EVALUATION OF HAIR FIXATIVES 67 Figure 1. Torsional Braid Analyzer cross-sectional diagram of this apparatus (Fig. 2) shows the sample chamber isolated from the outside environment. Any desired atmosphere of gas may be passed through the chamber, entering at the top. A linear-with-angle optical transmission disc (transducer) converts the torsional motion of the sample into a convenient electrical readout. An optical system is used in which a ••_ •.,4..,.TWO WAY SOLENOID ON MANDREL SUPPORTING ROD ,!, EXTENDER ROD COOLING INPUT ............. •-z.J,?l, I I MAGNETIC STABILIZER •) ,ig LIGHT SOURCE Figure 2. Schematic diagram of the Torsional Braid Analyzer

68 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 3. Twist Retention hair swatch Constant light source is attenuated by the transducer and relayed to a linear-response photocell. Voltage readings were recorded on an Omniscribe © 5110-22 recorder. Humid air was introduced into the sample chamber by passing purified compressed air through water, using glass dispersion tubes (Ace Glass a #7202 porosity C) to insure adequate moisture saturation (Fig. 1). Air flow rate was accurately controlled within a working range of 15 to 200 ml/min. Relative humidity of the test environmental air was determined to be 90 to 93 per cent R.H. Temperature was controlled at 21 to 25øC. TWIST RETENTION TESTING Approximately 0.25 g of 25 cm long Remi Blue String, European, brown hair 4 was saturated with water and combed into a swatch free of twists. The swatch was then care- fully bound at both ends with copper ring lugs (size 4) placed 203 mm apart. The hair swatch was allowed to dry at room temperature for 1 hr after which an adhesive was ap- plied at the ring lug/hair junctions to permanently affix the hair to the ring lugs. The watch was conditioned for 16 hr at 50 per cent relative humidity before adjusting (by trimming) to a net hair weight of 0.20 to 0.21 g (Fig. 3). ß :,Houston Instruments, l Houston Square, Austin, Texas 78753. a..Ace Glass Inc., Vineland, New Jersey 08360. •,DeMeo Brothers, New York, New York.