How to Prevent Base Makeup from Darkening: A Step-by-Step Guide with Uni-Powder

Base makeup, also known as foundation, is one of the top-ranking color cosmetics among consumers for its ability to create a flawless complexion and radiant glow. Formulators are including skincare ingredients and properties to satisfy consumer demands for base makeup that is multifunctional and delivers much more than just a foundation. But there’s a dark side (pun intended)…

Both consumers and cosmetics formulators experience a common frustration with this popular cosmetic – base makeup that darkens over time once applied to skin. 

Uni-Powder’s recent ground-breaking research has revealed new insights into why this darkening occurs (it’s not what you think!) – and how it can be prevented. Our step-by-step guide based on this research debunks myths and helps brands and formulators understand the underlying mechanisms. More importantly, it provides actionable solutions for base-makeup formulations that stay true to color.

Key takeaways from this article

• Base makeup darkness is not caused by oxidation
• The underlying mechanism of base makeup darkening
• Uni-Powder's recommended solutions 

The Science behind Makeup Darkening

Whether you’re in the lab perfecting a new base makeup or tweaking an existing formulation, understanding the causes behind this darkening effect is key to creating products that remain flawless and stable on skin. 

Uni-Powder's Research Methodology

When embarking on this study, Uni-Powder’s research team took a fresh approach to understanding why foundation darkens over time: 

First, they tested different liquid foundation hues to analyze how quickly these darkened, recreating real-life conditions under which the volatile components of the emulsion evaporated (as the formulation dried), as well as how the color and formula changed when exposed to sebum (skin oil).

Using this information, they examined the potential mechanism behind this darkening effect by focusing on how powder particles within the formulation interacted with the other ingredients, particularly during the drying process, in order to understand the underlying mechanisms at play. 

Based on their findings, they then proposed effective solutions to prevent this issue.

Research Results

1. Base makeup darkness is not caused by oxidation

Uni-Powder’s study challenges the conventional wisdom and popular belief that base-makeup darkening occurs primarily due to oxidation. By examining each of the main components of the foundation formula – water phase, oil phase, and inorganic pigments – the study determined that none of these are easily oxidized under normal conditions.

Water Phase: Water is chemically stable and does not oxidize easily in the atmosphere.

Oil Phase: Oils used, such as saturated fats and silicone oils, are also resistant to oxidation. These stable compounds do not react readily with oxygen in typical room-temperature environments.

Inorganic Pigments: Pigments in the foundation included titanium dioxide, iron oxide red, iron oxide yellow, and iron oxide black (Fe3O4). 

Titanium dioxide and iron oxides (red and yellow) are stable because their metal elements are already in high valence (their highest oxidation state). Therefore, these components cannot undergo further oxidation.

The only pigment that contained ferrous iron (Fe2+) is iron oxide black (Fe3O4, or iron black). In theory, Fe2+ could oxidize to Fe3+, and Fe3O4 could convert to Fe2O3, which might change the color of the foundation. However, this oxidation process is slow and unlikely to happen quickly at room temperature.

X-ray Photoelectron Spectroscopy (XPS) Analysis:

Fig.1 Iron Black XPS spectrum in the foundation before and after darkening

To further investigate and confirm whether the iron black had oxidized, XPS was used to compare its composition before and after the foundation darkened.

The results (Fig. 1) show that there were no new peaks in the iron black spectrum, and the typical Fe3O4 peaks were unchanged. This indicates that no oxidation of the iron black occurred during the foundation darkening.

2. What are the underlying causes of base makeup darkening?

Uni-Powder’s research identified several key contributors that cause base makeup to darken. These were mainly due to changes in the formula as it dries:

• Color Perception: The human eye is more sensitive to red, and foundations with a reddish hue are more prone to noticeable darkening, more quickly, which can be more apparent to users.

Fig.2 (a) Chromatic aberration curves of different shades of foundation (b) McAdam colorimetric graph

• Emulsification System Instability: The study highlighted that instability in the emulsification system contributed to foundation darkening. As the emulsion volatilizes (with drying), the foundation loses weight, resulting in reduced gloss and diminished coverage, as well as formula clumping. This weight loss also exposes the skin’s natural texture, increasing surface roughness and reducing its light-scattering and refraction properties, which leads to a more dull and darker appearance. 

