Article by: Kelly Dobos
Eosine dyes used in cosmetic literally stain the skin, producing a blue red/tint. Incorporated at low level they can add to long-wear properties of lipstick. These stains were the basis for the low cost mood lipsticks of the 70s and their use is becoming popular again with sophisticated lipsticks, glosses, and even blush.
Bright shades of aluminum lake pigments with low opacity are used to impart color to the stick with out significant pay-off, or color on application to the skin. If other pigments are used, they should be used in amounts that will not provide a covering effect upon application.
The eosine dyes do not affect the visual color of the stick but as they are able to stain the skin they will leave a color on application, which is difference from the visual color of the stick. The dyes react with skin pH to create some color variation from person to person. A small amount of citric acid can be used if no coloration of the stick or base is needed.
Below is an example of a formulation for a lipstick that is green but turns pink in the lips.
Premix pigments and citric acid into sufficient castor oil (Part A) and disperse through a 3-roll mill twice. Mix and melt all wax and oil ingredients (Part B), heating to 80 – 85°C. Mix in preservatives (Part C) until fully dispersed. Add pre-milled pigments, citric acid, and castor oil (Part A). Mix until homogeneous. Cool batch to 55 – 60°C and pour into molds.