68 JOURNAL OF COSMETIC SCIENCE perform differently during hair fiber extension than those capable of either diffusing into the hair fiber interior or achieving both surface deposition and penetration into the cuticular sheath. Our SEM studies had shown significant adsorption of the polymeric cellulose and guar derivatives onto the hair fiber surface, especially at the scale edges, with little or no additional uptake after multiple applications of these two polymers. This appears to indicate saturation of available anionic sites on the hair fiber surface after the first application. Micrographs of typical sorption of the celldose and guar derivatives onto the hair fiber surface are shown in Figures 3a,b and 4a,b, respectively, displaying preferential deposition at the scale edges. The low-molecular-weight CETAB, on the other hand, appears to behave differently from the polymeric materials. After a single application of this compound, the hair fiber surface appears rather "clean" and free of deposits (Figure 5a,b). After multiple appli- cations of CETAB, the surface of many hair fibers still appears rather "clean" (Figure 5c), while other fibers clearly show thin film-like deposits on the scale faces and edges and leave no doubt about the nature of the deposits (Figure 5d). MICROFLUOROMETRIC STUDY OF THE EFFECTS OF MCCs ON SCALE LIFTING To determine the effects of single and multiple applications of cationics on the scale- lifting phenomenon of the surface cuticle cell, hair fibers have been extended up to failure while being observed in autofluorescence in the fluorescence microspectropho- tometer. The extensions at which specific levels of scale lifting and fiber failure occur were recorded and plotted. It should be pointed out that the break extensions observed in this work are different from those observed in a regular tensile test, which is carried out at a higher extension rate (-50%/min.). Break extensions are higher in this case, because of extension of the hair in steps, which allows the fiber to relax between steps. Unaltered hair without MCC treatment. Surface cuticle cells of untreated, unaltered hair fibers tend to respond with various levels of scale lifting to release the stresses of extension, until finally hair failure occurs (Figure 6). Even though there are fiber-to-fiber Figure 3. (a,b) Adsorption of the PQ-10 compound onto the hair fiber surface after a single application of the product, especially at the scale edges.

CATIONIC CONDITIONING COMPOUNDS 69 • •-.•--'• . b 6 ß •.- Figure 4. (a,b) Adsorption of the HPG compound onto the hmr fiber surface after a single application of the product, especially at the scale edges. ... Figure 5. Hair fiber surface after single (a,b) and multiple (c,d) applications of CETAB. variations within each specific level of scale lifting, there is always an increase in the level of scale lifting with increasing extension. This behavior of the untreated hair fiber will be used as a baseline reference for comparison with hair treated with cationic compounds. Hair fibers treated with a PQ-10 derivative. Unaltered hair fibers treated with one appli- cation of cellulose derivative display a scale-lifting behavior rather similar to that ob- served for the unaltered (Figure 6) hair fibers (Figure 7a). Only a few hair fibers did not show the extreme level of scale lifting. There is considerable fiber-to-fiber variation,