern emulsifier, polymeric emulsifier, natural emulsifying system or pre-blended emulsifying wax.

Treat HLB as a screening tool—not proof that an emulsion will remain stable.

What Is the Required HLB of an Oil Phase?

Each oil-phase material may have a published required HLB for the emulsion type being developed. The required HLB of the complete oil phase is calculated as a weighted average.

Use this equation:

Required HLB of oil phase = Σ (fraction of each oil-phase ingredient × its required HLB)

The “fraction” refers to the proportion of that ingredient within the oil phase—not necessarily its percentage in the full formula.

Required-HLB Example

Imagine that your oil phase contains:

• 70% Oil A, with a required HLB of 7; and
• 30% Butter B, with a required HLB of 9.

The calculation is:

(0.70 × 7) + (0.30 × 9) = 7.6

Your starting target is therefore an emulsifier system with an HLB close to 7.6, provided the published values apply to your intended emulsion type and materials.

How to Match an Emulsifier Blend to the Target HLB

If one emulsifier does not match the target, formulators may combine a higher-HLB and lower-HLB emulsifier.

The fraction of the higher-HLB emulsifier can be calculated as:

Fraction of high-HLB emulsifier = (target HLB − low HLB) ÷ (high HLB − low HLB)

The lower-HLB emulsifier makes up the balance of the emulsifier blend.

For example, to target an HLB of 7.6 with emulsifiers of HLB 4.3 and 15.0:

• high-HLB emulsifier: approximately 30.8% of the emulsifier blend;
• low-HLB emulsifier: approximately 69.2% of the emulsifier blend.

This tells you the ratio within the emulsifier blend. It does not tell you the total amount of emulsifier the formula needs. Select the total use level according to supplier guidance and the demands of the formulation.

Step 4: Check the Total Oil Phase and Usage Rate

The emulsifier must be able to support the type and amount of oil-phase material in the product.

When reviewing your oil phase, include all relevant lipophilic materials, such as:

• carrier oils;
• butters;
• waxes;
• oil-soluble active ingredients;
• oily extracts;
• fragrance or essential oils; and
• oil-soluble antioxidants.

Do not assume that every emulsifier works at the same percentage. Recommended ranges vary by ingredient and by formulation.

Too little emulsifier can leave the system vulnerable to separation. More is not automatically better: an unnecessarily high level may increase cost, create drag, produce a waxy or soapy feel, interfere with the desired viscosity or reduce sensory elegance.

Work within the supplier’s recommended range, then optimise through controlled trials.

Step 5: Build Texture Deliberately

An emulsifier’s first job may be emulsification, but the emulsifying system also affects viscosity, structure, slip, rub-in and after-feel.

Some emulsifying waxes provide significant body. Other emulsifiers create fluid emulsions and need additional rheology support.

Depending on the formula, that support may come from:

• fatty alcohols such as cetyl alcohol or cetearyl alcohol;
• fatty acids such as stearic acid;
• gums;
• cellulose derivatives;
• synthetic or natural polymers; or
• other co-emulsifiers and consistency agents.

Read more about cetyl alcohol, stearic acid and cetearyl alcohol in creams and lotions.

Emulsifier vs Co-Emulsifier vs Thickener

These terms are related, but they are not interchangeable:

• A primary emulsifier provides the main interfacial support needed to form the emulsion.
• A co-emulsifier assists the primary emulsifier and may improve structure or stability.
• A thickener or rheology modifier changes flow and viscosity, which can slow droplet movement, but it does not automatically replace a suitable emulsifier.

A lotion can be thick and still be unstable. Viscosity may delay visible separation without correcting a poorly matched emulsifying system.

Step 6: Choose the Correct Processing Method

Some emulsifiers require hot processing. Others are designed for cold processing or allow specific one-pot methods.

For a hot-process emulsion, the general workflow may involve:

1. Preparing the oil and water phases separately.
2. Heating as directed so that all required ingredients are fully melted or dispersed.
3. Combining the phases at the supplier’s specified temperatures.
4. Applying appropriate mixing or homogenisation.
5. Continuing controlled mixing while the emulsion cools.
6. Adding heat-sensitive cool-down ingredients at suitable temperatures.
7. Checking and adjusting pH where appropriate.

This is a general framework, not a universal method. Always follow the technical guidance for the actual emulsifier and ingredients in your formula.

Processing problems can resemble ingredient incompatibility. Inadequate melting, mismatched phase temperatures, insufficient mixing or an unsuitable cool-down procedure may all cause graininess, inconsistent viscosity or delayed instability.

