HAIR-HAIRSPRAY JUNCTIONS 173 Figure 4. A. Shattered knot from hair spray C 1. B. Piece of shattered resin from C 1 showing cuticle scale pattem. N robust ranged from 15 to 19. Means varied from 17.5 to 23.5 grams and standard deviations from ---3.3 to ---9.2. The 95% confidence interval is calculated by multi- plying the standard error of the mean by the percentile of the Student's t distribution based on N-1 degrees of freedom.

174 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table I Reproducibility of Knot Adhesion Data Using a Commercial Hairspray (C1) Standard 95% Confidence Test N robust Robust mean deviation interval T1 15 18.0 +3.3 +1.8 T2 17 17.8 +5.6 +2.9 T3 15 23.7 +8.1 +4.5 T4 19 17.5 -+9.2 +4.4 COMPARISON OF COMMERCIAL HAIRSPRAYS Knot adhesion testing was performed on 11 commercial aerosol hairsprays. These in- cluded a product available only in beauty salons and labeled as ultra-high holding (HH Salon), five mass-marketed products labeled as extra, super, or for haM-to-hold hair (HH A-E), four products labeled as regular- or normal-hold (RH A-D), and a light-hold product (LH A). Results are given in Table II. N-robust varied from 20 for several of the products to 15 for LH A. Mean breaking strengths varied from 37.8 for the salon product to 10.0 for the light-hold product. The mean adhesive strength of the light- hold product was significantly lower than for any other product tested in this series. Products marketed as higher-holding generally formed stronger knots than the regular- hold variants, with the exception of HH E, which is marketed as "Super Hold" but only gave an average knot strength of 20 grams. We observed this product to have a very forceful spray. Perhaps higher-hold levels are delivered to the consumer by delivering more spray to the hair. EFFECT OF DILUTION Results of diluting a hairspray formulation with absolute ethanol are shown in Table III. C2 is a mass-marketed hairspray based on vinyl acetate/crotonic acid copolymer. Dilu- tion produced relatively little effect on the mean force to break robust knots but did Table II Knot Breaking Testing of Commercial Products Standard Product N robust Robust mean deviation HH Salon 20 37.8 -+ 11.9 HH A 19 30.6 -+ 11.7 HH B 20 29.5 +11.4 HH C 19 28.1 -+9.9 HH D 20 26.7 -+ 10.2 HH E 18 20.0 -+9.3 RH A 19 25.4 -+7.2 RH B 20 24.5 -+9.6 RH C 20 21.0 -+5.1 RH D 20 19.9 -+7.7 LH A 15 10.0 -+6.2 The minimum significant difference at 95% confidence = 8.0 by Duncan's multiple-range test.