QUANTITATIVE CHABACTEBIZATION OF COMBING FOBCE Table III Comparison of Effect of Conditioner on Wet and Dry Combing Force 779 Dry Force (g) Wet Force (g) Before treatment 12.5 + 2 After treatment a 10 ___ 2 Residual combing force, % 80 Tress weight, g 4.75 •Tress treated with 0.2 ml of conditioner D. 51_4 23_3 45 2.75 100 • 60 z o • 40 co •0 i i/io i/ioo i/i,ooo i/io,ooo i/ioo,ooo r•.6•//• DILUTION Figure 5. Relationship of residual combing force to amount of conditioner Table IV compares the effects of several resins used in experimental men's hair grooms. These materials, intended to "texturize" hair by thickening it and adding "body," increased the combing force. In the cases illustrated, dry combing force was determined. The resins were tested both as applied from aqueous solution and from specific hair groom formulations. Table V summarizes combing force measurements done on bleached hair. The wet combing force was determined for two tresses, which were then bleached once or twice for 30 rain by immersion at room temperature in a so- lution prepared by dissolving 24 g of a mixture consisting of 62% potassium persulfate, 21% ammonium persulfate, 14% sodium silicate (the remainder be- ing flowing, chelating, and wetting agents) in 50 ml of 6% hydrogen peroxide

78O JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table IV Effect of Resins on Dry Combing Force a Resin Type 3% Aqueous Solution Prototype Formulation __ Combing Force Residual Combing Force Residual (g) Combing Force (%) (g) Combing Force (%) Cationic 31 200 21 150 Carboxylated 34 240 35 250 Vinyl 24 170 27 190 SAverage control force = 14 g. Table V Effect of Bleaching on Combing Force Experiment Initial No. of After After No. Force Bleach Treatments Bleaching Conditioning i 80 4- 12 i 225 q- 30 50 4- 10 9. 75+__ 5 2 320 q- 50 75 4-•5 the pH of the solution was 9.4. Tensile strength measurements of the bleached hair were made on a model TM-M Instron* by determining the Fa,5 of indi- vidual hairs before and after bleaching (7). The tensile strength of the hair bleached 30 min was reduced to approximately 85% of its initial value, while that of the hair bleached for 1 hour was 70%. As summarized in Table V, the bleaching caused a large increase in the wet combing force of the hairs. When the tresses were treated with 0.2 ml of conditioner D, a large decrease in the combing force resulted. Although both of these effects have long been known to formulators and consumers alike, the above data represent a quantitative determination of their extent. DISCUSSION The interaction of water with hair and wool and the effects of this interac- tion on the properties of the fibers have been studied and documented for many years ( 8, 9). Two of these interactions that must be considered in trying to understand the much larger amount of force needed to pass a wet tress of hair through the teeth of a comb are discussed below: _ a) The saturation of hair with water will increase its diameter by approxi- mately 14% above that found at an ambient relative humidity of 30 to 40% (9, 10). Therefore, wet hair would occupy that much more volume and be expected to offer more resistance to the passage of the comb. The quantitative effect of swelling on the combing force could be deter- *Instron Corp., Canton, Mass.