TESTING
Measuring properties of human hair surfaces
Mark Cresswell - Lucideon
Valuable information obtained from the surface characterisation of hair fibres can deliver important insights into the performance of hair care products. These insights are often utilised in the development of product formulations due to the deepened understanding of the connection between product use and the resulting surface properties of the treated hair fibres. Modern hair care products include a wide
range of shampoos, conditioners, styling products, and colourants. The chemistry of each product is complex and formulated to bring a specific cosmetic or medical effect, e.g. cleansing, anti-dandruff, shine, lustre, and thickening. For example, a proprietary shampoo
may contain cleansing agents (surfactants), conditioners, functional additives, preservatives, aesthetic additives, and medically active ingredients. To obtain regulatory approval, or to substantiate product claims, it is essential to be able to measure the exact effect a given product will exert on hair properties. A vast range of relevant hair properties can
be determined through the use of topographical and chemical surface characterisation techniques. Non-contact white light interferometry (WLI) and 3D scanning electron microscopy (3D SEM) are used to investigate topographical consequences such as scale height and hair damage. These techniques provide statistically based metrology of hair surfaces either parametrically or as quantified 3D images. In addition, chemical surface analysis
techniques such as X-ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectrometry (SIMS) can be used to determine chemical residues and natural substrates in terms of material identification, quantification, and spatial distribution. Increasingly, the development of effective
hair treatments relies on a detailed knowledge of the surface chemistry of the hair and the effect of the various ingredients of the formulation on hair structure, e.g. the effects of additives on the surface lipid structure is one area of ongoing investigation. At Lucideon, our experience in applying
these analytical techniques to product development projects allows us to translate complex data into actionable insights for product formulators. Combining advanced surface characterisation and imaging technologies with our knowledge of consumer
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product performance allows us to help brands optimise the performance of their hair care products and guide the development of marketing material that can improve consumer trust.
Chemical properties of hair The structure of hair is intimately linked to its chemistry, which is what imparts its particular physical properties and characteristics. Hair is an outgrowth of the epidermal region of the skin, comprising the hair follicle and the hair shaft. New cells are continuously produced in the lower portion of the hair bulb and push the previously formed cells upwards.
As cells reach the upper portion of the
bulb, they begin to change into six cylindrical layers. Melanocytes in the hair bulb produce the melanin pigment that gives hair its colouration. The structure and chemistry of these hair features can be explored through extraction, drying, and surface analysis using SEM (Scanning Electron Microscopy) and mass spectrometry - specifically ToFSIMS (Time-of- Flight Secondary Ion Mass Spectrometry). In the mid-follicle region, the growing
cells die, harden, and form the hair, which is a mixture of hair proteins such as keratin. These proteins and protective fatty acid esters on the hair surface can be characterised analytically to monitor the effects of hair treatments and damage.
The most abundant surface lipid on human
hair, 18-methyl eicasanoic acid (18-MEA) can be readily detected using ToFSIMS from which its relative surface levels can be directly related to the surface treatment(s) applied. 18-MEA is the only covalently bound surface
Figure 1: Scanning electron microscope (SEM) image of human hair
lipid, the level of which is related to the gloss/ sheen of hair, and its removal during, say, bleaching processes can be duly measured. Some consumer healthcare companies are looking to protect hair by derivatising lipids in situ during hair treatment or by depositing them directly from treatment formulations. The hair shaft comprises dead cells and
November 2025 PERSONAL CARE
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