As for with makeup products, the main aim of a lipstick formula is to release a coloured layer, in this case onto the lips, with a simple and soft application. Even if fair stick softness during distribution is required, an adequate mechanical resistance during application onto the lips should oppose the bending forces involved in this process. The coloured trace must be homogeneous, continuous, without oil stripes (the so-called ‘motorboat effect’), hiding the wrinkles of the lips as much as possible. Moreover, the pigmented layer should stay on the lips pseudo-mucosa, and keep stable for hours in spite of the continuous movements and friction of the lips, not bleeding or diffusing by capillary forces along the wrinkle paths. The layer must be plastic and elastic in order to follow the skin’s movements, be water and saliva resistant, not staining easily surfaces that might came into contact with the lips. Safety for the lips and after ingestion must be granted. Shape stability of the stick over time and at different temperatures, even following transportation in a handbag, is necessary. ‘Sweating’ droplets of oil on the surface should not appear, even in adverse conditions. Detachment from the holding support of the lipstick case must be absolutely avoided.

As the stick surface is continuously exposed to atmospheric oxygen, the formula’s ease of rancidity should be minimized. Microbial contamination is highly unlikely in case of anhydrous formulae; nevertheless, the exposed external layer should not support microbial proliferation following contact with the lips and their resident microflora.

The strategy to adopt for the development of a new lipstick formula requires, as a first step, the definition of the most important characteristics of a modern product. Successively, the identification of the key properties of any innovative ingredient is necessary. Then, a comprehension of the key parameters in the establishment of a stable equilibrium among the different formula components in the solid state is important. Moreover, it is necessary to study the interactions among the new ingredients and the other structural components in the formula. Finally, an evaluation of the sensory properties of the different final formulae for fine-tuning of practical performances needs to be carefully carried out. In this study, a systematic formulation approach tried to obtain a new lipstick formula using a new vegetal-derived emollient (INCLUDING COCO-CAPRYLATE/CAPRATE, HYDROGENATED OLIVE OIL UNSAPONIFIABLES) with sensorial properties similar to some types of silicones. Some application trials of the new raw material were carried out. The following aspects of this ingredient were investigated: Compatibility and thickening with waxes, dispersion power of pigments, and influence on sensory characteristics of the formulated lipstick. This new emollient has been shown to improve some aspects of a lipstick formula, in particular shine, homogeneity, and covering effect.

As with makeup formulations, frequently, blends of different waxes are used in order to obtain increased mechanical properties. Compatibility tests were thus carried out with blends of three different waxes. Each wax was used at 5%, for a total amount of 15%. Below are the viscosity values measured for each blend at T0, after 24 h and 3 months at room temperature.