Step 7: Check Compatibility With pH, Electrolytes and Actives

A simple base may look stable until an active ingredient, salt, acid or preservative is added. Test the complete formula—not only the base.

pH

Every emulsifier system has a working range. If your product contains acids or other pH-sensitive ingredients, confirm that the final target pH suits:

• the emulsifier;
• the preservative;
• the active ingredients; and
• the intended product format.

Review how to test and adjust the pH of skincare products early in development rather than treating pH as a final cosmetic adjustment.

Electrolytes

Mineral salts, ionic active ingredients, some botanical materials and certain preservative components can alter viscosity or disrupt some emulsifying systems.

If the formula contains electrolytes:

• check the supplier’s tolerance data;
• add the material at the recommended phase and temperature;
• test several controlled prototypes if needed; and
• monitor both immediate viscosity and changes during storage.

Active Ingredients and Solvents

Acids, high levels of humectants, alcohol, glycols, powders and concentrated extracts can change the behaviour of an emulsion.

Do not assume that an active can simply be added to a stable base. Confirm solubility, phase of addition, temperature sensitivity, pH requirements and compatibility with the complete emulsifying system.

Step 8: Make Small, Controlled Trial Batches

Change one important variable at a time. This makes failures easier to diagnose.

A practical screening series could compare:

• different emulsifier use levels within the supplier’s range;
• one or more co-emulsifier levels;
• different oil-phase percentages;
• a suitable HLB blend ratio, where relevant; or
• an alternative emulsifier designed for the required pH or electrolyte load.

Record:

• exact percentages;
• ingredient trade names and INCI names;
• supplier and batch details;
• heating and addition temperatures;
• mixing equipment, speed and time;
• pH;
• appearance, odour and texture;
• fill weight and packaging; and
• observations at each test interval.

Without good batch records, it is difficult to identify why one prototype worked and another failed.

Step 9: Troubleshoot the Failure Pattern

Complete Separation

If distinct oil and water layers form, investigate:

• an unsuitable emulsifier for the emulsion type;
• insufficient emulsifier;
• an oil phase outside the system’s supported range;
• an incorrect HLB match where the HLB method applies;
• ingredient incompatibility;
• processing errors; or
• inadequate mixing.

Creaming or Sedimentation

Creaming occurs when dispersed droplets concentrate toward the top; sedimentation is the corresponding movement toward the bottom. The product may not yet show complete phase separation, but the movement is a warning sign.

Possible causes include:

• large droplet size;
• insufficient continuous-phase viscosity;
• inadequate homogenisation;
• density differences; or
• a weak interfacial film.

Graininess

A grainy texture may result from:

• incomplete melting;
• crystallisation of waxes, butters or fatty materials;
• an unsuitable cooling profile;
• poor dispersion; or
• ingredient incompatibility.

Do not automatically blame the emulsifier. Examine the complete oil phase and manufacturing method.

Viscosity Drift

A product that becomes substantially thicker or thinner over time may be responding to:

• pH drift;
• electrolytes;
• polymer hydration;
• changes in the internal structure;
• temperature exposure; or
• incompatibility between the emulsifier and other rheology modifiers.

A Practical Emulsifier Troubleshooting Checklist

Before reformulating everything, confirm the following:

• Is the emulsifier designed for the intended O/W or W/O system?
• Is the total oil phase within the supplier’s recommended range?
• Is the emulsifier used within its recommended range?
• If HLB applies, were the oil-phase fractions and required-HLB values checked?
• Were temperature-sensitive and heat-sensitive ingredients added correctly?
• Were the phases processed at the required temperatures?
• Was enough mixing or homogenisation applied?
• Is the final pH within the working ranges of the emulsifier, preservative and actives?
• Could electrolytes, solvents, powders or extracts be disrupting the system?
• Is the packaging compatible with the formula?
• Was the complete formula tested rather than only the base?

Step 10: Validate the Emulsifier Through Stability Testing

A successful first batch does not prove long-term stability. Testing should be planned around the product, packaging, intended storage conditions and applicable quality requirements.

A development programme may include:

• Room-temperature observation: Keep a control sample under normal conditions and monitor it over time.
• Elevated-temperature storage: Observe how the product changes under controlled heat stress.
• Low-temperature storage: Check for crystallisation, graininess and phase changes.
• Temperature cycling or freeze–thaw testing: Assess the effect of repeated temperature stress where appropriate for the product.
• Centrifuge screening: Use controlled centrifugal force as an early comparison tool for prototype robustness.
• Packaging-compatibility testing: Store the finished formula in the intended pack and check for leakage, distortion, corrosion, sorption, evaporation or dispensing problems.
• Real-time stability testing: Continue observation under the intended storage conditions.

