Why brows turn gray?

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1. Background

The conundrum of pigments, particularly in eyebrows, developing a gray hue is a frequent query among PMU artists. Unraveling the reasons behind this and pinpointing prevention methods may seem daunting initially, but it becomes apparent with deeper insight. This article distills knowledge gathered from discussions with 46 seasoned PMU artists and integrates findings from research undertaken by Powderbrows.com Research Center spanning from 2019 to 2023, including ongoing studies. The collective expertise of 32 artists from the EU, nine from the UK, and 5 from the US contributes to this analysis. Further depth is added through consultations with two chemists, a dermatologist, and an optometry expert specializing in physics, ensuring a comprehensive distillation of the data for broader comprehension.

Despite a unanimous consensus among artists regarding the accuracy of the statements presented, it's critical to recognize that even experienced professionals can have many misconceptions about pigment behavior within the skin.

Our aim with this article is to demystify the underlying causes of the grayish hues observed in semi-permanent brow pigments and to offer practical solutions for practitioners in the field.

2. "Red" as a solvable problem to a degree

The transformation of semi-permanent makeup pigments to shades of gray or blue in the skin is predominantly associated with the carbon content present in the pigments, which are organic components. This contrasts the reddening of brows, which is usually linked to the interaction between inorganic or mineral components, such as iron oxides, with elements within the skin, like the protein ferritin.

Iron Oxide-Based Colorants

Iron oxides are a fundamental component in the palette of pigments used for semi-permanent makeup because of their natural affinity for the skin and the wide spectrum of colors they provide. However, the long-term stability of these pigments can be compromised by their tendency to undergo oxidation-reduction (redox) reactions. Influenced by environmental factors such as UV light, the skin's pH, and various biochemical interactions within the body, redox reactions involving proteins like ferritin are commonplace.

The proclivity of iron oxide pigments to alter their oxidation state, particularly when in a pure, unmodified form, can result in an unwanted shift in color. For instance, magnetite (Fe3O4), composed of iron in multiple oxidation states, may be prone to oxidation, potentially leading to a color shift towards an undesired reddish tone. The cosmetic industry counters this challenge by adopting silanization—a technique borrowed from other technological domains.

Silanization entails treating iron oxide particles with silane compounds to form a protective barrier around each particle. This barrier is instrumental in stabilizing the pigment, thereby preserving its original color and mitigating changes in its oxidation state due to environmental exposure. By chemically bonding silane groups to the iron oxide particles, the pigments' surface chemistry is modified, which enhances their resistance to the natural degradation processes that can occur within the skin.

3. "Gray" as inevitable

Avoiding "red" brows

For pigments containing iron oxide where the concern is "brows turning reddish," the discoloration can indeed be significantly reduced through chemical modification techniques that create hybrid pigment molecules. This is achieved by combining the inorganic iron component with an organic matrix, such as organometallic silica, resulting in a more stable pigment that is less prone to oxidative changes. This fusing process not only helps to maintain the integrity of the original hue but also enhances the overall safety and performance of the pigment when introduced to the complex environment of the skin.

Gray “as a given of small carbon particles”

Moving on to the challenge of "brows turning grayish" due to carbon content, there is a certain degree of inevitability to this occurrence. When pigments with fine carbon particles are used, they are subject to the skin's unique environment and physiological processes that may lead to a gradual shift toward grayish tones. This is mainly because these tiny carbon particles have a high surface area that interacts with the surrounding tissue, leading to changes in how they absorb and scatter light over time, thus altering the perceived color.

While it is true that the grayish color shift is, to some extent, unavoidable, it's not entirely beyond control. The extent to which several factors, such as the size and shape of the carbon particles, the depth of implantation, and the density of the pigment application, can influence the color changes. Precise techniques during the application can minimize particle migration and accumulation, thus reducing the rate at which the color fades or turns gray.

Thus, while the shift to reddish tones in iron oxide-based pigments can be mitigated through chemical modifications, the shift to grayish tones in carbon-based pigments is a more challenging issue that can be managed to some extent but not entirely avoided due to the inherent properties of carbon and its interaction with the body's biological systems.

