Synopsis

Heat-styling of hair is an established and popular consumer habit, exploiting the well-known thermally-induced glass transition in hair fibres to plasticise, re-shape then re-set the hair. Whilst the hair fibre glass transition itself is reversible, the application of heat to hair fibres can also cause irreversible configurational and chemical changes, ultimately leading to degradation of the structure of the hair fibre. Colloquially, this is referred to as heat damage, which is now the focus of significant consumer awareness and concern. In this presentation we discuss the selection of a preferred method for quantifying thermal damage to human hair based on considerations of sensitivity, robustness and physical relevance. We also discuss the utility of these measurements to the consumer with particular emphasis on the need to provide sound scientific guidance to those seeking to achieve fantastic styling results without suffering from perceivable detrimental effects of thermal damage to their hair.