The effect of formulation on the hardness and crystallization of emulsion lipsticks

Emulsions can improve the emollient property of lipsticks because of the introduction of hydrophilic ingredients. A lipophilic emulsifier (Span 60 or Span 80) or a hydrophilic emulsifier (Tween 20) was used to prepare emulsion lipsticks. The experimental results show that a hydrophilic emulsifier is as good as a lipophilic emulsifier. Both of them give stable W/O emulsion lipsticks that also have similar values of hardness (or stiffness). A comparison of physical properties of emulsion lipsticks was made with a conventional lipstick. An emulsifier has a good compatibility with waxes and thus decreases the crystallization, which also decreases the hardness. On the contrary, the formation of emulsion droplets increases the hardness of lipsticks. The effect of water content on the physical properties of emulsion lipsticks is also discussed.