Choosing the right emulsifier for your formulation can be difficult. In an ideal emulsion, the emulsifier is equally attracted to the water phase and the oil phase. If the balance is tipped in either direction, the emulsifier may lose contact with the phase to which it is less attracted, causing the emulsion to break down. Furthermore, it requires trial and errors to get a stable formulation. Emulsifiers do more than ensure stability; they also affect the feel, texture, and properties of an emulsion. It’s therefore important to be well-informed about your options and the effects they will have.
Emulsions are systems composed of two or more immiscible materials, in which one material (the discontinuous or internal phase) is suspended or dispersed throughout another material (the continuous or external phase) in separate droplets. The immiscible phases can be water, oil or silicone.
Emulsifiers are used in creams and lotions to mix water with oils. Since water and oil do not mix but stay separated, an additional agent (emulsifier) is necessary to form a homogenous mixture keeping water and oil together. There are 2 types of emulsifiers. Oil-in-water (o/w) emulsifiers keep oil drops packed in water, while water-in-oil (w/o) emulsifiers keep water drops packed in oil.
HLB system is used to identify the chemical nature of emulsifiers and the type of emulsion formed.
HLB Value | Emulsion formed | Example |
< 8 Low HLB | W/O emulsion | Emulri 6GPR ( Polyglycerol-6 Polyricinoleate) HLB value: 3.0 |
9-15 High HLB | O/W emulsion | Emulri 6GP (Polyglycerol-6 Palmitate) HLB value: 10.5 |
> 15 High HLB | Solubilizer | Emulri 10GCL (Polyglycerol – 10 Caprylate) HLB value: 17.0 |
Types of emulsifiers based on charge:
Product Type | Recommended Emulsifier Inputs |
Serum (o/w) | •Non ionic waxy emulsifier blend •Use low side of recommended dose •Use polymer to stabilize and build viscosity |
Cream gel (o/w) | •Use polymeric emulsifiers •No additional gum/polymer •Non ionic waxy emulsifier: small to mid point of recommended dose for “creaminess” |
Crème cleanser (o/w) | •Anionic high HLB waxy emulsifier: use mid-point of recommended dose •Non-ionic waxy high HLB emulsifier blend: use high side of recommended dose •Use water compatible polymer/gum to stabilize and build viscosity •Excess emulsifier is desired to ensure good cleansing |
Lotion/Cream/ Body Butter (o/w) | •Anionic high HLB waxy emulsifier (if no compatibility issues): mid-point of recommended dose •Non-ionic waxy high HLB emulsifier blend: use high side of recommended dose •Add 2-3% low HLB waxy emulsifier to build viscosity and reduce soaping effect •Use water compatible polymer/gum to stabilize and build viscosity |
Conditioner | •Cationic waxy or liquid emulsifier: use mid to high point of recommended dose •Non-ionic waxy high HLB emulsifier blend: use high side of recommended dose •Use water compatible polymer/gum to stabilize and build viscosity (not cationic) •No chelating agent |
Cream/Lotion (w/o) | •Low HLB waxy emulsifier as primary emulsifier •Low HLB waxy or low liquid emulsifier blend as secondary emulsifier •Add oil compatible polymer •Add NacL or Magnesium sulfate hepta hydrate to water phase to give water charge •Do not use chelating agents. |
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