How to Measure the Texture of Cosmetics: Powder and Gelled Products

The quality and appeal of cosmetic products are judged by factors such as texture, appearance, odor, and performance. Accurate and consistent analysis of texture provides manufacturers with vital information on the right combination of ingredients as well as the most suitable manufacturing methods to achieve the desired result. Texture analyzers (such as the TA.XTPlus Texture Analyser) can assess a wide range of cosmetic products at any stage of the production process and perform Texture Analysis tests to assess the physical parameters required to perfect a product.

Typical Texture Analysis Tests for Cosmetics Products

How to Measure Powder Flow, Cohesion, Caking and Speed Dependence

Powders represent a huge section of cosmetic products available on today’s shelves. These can be divided into two subcategories: loose or pressed. The user of loose powder – a bronzer, for instance – seeks to achieve even and consistent coverage on the skin. A satisfactory product will demonstrate the right levels of dispersibility and spreadability to achieve this coverage, using, for example, a brush.

The flow properties of a cosmetic powder will be an important factor in its maneouvreability around the factory, its successful formation into the end product, its transportation and storage and, above all, the consumer expectations of its use.

Powder Flow Analyser Controlled Flow Measurement technology offers you the ability to physically displace the powder in a controlled manner that can be optimized to measure the differences between samples, or can be adjusted to be complementary to your process conditions. The Powder Flow Analyser cuts through the sample as the axial force created by the test conditions is measured. Exponent software - intrinsic to the Texture Analyser - displays data in real-time, with subsequent data analysis providing insights into, for example, particle cohesion, batch variation and resistance to compaction. Depending upon the programmed rotation of the blade in terms of path angle, blade direction and tip speed the powder column can be displaced in a number of different ways to suit the process and properties to be measured. Test Settings can be optimized to show the maximum differentiation between similar products or to imitate the process or storage handling conditions, experienced by the product.

Manufacturers can assess and avoid typical problems such as batch and source variation of ingredients, caking during storage or transportation, and problems with discharging from hoppers or bins.

Powder Flow Analyser and patented precision rotor blade, the most important tool for powder flow measurement

How to Measure Compacted Powder Cake Strength

Compacted or pressed powders require enough cake strength to enable compression of the product into a tablet form and prevent it from flaking or dusting. This cake strength can be determined by means of a penetration test; attaching a cylindrical or needle probe to the TA.XTPlus Texture Analyser. Results from this test provide the mean force required to penetrate the sample within a given distance (e.g. 1mm). Test comparisons may highlight a need for weaker or stronger binding ingredients depending on the balance of characteristics desired; to the consumer, a satisfactory powder-to-cream eyeshadow is silky on the skin yet tacky in its container so as not to crumble or flake.

Assessment of hardness or ‘cake strength’ of eye shadows and typical comparative graphs

How to Measure Gel Strength, Rupture Force & Elasticity

Hydrogels are becoming a major influence in cosmetics today. There is a need for hydrophilic, skin adhesive, biocompatible hydrogels that can be used in a variety of cosmetic applications such as shampoo, hair setting gels, face masks, and skin fresheners. Currently, there are numerous hydrogels on the market, ranging from viscous solutions to elastic solids. The reason for this recent interest is that hydrogels can act as moisturizing agents and they can deliver numerous cosmetic ingredients in a controlled manner.

The physical properties of the hydrogels can be tailored to meet a variety of performance requirements. Gels can be made with varying levels of tack, gel strength, or mobility. Semi-fluid hydrogels can be formulated with active ingredients for cosmetics packaged in jars or tubes. Strong, immobile hydrogels can be formed on flexible film for facial masks, or between two layers of release films for cooling-gel products. The gels form a flexible film when dried, and they rapidly hydrate when in contact with fluids.

The measurement of gel strength is of widespread interest in the manufacture of cosmetic products. The strength of gels can also be utilized in products such as toothpaste, creams, and pastilles to modify the consistency of the required end product. Other gel properties such as gel elasticity and rupture force are also important textural characteristics.

The properties of a gel can be measured by the mechanical resistance to the stress of an aqueous gel of the material, of particular concentration. Using a cylinder probe (typically 0.5” or 1” radiused) the probe is lowered into the gelled system at a fixed rate to a distance of, for example, 15mm. The strength of the gel is assessed as the force to penetrate to a chosen depth prior to fracture. The rupture force is the force required to cause the failure of the gel and the depth at which this occurs indicates the elasticity of the gel.

A gel penetration test using a TA.XTplus Texture Analyser and typical graph

For a full summary of typical texture analysis tests that can be performed on cosmetic products:

Don’t Take Your Eyes Off the Quality

Today’s society does not tolerate imperfection. Manufacturers and developers of cosmetics must adopt a similar attitude when preparing their formulations. Stable Micro Systems offers a wider range of fixtures to accompany its market-leading and highly customisable texture analysers, presenting cosmetics manufacturers with the opportunity to produce perfectly textured products.

This information has been sourced, reviewed and adapted from materials provided by Stable Micro Systems Ltd.

For more information on this source, please visit Stable Micro Systems Ltd.