Ultimate Guide to Homogenizer Selection for Cosmetics Applications

The rise of self-care and wellness has fueled a surge in demand for innovative beauty products. Despite a temporary setback in 2020 due to the pandemic, the global cosmetics market has made a strong recovery and is on track to reach $132 billion by 2029¹, showcasing its resilience and impressive growth trajectory. Homogenization is essential for manufacturers in the cosmetics industry to craft high-quality products that truly stand out. Let's discover how selecting the right homogenizer can streamline your processes and elevate your products.

Benefits of Homogenization in the Cosmetics Industry.

Homogenization is the process of breaking down particles and evenly distributing them within a solution to create a stable, consistent mixture. In the world of cosmetics, this technique enhances product stability, uniformity, absorption, bioavailability, and overall effectiveness.

The effectiveness of cosmetic products, like beauty creams, largely depends on their ability to be absorbed into the skin. Homogenization drastically reduces particle size, which increases the surface area-to-volume ratio and enhances the absorption of active ingredients. This process not only improves the product's efficacy but also ensures efficient use of active agents, making formulations more cost-effective. 

The common substances in makeup include preservatives, thickeners and emollients.²

Take collagen, for example. Collagen is a vital protein that provides structure to the skin, hair, and nails, making it a sought-after ingredient in cosmetics and supplements. These products often promise smoother skin, fewer wrinkles, and improved hydration. However, collagen’s large molecular size poses a significant challenge, limiting its absorption through the skin or digestive system. This is where homogenization becomes a game-changer. During collagen production, homogenization breaks down large collagen fibers into smaller peptides, enhancing their solubility and bioavailability. These smaller peptides are more easily absorbed by the body, whether applied topically or ingested, making collagen products far more effective. Furthermore, homogenization improves the texture and consistency of cosmetic formulations, boosting their appeal to consumers. High-quality homogenizers are essential for producing collagen products that deliver on their promises of skin rejuvenation and hydration.

The benefits of homogenization extend beyond collagen. For example, it greatly improves the encapsulation and stability of active ingredients like vitamin E during spray drying. In one study³, Ultra-Turrax homogenization dispersed oil into maltodextrin and whey protein coatings, achieving a yield of 67.73% and an encapsulation efficiency of 73.73%. Adding a 7-minute ultrasonication step further increased encapsulation efficiency to an impressive 94.05% by producing smaller, more uniform droplets. This two-step process demonstrates a highly effective method for creating stable, vitamin E-enriched microcapsules, with exciting potential applications in the food industry.

While this article focuses primarily on the cosmetic industry, the value of homogenization is clear across multiple fields. It not only enhances bioavailability but also ensures product stability and quality, making it an indispensable tool for advancing innovation in both cosmetics and beyond.

Combining Ultra-Turrax and ultrasonic homogenization to achieve higher vitamin E encapsulation efficiency in spray drying.³

The cosmetics industry is constantly evolving, with a growing focus on developing safer, more natural products. As consumers become increasingly mindful of the ingredients in their skincare and beauty routines, the demand for formulations free from potentially harmful substances, such as parabens and alcohol, has surged.

Parabens are commonly used as preservatives, and alcohol acts as an astringent in many cosmetics. However, concerns about health risks have sparked debate. Parabens have been linked to hormonal disruptions, while alcohol can cause skin dryness and irritation. The challenge for manufacturers is to reduce these ingredients without affecting product quality or shelf life.

Advancements in homogenization technology are offering solutions. By achieving a finer and more uniform particle size distribution, products gain enhanced stability. The efficient mixing and emulsification processes also enable better integration of natural alternatives, providing a viable substitute for traditional parabens. Similarly, a more homogeneous blend reduces the reliance on alcohol as a solvent or astringent, paving the way for gentler formulations.

Key Factors to Consider in Homogenization.

1. Particle size distribution:

Particle size distribution (PSD) plays a critical role in industries like cosmetics, where precision and customization directly impact product performance. Advanced milling technologies now enable meticulous PSD control, resulting in brighter pigments, richer colors, and improved textures. These technologies also prioritize safety by reducing contamination risks, ensuring product purity and regulatory compliance. By tailoring PSD, manufacturers can enhance powder properties such as flowability, dissolution, and homogeneity, ultimately delivering superior functionality in cosmetic formulations.

