LIGHT RADIATION EFFECTS ON HAIR 669 Figure 2. Two shielded aud four exposed sample hair groups iu suulight expostire box jaw post once and secured firmly with a rubber-faced screw clamp. This arrangement did not show evidence of hair damage at the jaw face. The sunlight exposure box (Fig. 2) was fabricated of wood and Penn- Vernon, single-strength sheet glass with provisions for cross-ventilation according to ASTM standards (15). The glass absorbed all radiation be- low 310 nm and transmitted a minimum of 77% of the solar ultraviolet light and 85% of the total solar radiation. The box was placed at a 40 ø position facing southward. The sunlight exposure was recorded as total incident radiation with measurements supplied by U.S. Weather Bureau Reports (16). The pretested hair samples were mounted in Atlas speci- men holders No. SI.-I.SR* (Fig. 3) and placed in the box at a distance of 3 in. below the glass for the 10-week exposure period. The exposures to ultraviolet light were conducted in an Atlas Fade- Ometer,* Model 18FT, with an enclosed carbon arc. The hair samples were placed in the No. SL-LSR specimen holders at a distance of 10 in. from the arc. The temperature was maintained at 37øC and the relative humidity was controlled at 65% during the exposure period. The car- * Atlas Electric Devices Company, Chicago, Ill.

670 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 3. Samplc hair group mounted in Atlas SL-LSR specimen holdcr bon arc was designed to simulate the effect of sunlight in the visible and UV regions of the spectrum with a radiation output of 155 g-cal/cm2/hr. Procedures Preparation of Hair samples The hair samples were obtained from a private source and certified to be untreated virgin hair. That is, they were free of cold wave treatments, bleaches, and permanent hair colors. A 2.5-in. section of the hair sample was tested from a central portion of an 8-in. strand and precautions were taken to retest the same section of hair on the second elongation test. In addition to exposing untreated virgin hair, groups of bleached hair were also exposed to irradiation sources. The bleach treatments were per-