At suitable intervals, assess:

• appearance and homogeneity;
• separation, creaming or sedimentation;
• colour and odour;
• pH;
• viscosity or flow;
• fill and packaging condition; and
• any product-specific quality attributes.

Accelerated testing can reveal weaknesses and help compare prototypes, but it does not by itself guarantee a particular shelf life. Document the protocol and acceptance criteria before testing begins, and seek qualified laboratory or regulatory support when developing products for sale.

How to Compare Emulsifier Options

Question	Why It Matters
Does it form O/W or W/O emulsions?	The emulsifier must suit the intended continuous phase.
Is it a complete system or an individual surfactant?	Complete systems may have supplier-specific rules that are more useful than generic HLB matching.
What oil-phase range can it support?	A light lotion and a rich cream place different demands on the system.
What is the recommended usage rate?	The correct range supports stability without unnecessarily compromising skin feel.
Is it hot- or cold-process?	This affects equipment, production time and heat-sensitive ingredients.
What pH range does it tolerate?	The final pH must suit the whole formula.
How tolerant is it of electrolytes?	Salts and ionic materials may alter viscosity or stability.
What texture does it create?	Emulsifier choice affects slip, drag, richness and rinse-off.
Does it need a co-emulsifier or thickener?	Additional structure may be required.
Is supplier documentation available?	Technical and safety documents support responsible development and record-keeping.

A Simple Decision Path

Use this sequence when choosing an emulsifier:

1. Define the product. Decide on O/W or W/O, oil-phase level, viscosity, skin feel and processing method.
2. Shortlist suitable systems. Use supplier applications and technical documentation.
3. Check the oil phase. Confirm capacity and calculate required HLB where the method is relevant.
4. Review compatibility. Check pH, electrolytes, actives, solvents, preservative and packaging.
5. Choose a starting use level. Stay within documented supplier guidance.
6. Build structure intentionally. Add a co-emulsifier or rheology modifier only for a clear purpose.
7. Make controlled prototypes. Change one key variable at a time and keep full records.
8. Test the complete product. Include the final actives, preservative, fragrance and intended packaging.
9. Evaluate stability and sensory performance. A stable product must also meet the desired user experience.
10. Repeat if necessary. Reformulation is part of development, not evidence of failure.

Choosing Between a Classic Emulsion and an Oil-to-Milk System

Not every product that interacts with water is a conventional cream or lotion.

Oil-to-milk emulsifiers are often used in anhydrous oils or balms that transform on contact with water and rinse away more easily. They serve a different formulation purpose from the primary emulsifier used to create a water-containing lotion.

For a transforming cleansing oil or balm, consider an option such as Durosoft PG4-O oil-to-milk emulsifier. For a conventional lotion or cream, select an emulsifying system specifically documented for that emulsion type and oil-phase range.

Explore the DIY Naturally emulsifier range to compare options, then verify the technical information for the individual product before formulating.

Formulating for Sale in South Africa

If you plan to sell the finished product, emulsifier selection is only one part of responsible product development.

Keep the following in your formulation file:

• the ingredient’s correct INCI name;
• supplier technical and safety documentation;
• the final quantitative formula;
• manufacturing and batch records;
• stability and packaging-compatibility records;
• preservation and microbiological evidence appropriate to the product; and
• the rationale for the final use level.

Confirm current South African cosmetic, consumer-protection, labelling and safety requirements before placing a product on the market. Where necessary, consult a suitably qualified cosmetic safety, regulatory or laboratory professional.

Frequently Asked Questions

Final Takeaway

Choosing an emulsifier is a process, not a guess.

Start by defining the emulsion and the user experience you want. Use supplier documentation to build a shortlist. Apply required-HLB calculations when they are relevant, but do not rely on HLB alone. Check oil-phase capacity, processing method, pH, electrolytes, actives and rheology. Then make controlled prototypes and validate the complete product in its intended packaging.

The best emulsifier is not the one with the most attractive label or the highest HLB number. It is the one that repeatedly delivers the required stability, texture and use experience in your specific formulation.

For practical examples, see:

• DIY moisturiser formulation with squalane oil
• How to formulate a body butter
• How to test and adjust skincare pH
• Cetyl alcohol, stearic acid and cetearyl alcohol in lotions and creams
• Shop emulsifiers