Here are some key techniques used in particle and formulation engineering for cosmetics:

 - Milling is a common method for reducing larger particles into finer ones, widely used in the production of cosmetic products. Mechanical processes, such as pin milling and hammer milling, are utilized for coarse milling, breaking particles larger than 1mm into fine powders—typically under 100 microns. This process is essential for creating smooth, consistent formulations.  

 - Micronization is a highly effective technique for achieving precise particle size reduction and ensuring uniform particle distribution. Using specialized equipment, particles collide at high speeds under pressurized gas, such as compressed air or nitrogen, resulting in ultra-fine powders with homogeneous properties. This process enhances pigment brightness, color richness, and silky textures in cosmetics. Because the performance of micronization depends on the characteristics of the powders—such as flowability and strength—customizing the process is crucial for optimal results.  

 - Classification involves separating fine or coarse particles from a given particle size distribution. Using principles similar to those of jet milling, dynamic classifiers effectively isolate particles of significantly different sizes. This technique can remove agglomerates or non-micronizable particles from the final product, ensuring a consistent and refined formulation. It is particularly valuable for achieving precise particle size specifications and improving product quality.   

 - Spray drying is a versatile process that transforms liquid cosmetic formulations into fine, dry powders while maintaining uniform particle size and homogeneity. This technique offers several benefits, including enhanced product stability, extended shelf life, and improved preservation of active ingredients sensitive to moisture and temperature. By encapsulating volatile components like fragrances and oils, spray drying protects these ingredients until they are used by the consumer. Additionally, the process allows for controlled release of active ingredients, ensuring targeted delivery for greater product efficacy. 

2. Viscosity.

The physical form of a personal care product is one of the first things potential customers notice, alongside its color and fragrance. If the product is not easy to dispense or apply smoothly, it may deter customers from making a purchase—or coming back for more. Even the way a product flows within its packaging can influence their perception. Measuring this characteristic is also crucial for ensuring consistency and reproducibility across your products. While often referred to as viscosity, the precise scientific term is rheology, which encompasses much more than just viscosity alone.

The property of “viscosity” provides insight into the thickness of a material and its ability to flow. Scientifically, viscosity is defined as the measure of a fluid's internal resistance to flow. For example, when comparing a high-viscosity material, such as hair gel, with a low-viscosity material like body wash at the same temperature, the higher-viscosity material flows more slowly.

Simple viscosity measurement.⁴

Viscosity is affected by environmental factors like temperature and pressure. While any change in temperature impacts a material's viscosity, the degree of this effect varies depending on the fluid. For instance, some fluids can experience a 10% shift in viscosity with just a 1°C change in temperature. In contrast, pressure has a less pronounced effect on viscosity. However, substantial pressure changes—such as an increase from 0.1 MPa to 30 MPa—can result in a similar 10% change in viscosity for most liquids.

Viscosity is influenced not only by environmental conditions but also by external processes like pouring and pumping, as well as the material's internal structure, such as molecular shape and arrangement. To replicate external forces, rotational viscometers are frequently used, allowing precise adjustments to the speed of rotation. Additionally, the length of time a material is subjected to external forces can significantly impact its viscosity.

Liquid make-up exhibits a range of rheological properties to meet consumer demands. Manufacturers must carefully control the yield point, which determines the force required to dispense the product from its tube. Additionally, the liquid must display thixotropic behavior, allowing its viscosity to recover after being dispensed. This prevents the product from dripping off a finger or application brush. Moreover, the make-up should demonstrate shear-thinning behavior to ensure it spreads smoothly and evenly across the skin.

A simple and effective way to ensure the quality of liquid make-up is through the use of a rotational viscometer. To analyze both shear-thinning behavior and the yield point simultaneously, a shear rate ramp can be performed using DIN spindles in accordance with ISO 3219⁵ or DIN 53019⁶. The measurement process involves starting at a low rotational speed and gradually increasing to a higher speed (e.g., from 10 rpm to 100 rpm), collecting data points along the way.

The yield point is then calculated using mathematical regression models such as Bingham, Casson, or Herschel-Bulkley. The model that best fits the data curve should be selected for accurate analysis of the yield point.

