TESTING
“Classic” biophysical methods for hair & scalp
C. Uhl, D. Khazaka, A. Pouladi – Courage + Khazaka, Germany
Hair is not only strands of horn made mainly of keratin.1
Hair indicates someone’s personal beliefs
or social status. The matter of hair care / grooming is not all about women. For men, a well-kept, thick head of hair brings added good looks. However, there is more to it. Nowadays, social media, most of all Instagram, influences different generations. Besides skin, hair is the characteristic attribute for health, youth and attraction. Hair can even be a communication and political instrument. Just take as an example the men who grow a moustache of their own style every November, the so called Movember, to raise funds for men´s health.2
Plenty of products and treatments are
ready to fit the modern hair care market for thin, thick, curly, dry, oily, blonde, coloured, ethnic, young, or old hair. Imagine a claim, the product is already invented. As hair is unique, personalised products flood the hair care market. Respectively, a great number of claims around the various products exists. Hair care rituals can be complemented with food supplements and treatment devices.3
Tests on hair tresses In this context, claim-related best practice in vitro biophysical methods, including instrumental methods (mechanical and visual) to hair fibre characteristics have been established.4,5.6 The most widely used instrumental-based
mechanical test to measure the efficacy of shampoos, conditioners, masks and other hair care products is the combing forces test on hair tresses as it supports a broad range of claims. Wet and dry combing forces are determined to substantiate claims such as combability, conditioning, detangling or easy-to-comb. Mechanical measurements of hair breakage provoked by multiple combing of hair tresses show how effective hair care products are regarding protection or resistance to hair damage caused by
10 2.5% 0 5 min or less 6 to 15 mins 16 to 30 mins 30 mins to 1 hour 1 hour or more 8.5% 5.5% 50 43.5% 40 35% 30 23% 20 14.5% 11% 29.5% 29.5% Female■ Male ■
23
Figure 1: Estimated daily time spent on personal appearance and grooming worldwide as of 2016, by gender. According to the survey, a 14.5 percent share of females spent on average an hour or more per day on their appearance. (
https://www.statista.com/statistics/805935/daily-time- spent-on-personal-appearance-and-grooming-by-gender-worldwide/)
combing. The amount of broken hair fragments is determined to support claims such as anti-split ends or anti-breakage. Friction tests, where a bar is pulled along a hair
tress, are applied to support claims like smooth and silky performance. The tensile properties of hair depend on its
inner structure. Their measurement offers a view into activities lying within. Hair strength is affected by a wide range of influencing factors, so it is often seen as a primary measure of hair damage which can be analysed with the Single Fiber Tensile or Single Fiber Fatigue Test. Differential Scanning Calorimetry (DSC) is performed for supporting claims such as heat-
and UV protection through denaturing of keratin upon heating. By applying this method, the thermal resistance of hair’s major morphological components is determined. Hair consists of 12 to 15% of water, which is one
of the most important fibre properties. The water content of hair can be measured through the Hair´s Technical Water Content Test. The main factor to determine hair water content is the relative humidity of the surrounding atmosphere, and this relationship is given via the hair water adsorption isotherm. Bending tests support claims like long lasting
hold and strength of fixation. There are three different test types depending on the product to be evaluated; such as bending the hold-providing film, remaining hold and flexibility of the hold. For assessing hair shine/gloss, colour, curl
retention and volume, visual tests have become standard in practice. Hair gloss assessment for example is mostly performed visually by an expert panel; colour protection and anti-colour fade products or the durability of colour-dyed hair are measured by using a Colorimeter and the volume of a hair tress can be assessed using a silhouette technique followed by image analysis.
Figure 2: Reaching the hairy scalp with the Sebumeter® foil and a special adapter.
www.personalcaremagazine.com
Testing hair and scalp in vivo For the hairless skin, objective testing methods
March 2021 PERSONAL CARE
Share of respondents (%)
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