4. Why brows turn gray

We have established that brows made with organic pigments containing carbon turn grayish in time. Next, we shall delve into that more specifically to explain the actual reasons for that. In the following explanation of why organic pigment turns grayish in the skin, we shall make the following case that consists of three sections.

Understanding Lightfastness

This section will detail the inherent stability of carbon black pigments (CI 77266) against light and how this influences their long-term appearance in the skin. It's essential to address how carbon black behaves in isolation within the skin when not subject to external factors, particularly its interaction with and resistance to light exposure.

Molecular Structure as the Secondary Cause

We will delve into the molecular structure of carbon-based pigments, emphasizing the role of covalent bonding in carbon molecules. This segment will explore how these strong molecular bonds contribute to the pigments' resistance to metabolic breakdown within the skin. Thus, we will recognize the molecular structure and covalent bonds of carbon as significant yet secondary contributors to pigment retention.

Particle Size as the Primary Cause

The focal point of this argument will be the particle size of pigments and its dominant role in determining the retention and stability of carbon particles within the skin. We will discuss how the dimensions of these particles influence their potential to be engulfed by phagocytes, their capacity for migration within the dermal matrix, and their tendency to aggregate. A thorough comparative analysis of particle size against molecular structure will underscore the critical nature of particle size in the retention and degradation processes of carbon particles in semi-permanent makeup.

5. Understanding Lightfastness

What is lightfastness

One critical element that affects the durability of the mixed color permanent makeup is lightfastness. Simply put, lightfastness is the ability of a pigment's components to resist fading or color alterations when exposed to light sources, such as the sun's UV rays or artificial lighting.

Pigment ingredients with consistent lightfastness ensure the color remains stable and true-to-tone over time. Ingredients that are more resistant to light-induced fading usually have higher lightfastness. This trait is particularly important in pigments with larger and more complex chemical structures, as these are generally more stable and less susceptible to breaking down.

The Blue Wool Scale

The industry-standard method for measuring a pigment's lightfastness is through the Blue Wool Scale, which ranges from 1 to 8. A score of 1 indicates the least lightfast or least stable, while a score of 8 signifies the most lightfast or most stable. This scale is an essential tool for artists when custom-blending colors because it informs you of each pigment's resistance to fading, affecting the permanent makeup's longevity.

Once the pigment is in the skin, it will naturally begin to fade and degrade over time. This process is accelerated by exposure to various light sources. If a pigment's ingredients have varying levels of lightfastness, they can fade at different rates. This uneven fading can lead to an inconsistent color that may appear patchy or discolored. For example, some existing pigments and inks are known to age into either an ashy or warm hue over time due to this inconsistency.

6. Degradation of different Colorants

In the realm of semi-permanent makeup, it is recognized that pigments containing carbon black (CI 77266) often include additional organic compounds to achieve various shades, including yellow, orange, or red. There is both a consensus among artists and substantial chemical evidence indicating that the lightfastness index of these supplementary colorants—rated on the Blue Wool scale—is considerably lower compared to carbon black, which has the highest rating of 8. From the standpoint of physical lightfastness properties, it can be inferred that these compounds are more susceptible to photodegradation and, thus may fade from the skin more rapidly than carbon black.

Titanium Dioxide as an Accelerant of Degradation

Manufacturers may label their products to suggest that all colorants possess similar retention properties. Such claims are marketed with the assertion that the pigment will not prematurely fade to gray. Nevertheless, these assertions must be scrutinized critically. One factor to consider is the inclusion of titanium dioxide (CI 77891) in the pigment formulation. When present, particularly in small particle sizes (around 100 nm or smaller), titanium dioxide can act as a UV reflector. This reflection can exacerbate the degradation rate of red and yellow colorants, leading to their accelerated disappearance from the skin beyond what their lightfastness index alone might suggest.

Empirical observations have shown that certain colorants can fade significantly within just the first six months post-implantation. It is, therefore, imperative to consider the overall composition of the pigment formula when evaluating its longevity.