Flow curve diagram and yield point determination of liquid make-up using the Herschel-Bulkley regression model.⁷

Homogenizer selection for Viscous Materials.

Homogenizing viscous materials can be challenging due to their resistance to mixing. The effectiveness of homogenization largely depends on the type of homogenizer used and the sample's viscosity.

• Rotor-Stator Homogenizers: Effective up to 10,000 cP but efficiency declines with higher viscosities. Using deflector heads or moving the rotor-stator can improve mixing.

• Ultrasonic Homogenizers: Work better with viscous materials than rotor-stators but have limitations. If the sample is too thick to pour, it cannot be effectively sonicated.

• Bead Mill Homogenizers: Limited suitability for viscous materials, as beads can't move freely in thick samples.

• High-Pressure Homogenizers: Depend on the sample’s ability to flow through narrow slits, making them better suited for less viscous materials.

Homogenizing viscous samples can be challenging, but there are effective strategies to improve the process without compromising performance. One key approach is to take advantage of the fact that a material's viscosity decreases as its temperature rises. Conducting homogenization at higher temperatures generally results in better mixing. However, it is crucial to verify the decomposition temperature of your material beforehand to ensure it remains intact during the process.

An effective approach to adjusting viscosity involves the use of surfactants or emulsifiers. These agents reduce internal resistance within the material, enabling it to flow more easily and decreasing its viscosity, while certain emulsifiers may also increase viscosity. By selecting the appropriate rheology modifier, it is possible to improve homogenization while preserving both efficiency and the integrity of the sample.

Rheology Modifiers for Cosmetic Formulations ⁸

Achieving the desired viscosity and flow behavior in cosmetic formulations requires careful selection of ingredients with specific rheological properties. Additionally, a wide range of formulation additives, known as rheology modifiers, can be used to fine-tune these properties. Some key categories of rheology modifiers include: 

Mineral Colloidal Systems: Minerals (naturally sourced) such as Magnesium Aluminum Silicate, Bentonite, and Hectorite can be used to create colloidal systems which impart viscosity in a non-Newtonian manner. Typically synergistic when used with gums (xanthan).  They also have a smooth, ‘dry’ feel. Hydrophobically modified minerals can also provide rheology modification in non-aqueous systems.

Polymeric Thickeners: These, usually acrylate based polymer thickeners, are cost effective and efficient at low use levels, can provide suspension of particles but can be sensitive to salt content and tend to short, choppy rheology.

Cellulosic Thickeners: Based on cellulose (wood pulp), these synthetically modified polymers are similar to the polymeric thickeners in that they can be highly efficient.  At higher use levels they can feel slippery or stringy and do not provide suspending properties.  Hydrophobic modification can allow for use in solvent systems.

Associative Thickeners: These thickeners interact with surfactants in a way that moderates flow and adds viscosity.  They can be sensitive to different ingredients including sulfate free surfactants.

3. Miscible vs. Immiscible Materials.

Some mixing processes involve straightforward blending of compatible liquids, such as incorporating color solutions into miscible bases or combining oils, alcohol, and water in perfumes and colognes. This type of mixing, known as simple blending, is the most basic operation in cosmetic manufacturing. It is typically achieved by creating bulk flow throughout the mixing vessel.

In contrast, more complex processes, such as forming emulsions from immiscible liquids, suspending gelling agents, or dispersing pigment agglomerates in viscous liquids, require a different approach. Creating an oil and water emulsion requires specialized equipment, such as a homogenizer. Initially, the emulsion forms a uniform, homogenous mixture. However, over time—typically between six months to a year—this mixture can lose its stability and separate back into two distinct, immiscible layers. There are techniques to maintain emulsion stability and ensure a high-quality final product.

Emulsions, which come in oil-in-water (o/w) and water-in-oil (w/o) forms, rely on powerful mixing methods and surfactants for stability. Since oil and water are naturally immiscible, homogenization is often used to apply mechanical forces that effectively blend particles. Surfactants play a key role by dispersing particles into micelles, with their selection determining whether an o/w or w/o emulsion is formed, as well as the stability of the product. A stable emulsion depends on two key factors: optimized surfactant formulations, which break up and stabilize droplets (often using multiple surfactants in o/w emulsions), and high shear mechanical forces, such as those from high-pressure homogenizers. These forces overcome the resistance of particle chemistries and create finely dispersed, long-lasting emulsions, aided further by impact, cavitation, and adjustable intensity in high-quality equipment. Systems like the Nano DeBEE or NanoGenizer-Ⅱ are particularly well-suited for this type of homogenization.

