64 JOURNAL OF COSMETIC SCIENCE pounds using another technique. We investigate changes in hair fiber creep as a result of cationic treatments. We are able to show that creep (under special conditions) is significantly inhibited in hair fibers treated with cationic compounds, which corrobo- rates the results of the scale-lifting study. THE ROLE OF CATIONIC CONDITIONING COMPOUNDS ON SCALE LIFTING DURING EXTENSION EXPERIMENTAL MATERIALS Hair fibers. Four 1.2-g skeins of root sections of 14-inch-long, dark brown, unaltered European hair from DeMeo Brothers were prepared for this study. One skein of unaltered hair served as control. Cationic conditioning compounds. The following model cationic compounds (MCCs) were investigated: 1. Polyquaternium 10 (PQ-10) (polymeric) 2. Quaternized hydroxy propyl guar derivative (HPG) (polymeric) 3. A monomeric, low-molecular-weight, cationic quaternary compound, cetyl trimethyl ammonium bromide (CETAB) Aqueous solutions (0.5%) of the three MCCs were prepared by moderate stirring at 35øC. APPLICATION OF MCCs TO HAIR The prepared microskeins were moistened in deionized water (40øC), blotted, treated for two minutes with 2 ml of the 0.5% solutions of the MCCs (well stirred prior to application to provide homogeneity), and rinsed three times for 20 seconds in 200 ml of deionized water at 40øC while actively swirling the microskein and sometimes stroking the fibers in the "with-scale" direction. This was followed by blow-drying at moderate temperature. A total of ten such applications were carried out. An appropriate number of hair fibers was taken after the first and tenth application for scale-lifting studies. METHODOLOGIES Microfluorometry. Unaltered hair fibers, and hair fibers treated once and ten times with the respective MCCs were mounted individually on a small metal frame and gradually extended in steps at -45% RH at room temperature. The ongoing extension of the individual hair fibers was observed in autofluorescence in the UV excitation beam of a Leitz MPV 1.1 microspectrophotometer with a vertical Ploem illuminator. (These ob- servations can also be carried out in the brightfield in complete white light in the incident beam.) The specific extensions at which certain levels (types) of scale lifting occur were recorded. The appearance of the surface cuticle cell as it lifts was classified in four different categories, (A-D). Category (A) denotes the surface cuticle cells of the

CATIONIC CONDITIONING COMPOUNDS 65 unextended hair fiber. The types of scale lifting observed during these extensions are: (B) the start of random scale edge lifting and a brilliant line at the scale edge, (C) scale edge lifting that has become a common occurrence, and (D) extreme scale edge lifting in frequency and angle. Finally, hair fiber breakage occurs. Figure 1 depicts typical ex- amples of hair fibers observed in autofluorescence in the microspectrophotometer prior to extension (a) and at highest levels of extension, showing extreme scale edge lifting (b). The extensions at which the specific levels of scale lifting and fiber failure occur were recorded and are presented in graphs. SEa4. A Hitachi S-4500 digital field emission SEM was used for a detailed topographical study of the longitudinally viewed hair fibers. Untreated hair fibers and fibers treated once and ten times with the respective MCCs (before and after extension to failure) were mounted on SEM stubs on double-sided tape and coated with 100 /• of platinum. Scanning electron microscopy with its higher magnifications of the fiber's topography will reveal whether and how these conditioning compounds affect the stress release mechanisms during extension. Figure 1. Hair fibers observed in autofluorescence in the optical microscope prior to extension (a) and at highest levels of extension, showing extreme scale edge lifting (b).