MEASUREMENTS ON 1IUMAN HAIR 385 the wide-tooth section of a hand comb and finish using the thin-tooth section. Step 4: immerse the hair swatch 3 consecutive times in a separate beaker con- taining aleionized water at room temperature. The purpose of this step is to generate a certain degree of tangling of the swatch under controlled condi- tions. This step is very important and care should be taken to perform it in the same way each time. It should be done by holding the swatch through the damp and gently dipping it in and out of the water 3 times. After the third immersion, squeeze out the excess water twice with the fingers. Step 5: with the crossbar suffieienfiy out of the way (below), hang the hair swatch from the load cell hook and adjust the pen of the recorder so that the swatch plus the damp read zero. To do this, use the balance control of the recorder, which does not affect its calibration. Step 6: remove the swatch from the load cell and hang it by its damp dose to the Instron. Displace the crossbar upward to the starting position. At this point, the teeth of the comb should be at a dis- tanee of 2.5 em from the lower edge of the hair swatch damp. Step 7: hang the hair swatch from the load cell, and using two fingers to fiatten the swatch, push-guide the hair into the comb. If done carefully, this operation insures a fairly even distribution of the hair between the interteeth spaces. Also, be- cause the width of the swatch at the damp is 2.8 era, and the distance between the 2 outer teeth of the comb is 3 era, it is simple to have all the hair "in" the comb. Place the thin metal rod below the teeth, perpendicular to them, to pre- vent the hair from coming out of the comb during the measurements. Step 8: once the hair is properly placed in the comb, the actual measurement can be started. This consists of continuously recording the force that is required to move the comb down through the hair swatch at a constant speed. This is done by setting the crossbar in downward motion while continuously record- ing the load. If a recorder integrator is available, it should be functioning so that the area under the combing curve is measured. The combing speed will be set at 10 em/min and the chart speed at 10 em/min. The sensitivity for the recorder will be set according to the values of the forces encountered. Step 9: repeat steps 4 through 8 twice for the same swatch in order to record tripli- cate runs. Step 10: repeat steps 2 through 9 for the remaining swatches. Step 11: after the wet measurements are eompleted, comb the swatches using the hand comb, hang them through the damps and allow them to dry and condi- tion for at least 24 hours at 65 per cent RH and 70 ø F. Dry Measurements: Dry measurements comprise steps 12 and 13. Step 12: Start the dry measurements by taking the first conditioned hair swatch and combing it with the hand comb until no derangling is noticed on further combing. Proceed then with steps 5 through 9 as before. Step 13: repeat step 12 for the remaining swatches. Treatment: Give the treatment to the hair mounted on the clamps fol]owing the recommended instructions for the product. Use deionized water whenever

386 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS water is needed. The amount of product to be applied to each hair swatch is calculated taking into account the amount recommended for a head of hair, using 100 g of hair as the average weight of hair for adult females, and weight of hair in each hair swatch. The following formula is applied for this purpose. Weight of product (weight of hair swatch) x to apply per swatch = 100 Amount of produc recommended for a! head of hair If rinsing with water is the last step of the treatment, care should be given to this operation. Rinsing should be sufficient to eliminate excess product, but not so intense so that the effect of a product could be completely eliminated. The way in which the product is used in actual practice should be followed. For example, shampoos are rinsed until foam is no longer evident the same should then be accomplished with the rinsing given to the hair swatches. Once the conditions are specified, care should be exercised in rinsing each of the swatches in the same way. Rinsing conditions should specify volume of water, temperature of the water, finsing time, and method (flowing water or immer- sion). Measurements of Treated Hair: Wet measurements on treated hair should be done right after the treatment, preceded only by a 5-rain period in which the treated swatch is allowed to relax immersed in water. The rest of the wet treated swatches should be left hanging from their clamps while they wait for the 5-min relaxation period and subsequent measurement. The main reason for doing the wet measurements fight after the treatment is be- cause, in practice, the hair has to be combed after any treatment, and it is at that point that the user will associate the product with its effect on wet comb- ability. Obviously, wet measurements can be done at a later time if this will contribute additional information on the effect of the product. Calculations Once the measurements are completed the data required to calculate chang- es in combability are obtained from the combing curves. The PCL for each run corresponds to the highest load recorded for that run and is read directly from the corresponding combing curve. The load for a full-scale deflection use for recording obviously has to be taken into account. The ACL for each run is calculated by first measuring the area under the corresponding combing curve (in grams cm ß units) and then dividing the value for the area by the distance in centimeters that the comb travels through the hair in that run. This distance is read directly from the curve. It has been our experience, in developing this method, that per cent changes in PCL are similar in value to per cent changes in ACL. For this reason, and