The initial step in creating a water-in-oil (w/o) or oil-in-water (o/w) emulsion is investing in equipment designed to deliver a consistent and finely controlled particle size distribution. Emulsion production typically relies on high-pressure mixing, with homogenization being the preferred method. This approach is favored for its superior ability to achieve significantly smaller particle sizes compared to other blending or emulsification techniques. 

Homogenizing powders into liquids.

Solid-liquid mixing involves finely dispersing insoluble solids into a liquid feed to create a stable suspension. The stability of the mixture improves with smaller, more uniform particle sizes. For instance, in the production of a final product, a base cream acts as the liquid foundation. By evenly incorporating finely ground solids into the base, a smooth, pasty consistency is achieved.

Incorporating powders into liquids often presents the same persistent challenges with traditional methods: clumping, undissolved residues, and powder build-up on unwetted tank surfaces and mixing tools. These issues lead to prolonged processing times and potential quality inconsistencies, ultimately reducing both productivity and the reliability of the system. Inline dispersers embody cutting-edge technology, designed to efficiently create both solid-liquid and liquid-liquid mixtures with precision and ease.

Homogenization Quality Standards in the Cosmetics Industry.

Each category of cosmetics follows specific quality standards to ensure safety, effectiveness, and customer satisfaction.  When it comes to cosmetic products that require homogenization, there are certain factors to consider when choosing the right homogenizer for the job.

The quality standards for cosmetics depend on the specific characteristics of the product being processed. Here are three examples illustrating how these standards apply to various cosmetic products.

Creams and lotions.

These products require precise blending to ensure an even distribution of pigments and active ingredients, which is essential for both their effectiveness and visual appeal. Eliminating air bubbles is equally important, as they can compromise the texture, stability, and overall performance of the product. High shear mixers provide an energy-efficient solution for processes that do not demand significant particle size reduction, making them ideal for low-shear applications. However, when achieving finer particle sizes and superior uniformity is critical, homogenizers become the optimal choice. The right homogenizer depends on the type of cream or lotion being produced. For example, Rotor-Stator Homogenizers are a great choice for standard creams and lotions. On the other hand, Ultrasonic Homogenizers are ideal for serums and sensitive skin products, as they provide gentle processing with minimal heat, ensuring delicate formulations remain intact.

Powders. 

Whether it is face powders, eyeshadows, or blushes, maintaining uniform particle size is essential to ensure smooth application and prevent patchy results. Precision in formulation is also key to avoiding clumping, which can compromise the product's usability and visual finish. In the powders cosmetics industry, different techniques are used along with homogenization.

Particle size distribution and uniformity are key for cosmetic powders, with micronization being the key technique to enhance product quality. It can be applied to formulations or individual ingredients, offering benefits like improved color intensity, stability, dispersion, and application. For example, smaller particles create vibrant colors, better UV protection (e.g., micronized titanium dioxide), smoother textures, and softer, more natural finishes. This process also enhances product performance by preventing settling and ensuring easier mixing into liquids or creams.

High pressure homogenization is viewed as a wet micronization technique capable of achieving micron and sub-micron particle sizes.

Comparison of Traditional Micronization⁹

Spray drying technology provides effective solutions for powders challenges. Spray drying converts liquid cosmetic formulations into fine, dry powders, ensuring uniform particle distribution and enhanced product homogeneity.

A key advantage of spray drying in cosmetics is the improved stability it offers. Active ingredients, often sensitive to moisture and temperature, are better protected in powder form, minimizing degradation and extending their effectiveness over time.

Additionally, spray drying enables the controlled release of active ingredients, enhancing product efficacy by delivering them in a more precise and targeted manner. The technique also facilitates the encapsulation of fragrances and oils, safeguarding these volatile components until they are utilized by the consumer.

Lipsticks and Balms.

