Base makeup, the foundation of a sophisticated makeup look, enhances the effect of makeup and gives the skin a radiant glow. Consumers are demanding more and more from their base makeup, but darkness or darkening is still a common problem with foundation products. Many opinions about darkness exist, but the underlying mechanisms and solutions are rarely reported.
Uni-powder’s R&D scientists took an innovative approach to exploring this problem. They used the foundation liquid as a model to analyze the darkening rate of different hue foundation liquids, simulated the scene of volatilization of the emulsion system and skin oil production after makeup, and then, combined with the theory, explored the potential mechanism of the darkening of the base makeup from the perspective of powder and proposed corresponding solutions.
Key takeaways from this article:
1. Base makeup darkness is not caused by oxidation
Fig.1 Iron Black XPS spectrum in the foundation before and after darkening
From the formula structure, the foundation is mainly composed of water phase, oil phase, and inorganic pigments. It’s widely known that water is stable and demanding to be oxidized in the atmosphere. Oils, primarily saturated fats or silicone oil are also challenging to be oxidized. Pigments that determine the color of the foundation mainly contain titanium dioxide, iron oxide red, yellow, and black (Fe3O4). The metal elements in titanium dioxide, iron oxide red, and yellow are in high valance, stable, and challenging to oxidize further. Only iron oxide black contains ferrous iron (Fe2+) and ferric iron (Fe3+). Fe2+ can oxidize to Fe3+; Fe3O4 is converted into Fe2O3, causing color changes. However, the reaction is difficult to occur quickly under room temperature. To further investigate whether the iron black in the formula is oxidized, X-ray photoelectron spectroscopy (XPS) was used to analyze the changes in iron black composition before and after dimming. As shown in Figure 1, the iron black before and after the darkening are the two prominent peaks, and the typical Fe3O4 spectrum has no new peaks, indicating that the iron black has not been oxidized, and the oxidation of the iron black does not cause the darkening of the base makeup.
2. The underlying mechanism of base makeup darkening
(1) The human eye is more sensitive to red, and the reddish foundation is darker fast and more noticeable.
Fig.2 (a) Chromatic aberration curves of different shades of foundation (b) McAdam colorimetric graph
(2) The weightlessness of the emulsification system causes the base makeup to be darkness
Figure 3. (a) Weight-loss and (b) color difference curves of Sample 3# and Sample 4#. (c) the color difference of Sample 3# and (d) Sample 4# as a function of weight-loss
The emulsification system volatilizes, the gloss of the foundation decreases, the covering power decreases, the skin texture appears, the toner gathers, the surface roughness increases and the scattering and refraction of light are relatively reduced, making the base look dull and dark.
(3) Sebum secretion causes base makeup darkness
Fig.4 Effect of artificial sebum on the color difference of foundation
Before the skin is oily, the light spreads from the air to the surface of the toner, and after the oil, the toner is infiltrated by sebum. The light spreads from the sebum to the surface of the toner, indicating that the medium of light propagation has changed before and after the oil. The refractive index of sebum is greater than that of air, and it is known from Fresnel's formula that the refractive index of the propagation medium becomes larger, the reflectivity decreases, and the light seen by the eye decreases, making the darkening base makeup.
Three solutions for base makeup darkness
(1) Solve the problem of formula compatibility
When the formula system is incompatible, problems such as color floating, demulsification, oiliness, and uneven dispersion will emerge quickly. Therefore, the primary step in combating darkness is to address the issue of formula compatibility, including the compatibility of powder and oil and the compatibility of oil and fat. Applying the right surface treatment can enhance the powder's compatibility in the formulation. It can also give the powder a hydrophobic and sweat-resistant effect and an anti-sebum effect.
(2) Adjust the volatility of the formula
Two ideas: one, slow down the volatilization of the emulsification system and maintain the stability of the system and pigment, which is conducive to slowing down the immediate darkness, but be careful not to add too much moist oil, we found in the experiment that too much moist oil can slow down the immediate darkness, but the long-term darkness will be apparent. The second step is to enhance the volatility of the system so that the system can completely dry within 1 hour after applying makeup. The immediate darkening is very significant, but it can slow down the darkening process for a more extended period.
(3) Reduce the color difference of pigments
Deposition on the surface of the pigment or growth of silica, aluminum hydroxide, and other materials with a refractive index close to sebum, even if the pigment is infiltrated by sebum, will cause a relatively small color difference, which can not only protect the toner but also do not affect the color development.
Oil-controlling ingredients are added to the formula to reduce skin oiliness. Alternatively, oil-absorbing or sebum-curing powders can be added to absorb or fix the oil from the skin, reducing the darkness caused by sebum-infiltrating pigment.
Fig.5 Deposition or growth of silica and aluminum hydroxide on the surface of the toner
(4) Add the brightening powder
Boron nitride, mica, bismuth oxychloride, and other high-gloss powders are added directly to the formula to brighten the base and reduce darkness.
Fig.6. Highlighting boron nitride (left) and compounding of high-gloss powder and toner (right)
Conclusion:
The darkness of the base makeup is not caused by oxidation but by the weightlessness of the emulsification system, the human eye's recognition of color tolerance, sebum infiltration, and finally, the interaction between the base makeup and light. The first step to solve the problem of the darkness of base makeup is to solve the compatibility of the formula, pay attention to the compatibility between powder and oil, and oil and oil, and then appropriately adjust the volatilization rate of the formula system, and then through the composite of silica or aluminum hydroxide and other refractive index and sebum close materials, the introduction of oil absorption or curing sebum materials to reduce the darkness caused by sebum infiltration, and finally add brightening powder to improve the brightness of base makeup, to achieve an excellent anti-darkness effect.
Our SG series has already tested and approved its anti-darkness properties. If you are interested in this paper, don't hesitate to contact us.
Post time: Jul-16-2024