The cosmetics and personal care market is extremely crowded with new product introductions making it an extremely competitive arena. In this industry, the combination of good marketing and product quality must be compelling to gain shelf space, consumer attention, and repeat purchase.
Today, differently formulated cosmetics use several thousand ingredients, both natural and synthetic. New ingredients come about frequently and the real usefulness of each is determined by evaluating a material compared to similar materials already on the market. The designer is faced with the challenging task of developing new aesthetically appealing formulations that deliver functional properties – such as cleansing, conditioning, skin moisturization, viscosity, and mildness – at a price affordable to the consumer.
Increased attention has been focused on the Cosmetics and Skincare Testing to improve their performance and to fulfill the requirements in legislation demanding proof of certain product claims. Advances in cosmetics tend to be a succession of small improvements; companies often need to start at an early stage of product development to evaluate products for verifiable changes and need carefully conducted experiments in order to provide definite information. Likewise, it is important to obtain knowledge about competitors' products and to achieve competitive advantages.
Information about product performance can be obtained by the use of Texture Analysis, which can play a pivotal role in measuring product conformity and compliance with standards as well as analyzing and controlling the desired textural features of any new or existing product for the market.
Analysis of the way in which different types of cosmetics respond to the tests provides the manufacturer with vital information: which combination of ingredients is the ideal for a particular product; which processing methods/times produce the best results; and whether the quality is consistent.
Typical Texture Analysis Tests for Cosmetics Products
How to Measure Lipstick Hardness/Bending Force
Inconsistencies in lipstick formulations are perhaps more noticeable than in any other cosmetic product. Colorants must be uniformly and completely dispersed to avoid a grainy product. Lipsticks are expected to be easily applicable and not bend, crack, or break during application and must also look glossy and visually appealing. The TA.XTPlus Texture Analyser can be used to assess these physical properties and consequently, formulations can be adjusted to prevent problems such as excessive stickiness, hardness, or brittleness.
Lipstick hardness can be determined by means of a penetration test. When the test probe comes into contact with hard particles or air pockets, resulting from either incomplete colorant dispersion or the working and chilling process, inconsistencies are displayed as fluctuations in force.
Rigidity is another key property. Lipstick must be rigid enough to withstand firm application to the lips. In this instance, a cantilever rig can be attached to the Texture Analyser to test the force required to break the lipstick in two.
Comparison of lipstick/lip balm hardness using a penetration test and typical comparative graphs
Comparison of lipstick resilience using a cantilever test and typical comparative graphs
How to Measure Pencil Hardness/Rigidity
Similar rigidity or hardness tests can be carried out using specialized fixtures on lip and eye pencils, again providing valuable information on the product’s usability and the potential need for formulation or manufacturing adjustments.
The core of a pencil should be hard enough to leave a defined line on the skin without scratching and should withstand sharpening. At the same time, the pencil should be soft enough to allow a smooth application. The texture on the application is not the only factor in the formulation of these products. Product developers also need to consider environmental factors such as temperature and shelf-life of the product in formulations.
Assessment of eye pencil rigidity using the Eye Pencil Rig and typical comparative graphs
How to Measure Wax Hardness/Stickiness
The beauty of waxes is that they achieve hold yet are flexible; the perfect combination for hair styling. Wax is not water-soluble thus not prone to drying. What waxes do risk however is becoming too greasy, heavy, or sticky – properties that may be undesirable for hair products yet, on the other hand, desirable for other applications. In either case, there is a requirement to measure these properties in order to control and monitor them. There are two measurements to be taken into account when achieving the desired texture of a wax: hardness and stickiness.
It is the so-called work of adhesion that is responsible for the bonding effect of wax. In texture analysis terms, this means the amount of energy required to separate the wax from the test probe in an adhesion test. In such a test, a cylinder or spherical probe is applied to the surface of wax and then withdrawn after a few seconds of contact. On withdrawal of the probe from the surface of the wax, a softer, more supple wax will take less force than a strong, sticky wax to retract the probe. Graphically, the stickiness of a sample is represented as the peak in the force curve. Peelability tests of wax strips, which will be a function of stickiness, can also be assessed via texture analysis.
Assessment of wax stickiness using a hemispherical probe and typical comparative graphs
How to Measure Cream Consistency
When formulating products such as moisturizing creams and lotions the materials to be used will depend largely upon the required end product consistency. A thin lotion for easy pouring will require the addition of different ingredients or quantities than that required for a thick cream. A product developer may wish to create a product that squeezes out of a tube and breaks sharply after squeezing. These consistencies can be assessed by either a forward extrusion test (simulating the force required to extrude the sample by the consumer) or a backward extrusion test, which will give an indication of product physical failure and viscosity. Backward extrusion tests are often preferred as the product may be tested directly from the container in which it was originally dispensed thereby avoiding disruption of the sample and potential changes of properties prior to testing.
Consistency assessment of lotions and creams using forward and backward extrusion tests and typical comparative graphs
For a full summary of typical texture analysis tests that can be performed on cosmetic 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.