Lipsticks are formulated by dispersing pigments into a carefully selected blend of oils and waxes. The choice of pigments and raw materials is strictly regulated by organizations such as the EU and FDA to ensure consumer safety. Commonly used oils include castor oil, mineral oil, and petrolatum, while structural integrity is provided by waxes such as beeswax, carnauba, candelilla, and ozokerite (also known as ceresin). These waxes may be incorporated in various forms, including powders, flakes, pellets, or solids. Additionally, silicone compounds are occasionally added to enhance the overall formulation.

Other key ingredients include emollients for hydration, dispersants to evenly distribute pigments, preservatives for longevity, and fragrances for appeal. Some lipsticks also offer added benefits, such as UV protection or a pearlescent finish. The typical composition of a lipstick base consists of 50-70% oil, 20-30% wax, and 5-15% pigment.

Lip balms, or salves, are formulated similarly but replace pigments with moisturizing agents, sunscreen, or active ingredients like camphor to provide additional skincare benefits.

Lipsticks are usually made in small batches following a standard process. First, oil is heated to 175–185℉ (80–85℃), while waxes are melted in a jacketed vessel (or “kettle”) with a stirrer and scraper, with some oil added to assist. The melted wax and oil are then blended using mixers or dispersers. Powdered pigment is dispersed in oil to create a “pigment grind,” often using a triple roll mill or bead mill, though pre-micronized pigments—which do not require grinding—are becoming popular but may still need shearing to break agglomerates. Liquid pigment dispersions, which are more expensive, are also widely used and are mixed into the oil/wax phase until smooth, sometimes passing through a colloid mill. The pigment grind is then mixed into the oil/wax phase and processed thoroughly. The mixture is cooled slightly before fragrances, preservatives, and other ingredients are added. Finally, the product is poured into molds and cooled to solidify, with the lipstick sticks often “flamed” afterward to create a glossy finish.

Using a rotor/stator homogenizer to prepare the premix can improve product quality and consistency. It offers benefits such as better product texture, and a more uniform premix with smaller particle size, all contributing to faster production.

A set of lipstick in various colors.

Scaling Up Cosmetic Production 

Scaling production is not as simple as increasing ingredient amounts. Ingredients used in cosmetics and skincare can behave unpredictably in larger volumes. For example, plant-based ingredients, preservatives, and electrolytes may react differently during large-scale mixing.  

Mixing dynamics also change when scaling from lab to production due to differences in vessel size, heating, and cooling. Larger vessels take longer to mix, heat, and cool, which can affect the product.  

Replicating lab stability on an industrial scale is challenging. Industrial machinery often can not match the shear and force of lab equipment, making scaling difficult for many labs and companies.

Scaling up a homogenization process from a smaller, lower-power system to a larger, higher-power one can require some trial and error to achieve comparable performance. For instance, a smaller ultrasonic homogenization system using a small probe and high amplitude for processing small volumes may not directly translate to a larger system with a bigger probe and lower amplitude for larger volumes. To ensure a smooth transition, it is crucial to review the manufacturer’s specifications before scaling up.

Ultrasonic homogenizers provide a useful example. When reviewing the specifications of various probes for a specific ultrasonic homogenizer model, it becomes evident that each probe has a designated maximum amplitude. Notably, as the probe size increases, the maximum amplitude generally decreases. This occurs because larger probes require more energy to operate effectively.

Understanding amplitude settings in ultrasonic homogenizer systems is essential. Rather than setting an exact amplitude, you typically select a target percentage of the system's maximum amplitude. However, when working with highly viscous materials, reaching the maximum amplitude may not be feasible due to increased resistance. For more information, visit Scaling Up an Ultrasonic Homogenization Process.

Scaling up a rotor-stator homogenization process can be complex, with factors like viscosity, particle size, emulsion stability, and texture impacting product quality. Common challenges include inconsistencies, phase separation, and inefficiencies, which can increase costs and time. To ensure a successful scaleup, focus on key factors such as production equipment, vessel size and shape, homogenizer positioning, power and flow dynamics, and shear forces. By addressing these, you can achieve efficient, consistent results for emulsions, suspensions, and other formulations. To learn more, refer to the guide on Scaling Up a Rotor-Stator Homogenization Process.

