What is HLB in cosmetic formulas?

How does HLB work in a cosmetic formula?

Remember that emulsifiers have a water loving and oil loving portion:

 

The HLB system is used today to help identify the chemical nature of emulsifiers and the type of emulsion formed through their use. The HLB number is within the range of 1 – 20; and has the characteristics as shown in the table below:

As you can see, those emulsifiers with low HLB will have a higher preference for a lipid continuous phase, compared to those emulsifiers with a higher HLB.

We can recognize what sort of function an emulsifier or surfactant will have by its HLB ‘score’. Where you see a HLB description, it can help describe the suitability of an emulsifier/surfactant to provide a certain function based on the following ‘scores’:
 

How to use the HLB system

You can use the ‘score’ and charge of an emulsifier to help determine which emulsifiers best suit different types of emulsifier formulations. For example:

• If you want to create a high viscosity cream with a relatively high lipid input, you should use an anionic emulsifier paired with a non-ionic high HLB emulsifier blend. The non-ionic emulsifiers help bring mildness to the formula, and you should be pairing the anionic material with a high HLB emulsifier blend to give the best emulsifier packing at the interface between the oil and water phases for the longest stability. Waxy emulsifiers help build a good ‘body’ to the cream. Watch: How to make a body butter for more tips on building viscosity in your emulsion formulas. 
• If you are creating water in oil emulsions, you would choose only waxy and liquid low HLB emulsifiers to help stabilise the relatively high oil input used in these formulas. Watch our video: Creating water in oil emulsions for more guidance. 
• If you are having a white rub-in issue with an oil in water formula, it usually comes from a soaping effect from the emulsifiers. You can try adding a little low HLB emulsifier (around 2%w/w) to reduce this soaping effect – too much would destabilise your formula, but a small input can reduce excessive foaming and make the product feel as if it is absorbed quicker. Watch our Formulation Fix-Its: fixing white rub in time video for more tips.

What are the shortcomings of the HLB system?

While the HLB number provides us with a starting point for the most appropriate emulsifier selection, in practice, the use of HLB has the following shortcomings:

• while the HLB number tells us which emulsifiers are best used for an emulsion, it does not provide us with a quantity that should be used. This is up to trial and error through stability testing to determine. If too much emulsifier is used, the product will spread white on the skin before being absorbed; if too little emulsifier is used, the product will separate before it’s 3 year shelf life.
• the HLB number for an emulsifier is affected by temperature because it relates to the solubility of the emulsifier in the water and oil phases. This solubility varies with temperature changes.
• you can’t use the HLB system with polymeric emulsifiers, but you generally wouldn’t need to unless you want to pair an emulsifier with a polymeric emulsifier for extra viscosity. 

How can you get the HLB value of an emulsifier or blend?

Suppliers will often provide the HLB number of an emulsifier as part of the materials’ technical information; or you can request this information if it is not provided. Where you have a HLB value, you can specifically select emulsifiers (or blends of emulsifiers) to yield you with an average HLB of <8 (4-5 is ideal) for a w/o emulsion; or average HLB of >8 (around 11-12 is ideal) for an o/w emulsion.

Watch our videos: how emulsifiers are different and how to pick the best cosmetic emulsifiers videos for more tips…
 

HLB for cosmetic emulsions: some final tips

Remember that the HLB system is not perfect! It is not a guaranteed prediction of how an emulsifier will work as this will depend on what other emulsifiers are used in the formula, the lipid content, and if any charge is present.

Make sure you are using the HLB system to compliment your cosmetic emulsions rather than relying on it – but it will help speed your selections and possibly improve the creaminess and sensory aspects of your emulsions, especially their shelf life and long-term stability.

Happy formulating!