Correlating Porosity and Tensile Strength of Chemically Modified Hair

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Here's a study me and my colleague authored in November 2002 exploring the relationship between porosity and tensile strength of hair fibers.

Over the years, many individual studies have been conducted regarding the extent of damage imparted to hair. These studies deal with the damaging effects of various chemical processes such as permanent waves, permanent colors and hair bleaches.

The most commonly employed method to quantify this damage is the measurement of change in tensile properties of the hair. This method takes two to three days in the preparation of samples of hair fibers. It also requires a minimum of 30 to 40 fibers for statistical analysis. Therefore, there is a need for other simpler methods that are equally valid and less time-consuming.

One such method could be the determination of hair porosity or water uptake of hair fibers as described by Valko et al and by Menkart et al. However, to the best of our knowledge, no study so far has correlated the tensile strength method with the water uptake (swelling/porosity) method following chemical treatments such as permanent
waves, permanent colors, hair bleach, and permanent hair relaxers.

Therefore, we have conducted a study whose purpose was to validate the porosity method against the tensile strength method. Another purpose of this study was to use these two methods to compare the magnitude of hair damage between permanent waving, permanent coloring, hair bleaching, and permanent straightening processes. Finally, this study ranked the various chemical processes in terms of their hair damage potential. We believe this is the first comparative damage ranking for various chemical processes in the hair care field.

Swelling or Porosity of Hair

Professionals who are involved in the art of styling hair define the porosity of hair as the capacity of hair%2

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