High-pressure homogenization utilizes a range of forces to break down particles: shear, cavitation, and impact. Most high pressure homogenizers utilize a flow-through design in contrast to the often batch design of most laboratory-scale homogenizers. Because of these differences in design, high pressure homogenization processes scale more directly than do most batch homogenization processes. The key settings, such as pressure, and system configurations used in smaller scale high pressure homogenization systems can often be directly scaled up to larger systems, which is almost never the case with batch systems., .

The Nano DeBEE High Pressure Homogenizer, for example, offers seamless scalability to larger DeBEE systems, making it an excellent choice for larger-scale production. It enables an easy transition from small volumes of 12-15 ml to higher capacities of 2 or 4 liters per hour, depending on the model. Its versatility ensures efficiency and adaptability in various production settings. Brands like Pion provide a range of laboratory and industrial homogenizers to meet diverse scale-up needs.

Here are key considerations to keep in mind:

• Particle size: Knowing the desired particle size for your product is key to choosing the right mixer type, size, power, and configuration for production. Defining your target size can help avoid overspending on overly powerful equipment. Testing particle size is also essential to ensure consistency between lab batches and scaled production. Consider using a laser diffraction analyzer for accurate measurements.

• Rheology: The rheological properties of your lab-produced product—defining how it flows and deforms under stress over time—are critical data points for designing an appropriate mixing system for large-scale production. This is particularly true for cosmetic, skincare, and personal care products, which often incorporate modifiers such as thickeners and texturants, or include active ingredients and botanicals. These additions can introduce complexities in consistently maintaining desired characteristics such as skin feel, handling, and stability at higher production volumes.

• Heating and cooling times can vary significantly between a small five-pound lab batch, a 50-pound pilot batch, and a 500-pound production batch. These variations may influence the desired characteristics of your product, requiring adjustments to the heating and cooling profiles for larger batch sizes to ensure they meet product specifications.

• Ingredient application will change from lab to production floor. Since adding a pound of a seed butter ingredient in a lab mixer is much easier than adding a 100-pound block of the same ingredient into a production mixing vessel, you must carefully consider the additional ingredient processing steps (cutting, pre-mixing or specialized loading) that must be used in production. Additionally, changing the order of how ingredients are added to the larger production batch may impact the characteristics of the final product.

• pH levels play a vital role in the formulation of cosmetic, skincare, and personal care products. Levels that are too low or too high can significantly affect a product’s safety, efficacy, color, and other critical characteristics. Therefore, it is essential to closely monitor and adjust pH levels throughout every stage of production, particularly when scaling up to larger batch sizes.

• If pre-mix vessels are used, they can impact both scaling and ongoing production operations. Some cosmetic and personal care products processors deploy a series of smaller vessels to pre-mix key components of their formulations. For example, they might use one pre-mix vessel for mixing color ingredients and another for mixing fragrances, before adding those components to the main oil/water emulsion base in the main vessel. This approach can allow for each premix to be closely monitored and tested for consistency and other characteristics before the final mixing process.

Selecting the appropriate homogenizer is essential for success in the rapidly evolving cosmetics industry. The capability to produce stable, uniform, and high-quality formulations not only enhances product performance but also aligns with the increasing consumer demand for safer, more effective beauty solutions. Investing in advanced homogenization technology enables manufacturers to optimize production processes, elevate product quality, and maintain a leading position in the dynamic cosmetics landscape. For additional information on the characteristics of homogenizers, please refer to: Choosing a Homogenizer Technology for Your Application.

References:

1. https://www.statista.com/topics/3137/cosmetics-industry/ 

2. https://letstalkscience.ca/educational-resources/stem-explained/chemistry-lipstick 

3. https://www.sciencedirect.com/science/article/abs/pii/S1674200124001792 

4. https://wiki.anton-paar.com/be-en/viscosity-measurement-in-the-personal-care-industry/  

5. https://cdn.standards.iteh.ai/samples/8426/05b46c6c407e46deae708fa7e16bd9b3/ISO-3219-1993.pdf 

6. https://webstore.ansi.org/standards/DIN/din530192008

7. https://wiki.anton-paar.com/en/viscosity-measurement-in-the-personal-care-industry

8. https://www.scconline.org/Education/Blog/Viscosity-Rheology-and-Rheology-Modifiers  

9. https://www.jetmillmfg.com/the-ultimate-guide-to-micronization/#High_Pressure_Homogenize