Caucasian hair

Hair straightening compositions based on mixtures of ammonium bisulfite [10192-30-0] and urea [57-13-6] have been introduced and have found some apphcation in the Caucasian hair market. The reformulation of the cystine cross-links in bisulfite-reduced hair is best accompHshed by a rinse, pH 8—10, rather than by the use of oxidizing agents (66). 

At low rhodamine concentrations, the rate of diffusion into the hair shaft was sufficiently slow to monitor. A cross section of Caucasian hair exposed to rhodamine at 1 pg/mL is shown in Figure 16. As exposure time was increased, more rhodamine reached the interior of the hair. At 120 min, even though the surface was much brighter than the interior, substantial fluorescence was observed in the interior when compared with unexposed hair or to the 30-min exposure. At a rhodamine exposure of 10 pg/mL for 2 h the rhodamine had penetrated throughout the hair sample (Figure 16). 

Hair care products have traditionally been formulated for Caucasian hair. In 2003 African-Americans made up 13% of the U.S. population and accounted for 30%... 

With regard to racial variation, nothing has been definitely established. Hawk s data [22] appears to show subtle differences in the relative percentages of various amino acids found in the hydrolysates of Ethiopian hair as compared to Caucasian hair. Wolfram has compiled a more complete set of data from the literature of whole-fiber amino acid analysis of the three races, showing overlap in the amounts of all the amino acids from scalp hair for the three major racial groups [31]. Polypeptide isolation and amino acid sequencing rather than whole-fiber amino acid analysis will provide the best means for determining with certainty if any differences exist in the proteins of hair of different races. 

Evans et al. [25] have confirmed these conclusions of Wickett. In addition, the observation that Japanese hair is easy to perm and that fine Caucasian hair, less than 75 pm in diameter, is more difficult to perm was also confirmed. However, these scientists were unable to identify any common characteristics such as fiber diameter or cystine content that would account for this behavior. The fact that fine hair is more difficult to perm than thick hair may be due to the larger ratio of cuticle to cortex in fine hair and the fact that cortex plays a stronger role in waving than cuticle. This explanation is consistent with the experiments by Wortmann and Kure [2], demonstrating that the cuticle does inhibit the reduction reaction. In addition to pH, other important variables that influence the rate of reduction of keratin fibers by mercaptans are temperature, hair swelling, prior history of the hair, and structure of the mercaptan. 

Columns 9 and 10 of Table 8-13 were obtained by multiplying columns 7 and 8 by 1.273. This normalization is required to bring the mean diameter for Caucasian hair to 70 pm, in accord with our data and others [6,106]. Column 10 represents an estimate of the diameters of 95% of the fibers from the populations of the data by Steggarda and Seibert. It is a good estimate of the variability of the mean fiber diameter of human scalp hair (29 to 125 pm) and is in reasonable agreement with the estimate of 40 to 120 pm by Randebrook [102]. 

Factor of 1.273 used to obtain items 9 and 10. This provides 70pm for mean diameter for Caucasian hair, consistent with our data and Yin et al. [89]. 

This suggests that the calculated circular diameter for Mongolian and Caucasian hair averages approximately 11 and 15%, respectively, from the major and minor axes of noncircular fibers. In most circumstances, the assumption of circularity is an acceptable approximation however, this deviation averages approximately 38% for Ethiopian hair, and, therefore, the assumption of circularity for Ethiopian hair is generally not an acceptable approximation. 

Figure 8-25. Caucasian hair fiber with a noncireular shape. Note the indentation in the fiber. Noncircular shapes are common.

Figure 8-26. Caucasian hair fiber illustrating a twist and flattened areas on the surfaee. Another eommon noncircular shape of Caucasian hair.

Figure 8-29. A Caucasian hair fiber with a large indented area on its surface. Note the irregular shape on the rest of the hair created by this indent.

Figure 8-30. Electron micrographs illustrating a common twist in a curl of a Caucasian hair fiber.

Substantivity was tested on virgin Caucasian hair, and damaged hair obtained by a... 

African Hair Caucasian Hair Asian Hair... 

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