TiO2 high reflective index

Titanium dioxide is widely known for its high refractive index and strong UV light scattering abilities, which is why it's commonly used in sunscreen formulations to protect the skin from UV radiation. When TiO2 nanoparticles are included in a mixture with other organic colorants, they can scatter incoming UV light more effectively due to their small size and high surface area.

This increased scattering can indeed lead to a couple of potential outcomes:

Increased Exposure. Other colorants mixed with TiO2 may be exposed to a broader spectrum of light wavelengths as the UV light is scattered, potentially increasing the rate at which these colorants absorb photons and undergo photodegradation.

Catalytic Activity. TiO2 is also a photocatalyst, which can facilitate certain chemical reactions upon absorbing UV light. While this property is beneficial in some applications (like self-cleaning surfaces and pollution degradation), in the context of pigments, it can lead to the catalytic breakdown of nearby organic molecules, including organic colorants.

Chemist reviewing the article has noted: It's important to note that the overall impact of TiO2 on the degradation of other colorants within the skin depends on several factors, including the concentration of TiO2, the stability of the organic colorants, and the formulation of the pigment mixture. However, the presence of nano-sized titanium dioxide in a mixture with organic colorants can indeed potentially accelerate the photodegradation of those colorants due to enhanced UV scattering and photocatalytic activity. The actual degradation rate would be influenced by the specific formulation and the environment in which the pigments are placed.

That explains why brows are gray after some time (when the degradation of other colorants), but it does not explain why brows remain gray after that. For that, we shall look into the molecular structure of the organic compounds.

Examples of Rapidly Fading Colorants

Some specific colorants known for their rapid fading from the skin include:

Reds: CI12477, CI12310, CI12466, CI12514, CI12150, CI12315, CI12355, CI58000, CI16035, CI45380, CI45430, CI45160, CI15585:1.
Yellows: CI21100, CI21090, CI21095, CI75300, CI75100, CI19140:1, CI19140, CI47005, CI13015.
Oranges: CI21110, CI21160, CI21115.

Conclusion on Lightfastness Impact

Consequently, lightfastness is a pivotal factor explaining why carbon black (CI 77266), with superior lightfast qualities, remains in the skin after other colorants have faded due to UV-induced photonic reactions. This substantiates the initial part of our argument, illustrating that lightfastness is instrumental in the persistence of carbon black relative to other colorants typically combined with it to produce various hues in semi-permanent makeup applications. Therefore, it can be said that photodegradation differences between the carbon black colorant and other colorants are the cause of why brows “become” grayish. However, it does not explain why brows remained grayish after that. For that, we shall look into the molecular structure of the organic compounds.

7. Carbon molecules and gray brows

Molecular structure is the secondary cause of retention

Some experts have suggested that the persistence of carbon molecules in the skin may be due to their robust covalent bonds, which provide a strong molecular structure compared to the ionic structures of inorganic molecules. Let's examine this proposition further.

Inorganic Iron Oxide Particles

Inorganic iron oxide particles are characterized by an ionic atomic structure, with iron atoms forming a crystalline lattice with oxygen, held together by ionic bonds. These pigments, commonly found in the forms of hematite (Fe2O3) and magnetite (Fe3O4), are relatively stable due to these strong bonds. These iron oxides, when used as pigments in semi-permanent makeup, usually come in two oxidation states: Fe2O3 (hematite) and Fe3O4 (magnetite), which contain iron in the +3 and +2/+3 oxidation states, respectively. In the skin, the charged nature of these particles influences their interaction with the biological environment, which is replete with charged entities such as ions and proteins, including ferritin.

The interactions fostered by the iron oxides' surface charge may lead to changes in the oxidation state of iron, potentially causing pigment degradation or color changes. Despite this, the robust ionic bonds typically impart greater stability to these inorganic particles when compared to organic pigments.

Organic Components such as Carbon

Carbon-containing organic pigments are built with covalent bonds, where electrons are shared more equally between atoms, leading to a lower degree of charge separation compared to the ionic bonds of iron oxides. Organic pigments encompass various molecular structures, from simple carbon blacks to complex synthetic dyes.

