TRI Research Forum, will take place on Friday 12th April 2024 (9:00am – 12:40pm ET), and is a chance to discuss possible future directions for TRI. Registration is free and exclusive to employees of TRI Member Companies. Research Forum will be streamed live, and available on playback.
Research Forum is a meeting where the TRI team give you an exclusive overview of the new research they have been doing and the new capabilities they have been developing. It is also a chance for you to give us some guidance on the areas of research that will be of most benefit to your business. It is, as the title suggests, a forum for discussion. A chance for the TRI the listen to what you need from our work.
The format of the meeting will be quite simple. We will have a series of short presentations from our technical Directors, giving you exclusive updates on our internal research programme and news about new equipment purchases. These will be followed by a series of discussions about possible future directions. We are proud the announce that the discussions on future directions will, on this occasion, be led by two independent, TRI Adjunct Fellows: Dr Crisan Popescu, a hair and textiles sciences expert (link to website), and Dr Apostolos Pappas, a skin, nutrition and lipids sciences expert (link to website).
Anyone from our member companies is welcome to take part. No question is too obvious, and no idea is too ridiculous. Please come along and help us build our future research and testing capabilities.
Article By Dr. Xuzi KangPostdoctoral Fellow atTRI Princeton
Ever wonder why the same lipstick looks different on you and your friends? It's not just about the color in the tube; it's a game of “mix and match” with your skin tone. Dr. Xuzi Kang from TRI has been exploring this fascinating interaction and learning how human eye perception and lipstick shades interact.
Color theory of lipsticks:
Like the color theory used in painting, lipstick color theory is a blend of art and science that guides the creation and selection of lipstick shades.
The First Layer - Skin Tone Sets the Stage:
Think of your skin as the canvas and the lipstick as your paint. That first swipe is where the magic begins. Your skin's undertone plays a crucial role here, subtly shifting the lipstick's appearance. A cool undertone might give red lipstick a pinkish hue, while a warm undertone might make it appear more coral.
More Layers, More Drama:
As you layer up, the lipstick starts to reveal its true colors. But even then, your skin tone is like a subtle filter, influencing our perception. This effect is why lipstick might look slightly more intense on lighter skin.
The Color Perception Game:
Our eyes are not just viewers; they're interpreters. They perceive color in context, influenced by surrounding shades. This is why the same lipstick can appear to be a different shade against different skin tones. It's all about how the color interacts with the skin's unique palette.
Delta E (ΔE)
Delta E (ΔE) is a metric that quantifies the difference between two colors in a color space. It's a measure of perceptual color difference, essentially representing how much two colors deviate from each other to the human eye. The term 'delta' signifies a difference or change, while 'E' stands for 'Empfindung,' which is German for 'sensation' or 'perception. Delta E values below 1 represent a barely noticeable color difference to the average person when the colors are separate. In commercial reproduction, a Delta E of 3 to 6 is acceptable, though noticeable to print and graphic experts. Delta E is calculated between skin color and applications to show the color differences with different application layers.
Experimental
Sample lipstick is applied 0.5 (one swipe), 1, 3, and 5 rounds on the inner arm of panelists with Type III and Type VI skin according to the Fitzpatrick skin scale. A portable colorimeter is used to measure the colors of the lipstick application (Figure 1). Delta E is calculated and compared between skin colors and sample applications (Figure 2). We can see that when zoomed in, the skin colors are very different (Delta E is 18.1), but after applying 5 rounds of the lipstick, the colors are almost the same (Delta E is 2), although, from Figure 1, they look very different with different skin color as the background.
Figure 1. The different rounds of swipes of the lipstick application on the arm (left). Testing using a portable colorimeter (right).
Figure 2. Skin color and lipstick application zoomed in and Delta E comparison (left). Delta E of applications on the two skin types (right).
Its significance for claims:
Complementing Skin Tones: By applying color theory, R&D teams can develop a range of shades designed to complement various skin tones. This is crucial for claims like "flattering for all skin tones" or "universal shades." Understanding the interactions between lipstick colors and skin undertones (cool, warm, or neutral) allows for creating shades that enhance natural beauty.
Color Accuracy and Consistency: Color theory ensures that the pigment in the lipstick translates accurately from the tube to the lips. This is essential for claims like "true-to-color" applications. It involves studying how different pigments mix and how they appear when applied, ensuring consistency between batches.
Color Correction Properties: Some lipsticks are formulated with color correction in mind, using principles of color theory to neutralize discolorations or pigmentation in the lips, supporting claims like "color-correcting lipsticks."
☺ At TRI, we offer lipstick testing that measures the properties of the lipstick stick itself (hardness, stickiness, and melting behavior), lipstick spreadability (pay-off and layering friction), color effects, lipstick transfer and longevity, and lip hydration. For details, refer to our previous blogs:
We are pleased to announce that TRI is starting a promotion season for lipstick testing starting now, enjoy a 10% discount for orders placed before June 30th, 2024!
