Adsorption Properties of Hair 358 ninhydrin to reduce the water content of wool30 was demonstrated in the mid 1960s. Similarly, the work of Breuer31 mentions how treatment of hair with phenols is able to produce similar effects. Our own studies have been confirming these findings.32 Figure 19 shows adsorption and desorption isotherms for hair soaked in a 5% resorcinol solution for 60 minutes. Results show around a 20–25% reduction in water content relative to the untreated control. Indeed similar results have been obtained for comparable treatments involving a variety of phenolic molecules. A hypothesis for this occurrence involves these molecules adsorbing within the hair with subsequent blocking of water adsorption sites. Thus, moisture uptake is precluded by steric factors. Our studies have also shown how many carboxylic acids are able to produce similar effects. For example, Figure 20 shows adsorption and desorption isotherms for hair soaked in 10% citric acid for 2 hours at 40oC. While this water retarding ability is intriguing, it is noted that diffusion of these species into hair appears relatively slow, Figure 18. Adsorption isotherm for hair soaked in a 5% glycerol solution relative to an untreated control