Formulation: Raw Material Types and Testing

Formulation: Raw Material Types and Testing
Cosmetic products generally consist of powder blends, think of foundations, eyeshadows, primers, blushes, bronzers etcetera.

Many of these powders consist of pigments. Pigments can be further classified into subsets such as inorganic pigments and oxides of various kinds. Since almost all cosmetics consist of blends, it makes formulation one of the most important facets of the cosmetics industry.

Powder formulating can only come about through (often many years of) research, experimentation, testing, and development, making it as much a science as it is an art, making use of a wide range of materials and techniques.

Pigments and powder formulating

Cosmetic products consist of powder blends (pressed or as loose powders) such as eyeshadows, primers, blushes, and foundations. Powder formulations come about by the mixing of pigments, fillers, dry as well as wet binding agents with the intent to develop and produce a consistent product based on specific requirements. 

When developing a blend there are many types of raw materials that are being worked with: iron oxides, titanium dioxide, chromium dioxides, zinc oxide. When dealing with these raw materials to make a cosmetics product formulation, processing techniques and the material’s physical characteristics and properties are important factors.

Mixing

Aspects as powder flow, homogeneity, selecting the correct powder mixer based on the materials’ properties, such as particle size and shape, density, and the content of each component added to the mixture, as well as taking the mixer fill volume, mixing duration, and the number of revolutions and speed into account, all minimizes the possibility of segregation.

Segregation

Various types of material segregation may occur, these types of segregation are sifting segregation, fluidization segregation, and trajectory segregation.

Sifting segregation

Sifting occurs when there is a substantial difference in particle size (diameter) in a mixture. The relative movement of particles causes the smaller particles to sift through the coarser material. Besides, also a different (dynamic) angle of repose may induce separation of particles based on their size and interaction. 

Fluidization segregation

Fluidization generally occurs during unit operations such as material transfers from one part of the process to the other by e.g. pneumatic transport, but is can also occur during discharge for example, when a large mixer or hopper is emptied and air is entrained.

Trajectory segregation

Finer particles in a blend typically have less momentum in the course of movement by e.g. vibrations as compated to larger and heavier particles. Accordingly, the larger particles move further away from the discharge point whereas the smaller particles stay closer to the discharge point.

Useful reading

During the mixing of cosmetics various phenomena may occur. Delft Solids Solutions has produced a great deal of content in regards to these subjects.

Below you will find an article list per subject

Segregation
Segregation testing of powders and solids

Flow problems
Consolidated flow and Ring Shear Testing
Unconfined powder flow testing

Stickiness
Powder stickiness measurement

Agglomeration
Granulation and size enlargement

Mixing
Product development by powder mixing

How material physical properties determine the appearance and effect of the product.

A cosmetic foundation provides even coverage, which is used as a base for the appliance of other highlighting and finishing powders such as rouge and powder blushers to provide specific appearances by reflecting light in specific colors or diffusing light evenly over the skin surface. Facial powders most commonly include iron oxides, zinc oxides, and titanium dioxide.

In addition to appearance improvement, face powders can also provide sunscreen protection with the inclusion of strong light scattering components such as zinc oxide and titanium dioxide. The particle size distribution of these components affects the appearance and stability of the product.

Different effects can be achieved by the right choice of pigment and particle size. Small particles (less than 15 microns) create silky and satin effects and will opacify the mass. Larger-sized particles (larger than 100 microns) create high luster effects, either sparkling or glittering, combined with high brilliance and transparency.  

Measuring Pigments with Laser Diffraction for Particle Size Analysis

Particle size and shape are critical physical characteristics of pigments as we have illustrated in the previous section. Delft Solids Solutions offers Laser Diffraction and Static Image Analysis as methods for particle size and shape assessment, allowing for accurate data useful in quality control and product development and optimization, as well as offering a clear operational view to meet product performance criteria.

Electron microscopy for the detection of impurities

For manufacturers in cosmetics, aside from everything already mentioned, the purity of the raw material is very important, i.e. identifying contaminants (small amounts of contaminating particles) and their origin. This helps to ensure product quality and prevents process and product deficiencies.

The scanning electron microscope (SEM) is often used when a more detailed visualization of a solid material is necessary. Approximate particle size and more detailed shape, and topographical information can be obtained. Including EDX (Energy Dispersive X-ray) in the microscope assists in determining microscopically-sized contaminants.

Challenge or query?

We always aim to test material under conditions that best match or as closely as possible resemble the practical application and process conditions of the material, this includes temperature and humidity.

Material characterization analysis allows us to help the (bulk) solids industries to meet regulations and maintain a constant level of product consistency. Using physical characterization and testing data is essential in maintaining expected levels of operation in terms of product quality, properties, and performance.

These are several materials we have tested for the cosmetics industry.

  • Aluminum oxide
  • Butyloctyl salicylate
  • Dimethicone
  • Iron oxide
  • Kaolin
  • Liposomes
  • Mica
  • Palmitate
  • Stearic acid
  • Talc
  • Titanium dioxide
  • Zinc oxide

Please feel free to contact us for advice and/or brainstorming. We are always happy to connect with our peers.

Are you facing challenges, want to resolve issues, or need a second opinion, or want to brainstorm, please feel free to reach out to us at any time by clicking here.

This article is published by

Delft Solids Solutions is a privately-held contract research organization working on research and characterization of solid materials. Topics include, but are not limited to, primary physical properties as porosity, pore volume, pore size, surface area, particle size, density of powders and granules. We also investigate related characteristics such ...

https://www.solids-solutions.com/rd/materials-development/pneumatic-transport/