Fig. 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

• Sebum Secretion: Sebum has a significant impact on the appearance of base makeup over time. The researchers found that when sebum mixes with foundation, it alters the light refractive index. Before sebum is present, light travels through the air to the foundation’s surface. Once sebum from the skin mixes with the foundation, light passes through the sebum. Since it has a higher refractive index than air, sebum changes how light reflects off the foundation. It causes less light to be reflected back to the eye, making the foundation appear darker.

Fig.4 Effect of artificial sebum on the color difference of foundation

So, how can formulators prevent these factors from happening? This is where Uni-Powder’s innovative approach comes in.

Four step-by-step solutions for tackling base makeup darkness

Step 1: Solve the problem of Formula Compatibility 

When the ingredients in a base makeup formulation are incompatible, problems such as color float, demulsification, oiliness, and uneven dispersion will arise quickly. Uni-Powder’s research highlights the importance of harmonizing pigments with the base formula. This means:

• ensuring compatibility between the powder, oils, fats, and other components.
• using the right surface treatment to enhance the powder's compatibility in the formulation, which can also make it hydrophobic and resistant to sweat and sebum.

Step 2: Adjust the Volatility of the Formula 

Controlling the volatility of the formula by adjusting drying time can impact how quickly it darkens. There are two main approaches:

• Slowing down drying (the volatilization of the emulsification system) to maintain color stability and reduce immediate darkening. However, be cautious not to use too much oil, as this can slow immediate darkening, but it may lead to more darkening over time.
• Speeding up drying by adjusting the formula so it dries completely within an hour of application. While this may cause some immediate darkening, it helps reduce the overall darkening effect in the long run.

Step 3: Reduce Color Changes to Pigments

Pigment quality and uniformity play a huge role in how stable the final product will be. The study points out that variations in pigment size, coating, and processing can lead to uneven darkening. Formulating with high-quality pigments that offer consistent performance is essential.

Coating pigments with materials such as silica or aluminum hydroxide can minimize color changes caused by sebum infiltration. These materials have similar light-reflecting properties to sebum, which helps maintain color consistency even if oil mixes with the foundation. They protect the color as well as not affecting color development. 

Additionally, including ingredients that control or absorb oil in the formula can help to manage skin oiliness and prevent sebum infiltration. This can reduce the impact of sebum on the foundation’s color, keeping it looking fresh and true to shade.

Fig.5 Deposition or growth of silica and aluminum hydroxide on the surface of the toner

Step 4: Add a Brightening Powder

Adding high-gloss powders such as boron nitride, mica, bismuth oxychloride to the formula can help brighten the base makeup, reducing darkness and maintaining its luminosity.

Product Spotlight: Uni-Powder SG Series and Boron Nitride 

Uni-Powder’s SG series has been tested and proven to effectively prevent darkening, ensuring base makeup formulations stay true-to-color throughout the day.

To further optimize formulations, Uni-Powder’s boron nitride offers unique benefits: their wet-peeling technology makes their boron nitride flakes thinner and smoother. Known for its exceptional light-diffusing properties, boron nitride helps to reduce base makeup darkening and gives a silky smooth, luminous finish that keeps consumers happy throughout the day.

Conclusion

Preventing base makeup darkening doesn’t have to be a daunting challenge. Uni-Powder's research gives us compelling evidence that it isn’t caused by oxidation, but by factors including weightlessness with drying of the formula, how we perceive color, and the infiltration of sebum, as well as the interaction between light and the makeup. 

To address these issues, their team of scientists recommend four steps: firstly, ensuring that all ingredients in the formula are compatible. Secondly, adjusting the volatilization rate of the formula and how quickly it dries. Thirdly, using materials that mimic the refractive index of sebum to keep colors true and stable, as well as adding ingredients that control oil. Finally, they recommend including brightening powders in the formula to improve brightness and achieve an anti-darkening effect. This way, brands can develop long-lasting, high-quality base makeup products that solve both formulator and consumer frustrations, and meet their expectations.

👉 To learn more about Uni-Powder’s innovative solutions and see their products in action, visit them at in-cosmetics Latin America (25-26 September 2024) at booth F20, or explore their ingredients online on Covalo. 

References: 
All information in this article is based on Uni-Powder's research