Comparing touch senses of naïve and expert panels through treated hair swatches: which associated wordings correlate with hair physical properties?

OBJECTIVES: This study (i) compared the sense of touch between a naïve and expert panels, under visual or blind conditions, using differently treated hair swatches and (ii) explored possible common wordings used by both panels and their possible links with some physical properties of hairs. METHODS: Two sets of 15 hair swatches of Caucasian and Chinese origins were differently treated (bleached, permed, brushed, etc.) or organized (root-tip vs. tip-root). These were evaluated by tactile assessments by two panels (105 naïve consumers and 10 hair experts) under visual or blind conditions, in two geographical locations. A series of 17 defined antonym adjectives, as descriptors, allowed responses of each panel to being scored and their preference mappings to being defined on a like-dislike scale. Hair swatches were measured and assessed by various instrumental techniques (bending, diameter, cuticle cohesion, alignments of hair). RESULTS: Apart from a few overlaps, all 15 hair swatches were well differentiated by both panels which showed a global agreement, making experts reliable assessors. Only three descriptors among 17 correlated with some objective measurements. Tactile-visual assessments differ from those performed tactile blind in both panels. Agreements between both panels appear, however, closer under tactile-blind conditions. CONCLUSION: Trained hair experts were confirmed as reliable representatives of a larger and naïve cohort, viewed as consumers. Hair swatches were well differentiated by both panels, with comparable descriptor rankings.

Particulate matter adheres to human hair exposed to severe aerial pollution: consequences for certain hair surface properties.

BACKGROUND: The deposit and adherence of particulate matter (PM) from aerial pollution onto the surface of human hair is a poorly studied phenomenon. OBJECTIVES: (i) To reproduce in vitro the deposit of known PM on standardized hair swatches in a closed box, (ii) to compare in vitro data with those obtained under 'real-life' conditions of severe aerial pollution and (iii) to assess the changes of the hair surface properties, potentially caused by the adherence of airborne PM onto the hair. METHODS: In vitro: a PM was sprayed onto untreated or sebum-coated hair swatches. Real-life conditions: other swatches were exposed to a severely polluted environment, for 24 to 72 h, in Baoding (PR China). In both cases, swatches were examined using scanning electron microscopy. The shine, the frictional properties and the level of metals were measured and compared to those same properties for the unexposed swatches. RESULTS: This work clearly indicates that, under real-life conditions, a large number of PM of various sizes are deposited onto the hair surface. This phenomenon is increased by the presence of sebum and longer exposure times. The in vitro level of PM deposited onto the hair surface is comparable to the in vivo level. The presence of sebum seems to favour the deposit of larger PM. The shine of the exposed swatches is significantly decreased, whereas their respective friction coefficients are significantly increased. Both the presence of sebum and length of exposure time increased the amount of analysed metals present on the exposed hair surface (Al, Fe, Cu, Ba and Zn). CONCLUSION: This work indicates that a very high amount (e.g. billions) of PM can be deposited on a full head of hair for subjects living in a severely aerially polluted environment. This process can be reproduced in vitro. In real-life, pollution has a strong impact on hair surface properties, leading to a modification of the visual aspect (loss of shine) and the alteration of hair surface (increase in friction force). This work may be used to pave the way for prevention and cleansing studies in the field of hair care.

What is a Caucasian 'fine' hair? Comparing instrumental measurements, self-perceptions and assessments from hair experts.

OBJECTIVE: To determine the various factors contributing to what Caucasian women describe as 'fine hair'. METHODS: Three complementary approaches were used, namely self-evaluation by the volunteer, assessment by a sensorial expert and instrumental measurements, in order to determine some of the possible parameters taken into account by Caucasian women when they describe the notion of fine hair. One hundred fifty one women of Caucasian origin participated in the study. They varied in age, and varied in that some considered themselves as having fine hair, and others not. The instrumental measurements carried out included hair diameter measurements, hair density measurements, hair breakage force, hair flexibility and scalp sebum levels. RESULTS: From six parameters defined initially, four parameters were found to be in common with the three approaches: hair abundance (density), hair thickness, hair resistance and the volume of the hair on the head. The commonly used term 'body' was only common to self and expert evaluation, whereas the influence of curliness was only common to expert evaluation and instrumental measurements. CONCLUSIONS: This study has shown close agreement between sensorial and instrumental findings, and also illustrates how the women participating can subtly and adequately describe their own hair. It is important to note that the words 'fine hair' describes a lot more than just physically thin hair fibres. Ageing is an additional factor that clearly impacts certain parameters associated with 'fine hair' among the volunteers.

Analysing the movement of a hair swatch using video and image analysis: a promising technique for exploring the dynamic properties of hair.