These organic structures are subject to various degradation processes within the skin, including enzymatic breakdown by skin metabolism and photodegradation from UV exposure. The susceptibility to UV degradation explains why certain organic pigments, particularly those imparting red, yellow, and orange hues, may degrade more readily.

Unlike inorganic pigments, organic molecules lack strong ionic interactions, rendering them more vulnerable to degradation. Moreover, the complexity and size of these organic molecules may make them more prone to fragmentation. However, it's crucial to recognize that these molecules typically form the outermost layer of a pigment particle, and degradation usually occurs layer by layer.

Comparative Degradation

Given the differences in molecular structure, iron oxide inorganic pigments can generally be regarded as more stable than organic carbon-based pigments in semi-permanent makeup. The ionic bonds in iron oxides render them less susceptible to the enzymatic reactions that commonly result in pigment breakdown.

Conclusions on molecular structure as the secondary cause of retention

Therefore, it is not accurate to claim that organic compounds persist in the body simply because of their covalent structures nor to suggest that inorganic compounds degrade solely due to their ionic nature.

In fact, based on the molecular structure and atomic bonds alone, one could argue that the ionic structure of inorganic molecules does not inherently render them more susceptible to degradation than the covalent structures found in organic compounds. The actual reasons behind the differential degradation rates are multifaceted.

The reason the molecular structure of Carbon can be considered the secondary cause for retention in the skin is related to the fact that the way the carbon molecules can be formatted to desired size particles, not for the molecular properties that it presents in the skin.

8. Colorant particle size and gray brows

Understanding Particle Size as the Primary Cause of Retention

In examining carbon black in the context of semi-permanent pigmentation, it is crucial to recognize that the color index CI 77266 encompasses at least three distinct substances differentiated by production methods, leading to varying particle sizes.

Channeling: Known as "Black 6" or "Channel Black," this variant is produced from crude oil and gas with the smallest particle sizes ranging from 90-100 nanometers. It contains approximately 19% organic hydrocarbons and 81% inorganic elemental carbon. The pigment yields a deep black with a bluish undertone and is lightweight, not easily settling into the skin, often used for eyeliners and shading techniques.

Furnacing: Referred to as "Black 2," "Base Black 2," or "Furnace Black," this type is created from petroleum oils in a furnace, resulting in a medium particle size of 200-300 nanometers. It comprises 55% organic hydrocarbons and 45% inorganic elemental carbon. The greenish-black color of this pigment allows for relatively easy skin penetration, making it suitable for eyeliner line techniques.

Thermal Processing: Often termed "Black 7" or "Thermal Black," this pigment is primarily derived from ethylene gas and represents carbon in a nearly free state. With the largest particle size—up to 500 nanometers—and composed of 1% organic and 99% inorganic elemental carbon, this brownish-black pigment is harder to apply, making it suitable for eyebrow and powdering techniques.

The retention of Carbon in the skin is closely linked to the size of its particles and their chemical properties. Particle size can significantly affect carbon retention through the following mechanisms:

Aggregation: Particle aggregates, possessing a larger overall size and different surface properties, are more likely to be detected and processed by the immune system. However, if the carbon particles contain a higher proportion of organic hydrocarbons, they may form looser aggregates that could disassociate and migrate deeper into the skin.

Molecular Stability: Carbon and hydrocarbon molecules consist of stable carbon-carbon and carbon-hydrogen bonds that are not readily broken down by skin enzymes or cells. Carbon-carbon (C-C) and carbon-hydrogen (C-H) bonds are among the strongest and most stable in organic chemistry, and they are not typically broken down by enzymes or cells in the skin without specific biochemical processes to target them.

Less Immune Reactions: Carbon particles are generally less immunogenic than iron oxides, provoking a milder immune response and, consequently, reduced phagocytosis and removal. Some studies suggest that there is practically no foreign body reaction to certain carbon compounds.