Last time, we talked about various testing methods for lipsticks, you can find them here. Now let’s talk about our lips!
Lips, those soft bits on our faces, do a lot more than help us chat or smile. They're different from the rest of our skin, which means they need a little extra love and care. If you're someone who loves lipstick, it's even more important to know more about the uniqueness of our lip skin.
The Distinctive Nature of Lip Skin
While we often consider our skin as a uniform organ, it varies significantly across different body parts. The skin on our lips, for instance, is incredibly distinctive:
Thin but mighty: Unlike the rest of our body which has between 15 to 16 cell layers, the lip skin is wafer-thin, boasting only 3 to 5 layers [1]. This minimal layering makes lips susceptible to external factors and potential irritants.
Missing moisture mechanisms: One reason your lips might feel dry more often is because they lack sebaceous and sweat glands. These glands are responsible for naturally moisturizing the skin. Plus, lips experience a heightened rate of water loss compared to other skin areas, making them prone to dryness.
Figure 1. Anatomy of lip skin [1].
Given these characteristics, it’s easy to see why lips demand special attention and regular hydration.
A Closer Look at Lip Hydration
At TRI Princeton, Dr. Xuzi Kang employed a corneometer to gain a deeper understanding of lip hydration. This device is both easy to use and non-invasive, making it optimal for accurately measuring the hydration levels in the superficial layers of the lip skin (the stratum corneum) [2]. This feasibility study engages 18 participants (9 male and 9 female) who are systematically chosen from a broad age range of 24 to 68 years old. Five testing points on the lips are chosen to test their upper and lower lip hydration. Participants are selected based on specific inclusion criteria which require them to be devoid of lip pathologies, skin lesions, or evident signs of lip dryness, thereby ensuring the integrity of the data pertaining to lip hydration. The objective was to determine differences in hydration levels between the upper and lower lips.
Figure 2. A: The 5 sampling locations on the lips; B: lower lip is 29% less hydrated than upper lip;
C: most panelists exhibit higher hydration in their upper lips (a), while only a few shows the opposite (b).
The Impact of Lipsticks on Hydration
Hydration is a significant concern for consumers, with some noting that while matte lipsticks do not transfer easily, they can be drying. To provide a deeper understanding of this phenomenon, the corneometer is used to evaluate lip hydration after a 2-hour application of the lipstick. Through a comparative feasibility study of the different types of lipsticks both on the arms and on the lips, distinct characteristics are identified and evaluated.
By analyzing the products' impacts both on the arm and lip skin, significant differences are found in hydration behavior based on the application site, a phenomenon illustrated in Figure 3. Interestingly, lip skin consistently shows a higher hydration level than arm skin, suggesting that lip skin is more susceptible to water evaporation, highlighting the fundamental differences between the two skin types in terms of composition and function.
It is found that all lipsticks tested, regardless of brand or type (including Vaseline - the positive control), enhance arm skin hydration to different extents, ranging from 16% to 67%; while lip skin. It is worth noting that the lip skin, which naturally holds more water, undergoes noticeable changes when in contact with different lipsticks (-13% to 57% hydration increase). This stresses the effect of lipstick formulations on hydration levels, and these data align with panelists' perceptions. Another interesting finding from this study is the hydration level in the upper lips compared to the lower ones, suggesting a possible difference in the anatomical and physiological attributes of the upper and lower lips. It’s worth noting that ATR-FTIR is available at TRI too to reliably measure hydration levels of our skin.
Figure 3. A: Arm and lip hydration levels are different;
B: arm and lip skin hydration change behaviors are different after 2h lipstick application.
Figure 4. There is a relatively strong correlation between hydration test results and panelists’ perception. Panelists rate their perception on a scale of 1 to 10, with 1 indicating very drying and 10 signifying highly moisturizing for the lips.
Wrapping It Up
In conclusion, the lip skin, inherently thinner and lacking sebaceous and sweat glands, is predisposed to quicker drying. Using a corneometer, this study offers a comprehensive examination of hydration levels on the lips and compares them to arm skin after lipstick application. Notably, because of their thin structure, lip skin has a higher hydration level than arm skin, and is more sensitive to different formulations of lipsticks. The application of various lipsticks showcases an impact on lip hydration levels, which correlates with the perceptions of panelists. Furthermore, the study shows a difference between the upper and lower lips in terms of hydration, shedding light on potential variations in their anatomical and physiological makeup. These insights not only deepen our understanding of lip skin hydration dynamics but also emphasize the influence of cosmetic formulations on the skin.
For a deeper dive into this topic, Dr. Xuzi Kang will be presenting at the SCC annual meeting later this year. If you're keen to learn more, we highly recommend attending her session.
2. López Jornet, María Pía, Fabio Camacho Alonso, and Ana Belén Rodríguez Espin. "Study of lip hydration with application of photoprotective lipstick: influence of skin phototype, size of lips, age, sex and smoking habits." (2010).
Looking to launch a new lipstick line or enhance your current line? For more information about lipstick testing methods, contact us.
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