OBJECTIVE: The aim of this paper is to present a new instrumental evaluation method of hair movement in order to propose new criteria in the performances of hair products. The in vitro evaluation of hair swatches movement allows us to better understand the phenomena that appear when various hair care and styling technologies are applied upon the mechanisms of hair movements. METHODS: The method consists of a video acquisition system with fast cameras (100 frames/second). The swatch is placed on a motor drive and moved with a back and forth movement. The frequency and amplitude are set by the operator. Facing each camera, a backlight provides high contrast to capture all the fibres of the swatch. A software was specifically developed to analyse the video recordings and provide the physical parameters that characterize the movement. Accordingly, it is possible to follow the surface and shape of the swatch during movement from the 'skeleton' of the swatch and to study the contraction and expansion phases of the swatch(es) during the movement together with 'the envelope' of the swatch. RESULTS: Results show that applying various hair treatments modifies the behaviour of the swatch through the hair shapes contraction or expansion induced by the oscillating movement. Expansion of the swatch suggests that the interactions between hair fibres (adhesions or frictions) play an important role, leading to an 'individualization' of hair swatch (more 'space' between fibres) or to a 'wider' movement related to the increase of the total surface developed by the swatch. As an example, the application of a highly conditioning formula on a hair swatch largely decreases its expansion by a two-fold factor during movements and increases the horizontal amplitude by a two-fold factor, as compared to a commercial bland shampoo. CONCLUSION: In conclusion, this method is complementary to the ones used generally to characterize global visual perceptions (colour, styling, shine). This dynamic component not only opens doors to new qualitative evaluations, linked with sensorial experts and consumers perceptions, but also to new quantitative parameters.

Resistance of human hair cuticle after a shaking process in wet conditions: comparison between Chinese and Caucasian hair.

Hair cuticle is the first protection shield of hair against external aggressions such as daily combing or brushing that induce friction, mechanical stress leading to ageing process. The identification of alterations of the hair surface induced by shaking process of various hair fibres, such as virgin and chemically treated Chinese and Caucasian hair, sheds some light on some specific features, e.g. Chinese cuticle is torn out in smaller particles than Caucasian, which seems to be related to geometrical rather than ethnic reasons. The present work also shows that two geometrical parameters of human hair, the inter-scale distance and the scale angle are directly linked to fibre dimensions, regardless of ethnic origin. Representative of hair with an average larger cross-sectional area, Chinese hair shows a slightly smaller inter-scale distance as well as a higher scale angle. On the other hand, Chinese hair cuticle seems to be more sensitive to chemical treatment than Caucasian hair, at least for straightening treatment taken here as an example. Such an approach can be of interest in designing cosmetic products more suited to specific needs of human hair.

Chronological ageing of human hair keratin fibres.

Examination of very long hair (length > 2.4 m) using a large range of evaluation methods including physical, chemical, biochemical and microscopic techniques has enabled to attain a detailed understanding of natural ageing of human hair keratin fibres. Scrutinizing hair that has undergone little or no oxidative aggression--because of the absence of action of chemical agents such as bleaching or dyeing--from the root to the tip shows the deterioration process, which gradually takes place from the outside to the inside of the hair shaft: first, a progressive abrasion of the cuticle, whilst the cortex structure remains unaltered, is evidenced along a length of roughly 1 m onwards together with constant shine, hydrophobicity and friction characteristics. Further along the fibre, a significant damage to cuticle scales occurs, which correlates well with ceramides and 18-Methyl Eicosanoic Acid (18-MEA) decline, and progressive decrease in keratin-associated protein content. Most physical descriptors of mechanical and optical properties decay significantly. This detailed description of natural ageing of human hair fibres by a fine analysis of hair components and physical parameters in relationship with cosmetic characteristics provides a time-dependent 'damage scale' of human hair, which may help in designing new targeted hair care formulations.

Adhesion and friction of PDMS networks: molecular weight effects.

The objective of this work is to find relations between adherence and friction behaviors of elastomer networks. The chosen approach is based on the parallel study of the initial molecular weight (i.e., the degree of cross-linking) dependence of both adherence and friction. The polymers used are cross-linked polydimethylsiloxane (PDMS) and the substrate is a smooth glass plate. The experimental procedure uses both friction (pin on disk tribometer) and adhesion (tack test) measurements, associated with surface analysis and mechanical and rheological characterizations. Tack results show that high molecular weight PDMS exhibits the greater adherence energy. This can be explained by the role of both chain length and free and pendant chains: more numerous and longer free chains favor the substrate wetting (at a molecular scale) and increases the energy dissipation during separation (extraction and reptation mechanisms). However, friction results indicate a higher friction resistance for low molecular weight PDMS. This result could be quite surprising. An explanation based on interfacial sliding properties of free and pendant chains can be proposed. Elsewhere, for the lower molecular weight polymer, elastic contact present during friction is able to act as a forced wetting, constraining the network and consequently leading to a greater energy dissipation.