Phagocytosis: Large particles, especially those exceeding 0.5 μm (500 nm), are more prone to phagocytosis by macrophages. Scientific studies indicate that phagocytosis is less efficient for particles smaller than 100-200 nm, allowing such particles to remain longer in the dermal layer. However, it's important to note that while smaller particles may evade phagocytosis, they can still be taken up by other processes such as pinocytosis or receptor-mediated endocytosis. This, among many other reasons, is related to the gradual decrease of carbon from the skin.

Compatibility with the skin's lipid matrix: Organic compounds, compatible with the skin's lipid matrix, can distribute more evenly, reducing the likelihood of encapsulation and elimination. For instance, "Furnace Black" (Black 2) is empirically known to integrate easily into the skin. That is also the reason why organic pigments can be used for oily and thick skin much more effectively than inorganic.

pH Levels: The pH of pigment particles can also influence their compatibility with the skin. Particles with sizes yielding pH values that align with the skin's environment may exhibit improved retention.

In conclusion, particle size emerges as a primary determinant of the retention of carbon black pigments in semi-permanent makeup applications. While the molecular structure contributes to stability, the physical dimensions of the particles primarily govern their behavior within the skin, affecting everything from immune response to solubility and migration. This forms the basis for understanding why certain carbon-based colorants persist in the skin, underscoring the pivotal role of particle size in the retention and degradation of pigments.

9. Prevent brows turning gray

The antidote to Brows Turning Gray

As we have established, it is impossible to prevent the graying shade of Carbon in the skin entirely. However, measures can be taken to alleviate this issue. There are three primary methods to mitigate the gray appearance:

Using Larger Particle Sizes

Carbon Black in the form of Thermal Black (Black 7) has a particle size of around 500nm. This size increases the likelihood of phagocytosis by macrophages, but more crucially, it absorbs violet and purple light, reflecting back lighter colors such as blue, green, and yellow. This results in a relatively warmer, more brownish appearance in the skin compared to the smaller particle size variants of CI 77266.

Avoiding Too-Deep Implantation

The Tyndall effect, along with the potential migration of pigment when implanted too deep, exacerbates the grayish undertone reflected by Carbon in the skin. Although complete avoidance of this effect is challenging due to the mobility of smaller particles, careful implantation practices can reduce the occurrence and impact of this phenomenon.

Decreasing the quantity of Carbon

Artists should strive to gain as much knowledge as possible about the pigments they use. While it is unrealistic to expect producers to disclose information that could be perceived as negative voluntarily, artists can make educated guesses about the carbon content by analyzing other elements in the pigment mix.

Moreover, one should avoid using carbon-based colorants on skin areas already containing high amounts of carbon. Novice artists sometimes incrementally increase the skin's carbon content, leading to a saturation point where the effect of other colorants is merely temporary. Fortunately, carbon can be effectively removed with laser procedures.

By adopting these strategies, artists can significantly reduce the likelihood of semi-permanent makeup turning an undesirable gray and maintain the intended coloration as closely as possible.

10. Conclusions

Many artists conflate the properties of carbon molecules with those of the carbon black colorant (CI 77266) when discussing its persistence in the skin. Often, they correctly attribute the stability of small carbon black colorant particles (around 100 nm) and carbon particles with a high proportion of hydrocarbons, such as those found in Furnace Black (Black 2), to the overall behavior of carbon molecules. However, for the sake of precision, it should be noted that such particles are composed of thousands, if not tens of thousands, of molecules.

The retention of a grayish tone in the skin is particularly due to the properties of smaller carbon black particles and those with a high hydrocarbon content. The reasons for this include evasion from phagocytosis, appropriate pH levels, compatibility with the skin's lipid matrix, reduced immunogenicity, aggregation tendencies, and molecular stability. It should be emphasized that molecular stability is linked not solely to atomic structure but to the robustness of carbon bonds within the particles.

In conclusion, the phenomenon of brows "turning" gray can be primarily attributed to photodegradation discrepancies between carbon black colorants and other pigments in the formulation. However, the enduring grayish appearance is due to the inherent properties of smaller carbon black pigment particles and those with substantial hydrocarbon content.

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