238 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table VII Weight, Diameter, and Hairfiber Uncoiling Dia# Wt.# r 2 F(calc) Elastic Deflection -0.66 +0.77 0.89 66.4* Total Creep -- -- 0.03 0.3 % Curl Retention + 0.73 -- 0.29 0.60 11.9' Primary Creep Recovery - 0.34 + 0.78 0.74 22.2* *Significant beyond the o• = 0.01 level (F(req.) = 8.02). #Standardized Coefficients (11) are made standard with respect to the standard deviations of the variables involved. They have greater meaning for relative magnitude comparisons than actual coefficients. combined. Standardized coefficients (11) show that added load increases the deflection, while increasing diameter decreases deflection with the weights used, load plays a slightly greater role than diameter. At 21.5 hours there is no meaningful relationship between total creep and the combined parameters of fiber diameter and added load, under the conditions of this experiment. However, the variation in curl retention to 21.5 hours, which combines initial curl, elastic deflection, and total creep, is explained to the extent of 60 percent by these two parameters. As expected, increasing fiber diameter increases curl retention, while increasing load decreases it. Under these experimental conditions fiber diameter has more of an effect than added weight on curl retention. Since these experiments are with single fibers, fiber diameter is an indirect assessment of fiber stiffness and torsional resistance which are inherently related. So under these conditions, fiber stiffness and rigidity are more important to curl retention than added weight. Since decreasing fiber curl will provide less hair body, these results confirm the conclusions by Robbins and Scott (12) that increasing fiber stiffness increases hair body, and adding weight to hair decreases both hair body and curl retention. For primary creep recovery, 74 percent of the variation in this property is explained by variation in fiber diameter and added load, the latter contributing more than twice as much as diameter to this property. The final, but not least interesting observation, is that after several hours of very minute creep recovery, the fibers, generally after 40 hours, began to elongate once again or to enter a second stage of creep with no added load, but under their own weight and the influence of gravity, i.e., the extensional forces due to gravity at this point in time, exceed the recovery forces from removal of the load, so the coil once again elongates. REFERENCES (1) C. R. Robbins, Chemical and Physical Behavior of Human Hair (Van Nostrand Reinhold Co., New York, 1979), pp 153-183, and references therein. (2) P. Alexander, R. F. Hudson, and C. Earland, lVool, Its Chemistry and Physics (Chapman and Hall Ltd., London, 1963), pp 55-128, and references therein. (3) P.J. Huck and C. B. Baddiel, The mechanical properties of virgin and treated human hair fibers: A study by means of the oscillating beam method,J. Soc. Cosmet. Chem., 22,401-410 (1971). (4) M. M. Breuer, The binding of small molecules to hair. I. The hydration of hair and the effect of water on the mechanical properties of hair,J. Soc. Cosmet. Chem., 23,447-470 (1972). (5) D. E. Deem and M. M. Rieger, Mechanical hysteresis of chemically modified hair, J. Soc. Cosmet. Chem., 19, 395-410 (1968).

LOAD-ELONGATION OF HAIR COILS 239 (6) L. Rebenfeld, H. D. Weigmann, and C. Dansizer, Temperature dependence of the mechanical properties of human hair in relation to structure,J. Soc. Cosmet. Chem., 17, 525-538 (1966). (7) Robbins, pp 173-174. (8) P. Alexander, et aL, pp 55-57. (9) H. Bogaty, Torsional properties of hair in relation to permanent waving and setting, J. Soc. Cosmet. Chem., 18, 575-589 (1967). (10) Design and Application of Helical and Spiral Spring, ASE J795a, Soc. of Automotive Engineers, Inc. (1973). (11) C. H. Goulden, Methods of StatisticalAnalysis (John Wiley and Sons, Inc., New York, 1952), p 144. (12) C. R. Robbins and G. V. Scott, Prediction of hair assembly characteristics from single fiber properties, J. Soc. Cosmet. Chem., 29, 783-792 (1978).