LIPSTICK COLOUR CHANGE ASSOCIATED TO THE VARIATION OF CARMINE CONCENTRATION

The pigment carmine is generated when carminic acid is precipitated with salts. This natural product can be used to colour oil-based cosmetics. The pigment has several advantages, such as a wide colour variation at different pH values, an excellent stability to light, and a lack of side effects due to its natural origin. The objective of this study was to determine how lipstick colour is associated to the variation of carmine concentration. Three lipsticks with different concentrations of carmine were elaborated with two main mixtures. The first mixture involved the melting and homogenization of four different waxes with castor oil. The second mixture was a carmine dispersion in the castor oil in order to remove lumps. The two mixtures were homogenized and the product was injected into moulds where they solidified into coloured lipsticks. Once the bars had solidified, their physicochemical characteristics, including their colour, were analysed. Thus, it was observed that with increasing carmine concentration the colour tended towards red, with a lower brightness with respect to the control lipstick (L* = 27.88 ± 1.35, a* = 19.93 ± 0.99, b* = 2.44 ± 0.07). This will serve in the future to determine the carmine concentration that should be used to make a lipstick of the desired colour.