OSMOTIC BEHAVIOR OF HAIR DURING PERMANENT WAVING 429 70 • 5WELLINO 6O 5O 4O 3O 2O 10 LOTION NEUTRALIZE 2 4 6 TIME (MINUTES) Figure 2.--Regularcold wave process. 8 10 In the graph (Fig. 2), it can be seen that in the first three minutes of exposure to the cold wave lotion there is a marked and sharp increase in fiber diameter. However, during the second step of rinsing and removal of the cold wave lotion, there is a further increase of diameter which is of paramount significance to this study. The third step of neutralizing reveals that a noticeable deswelling takes place. The following explana- tion is proposed: It is almost axiomatic that in the first three minutes a rapid swelling occurs, due to the rupture of the three bond forces in the fibral structure. However, the additional swelling which takes place upon removal of the cold wave lotion can only be due to some external force influencing the physical state of the fiber, and it is believed that this further increase in swelling is due to osmotic pressure. The cold wave lotion which is applied to the hair penetrates the fiber and initiates a swelling action by absorption (3). The environment surrounding the hair fiber consists of the ammonium salt of thioglycolic acid. After penetration into the hair shaft, the salt content is of equal

430 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS concentration on the outside of the hair as well as the inside. When the cold wave lotion is rinsed off the hair with water, there is an obvious de- crease in salt concentration outside of the hair. However, the salt con- centration remains comparatively higher on the inside of the hair. The- oretically, the hair, acting as a semi-permeable membrane, permits the natural travel of water from the outside of the hair (the less concentrated area) to the inside of the hair (the more concentrated area). In order to • $•ELLING 70 6O 5O 4O 3O 20 LOTION NEUTRALIZE • •'. • NaC• W•sh •10• NaCI Wash 2 4 6 8 10 TIME (MINUTk $) Figure 3.--Difference in swelling rates due to equalizing osmotic pressure during rinsing. prove that this theoretical condition exists, an experiment was performed using various concentrations of salt solutions as the rinsing medium. The purpose in doing this was to see whether the osmosis of fluid into the fiber and subsequent swelling could be avoided. In Fig. 3, it can be seen that the usual amount of swelling takes place within the first three minutes. At this moment, the cold wave lotion is rinsed from the hair for one more minute with deionized water. As can