594 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 14. Recording goniophotometer assembly. In front, reading from left to right, are recorder, switch box, amplifier, and GP-2 in rear are lamp power supply, the Wave Tek Generator, HP Counter, and large box which houses power supplies for magnetic clutch and stepping motor and also translator module. Step- ping motor and exhaust fan are behind GP-2. Black box on top of GP-2 is large light trap or "black hole" which traps light transmitted by sample and also excludes room light from cavity of GP filters* with a wide variety of transmission values (T equals 0.01 to 0.5) to supplement those provided by Zeiss (T equals 0.001, 0.01, and 0.1) so that the strongest signals can generally be made to provide a full-scale deflection on the chart paper to provide a sta- ble light-detecting device possessing adequate sensitivity (UDT? PIN-3008 (Special PIN-10DF) Diffused Si Photodiode with flat (-+7 per cent) response 400 to 700 nm), an amplifier (UDT? 10lB) with a low-noise level and a 2-pen recorder (Houston Omniscribe Recorders Model 5213-15) provided with an integrating circuit so that a number (called counts) proportional to the area between the curve and the baseline can be obtained directly from the integrator trace on the chart paper without having to use a planimeter to provide a light-tight air inlet, an air outlet, and an exhaust fan for the cavity of the GP-2 in order to maintain constant temperature and RH inside the cavity for the sake of the hair samples and to prevent overheating of the Si photodiode detec- tor which is temperature sensitive. *Neutral density glass filters from Fish-Shurman Corp., 70 Portman Rd., New Rochelle, NY 10801. Perforated metal screens from Perforated Products, Inc., 68 Harvard St., Brookline, MA 02146. '•United Detector Technology, Inc., 2644 30th St., Santa Monica, CA, via Scientific Devices, Inc., 60 Con- nolly Pkwy., Bldg. 11, Hamden, CT 06514. ++Houston Instrument, One Houston Square, Austin, TX 78753, via Scientific Devices, Inc., 60 Connolly Pkwy., Bldg. 11, Hamden, CT 06514.

OPTICAL PROPERTIES OF HAIR 595 The elements employed in the mechanization of the scanning arm (LH side of Fig. 6) are shown in Fig. 13, and are listed in the caption of that figure. In mechanizing an exisiting piece of equipment, difficulties are generally encountered in coordinating the numbers on the existing instrument (in this case degree marks on the scale of the Zeiss GP-2) with the time-scale lines on the chart paper of an existing recorder. The recorder selected (Houston Series 5000) has a variety of fixed paper speeds (1, 2, 4, or 10 in./min, + 1, 10, or 60). One revolution of the hand wheel on the GP-2 alters the scale reading by 23.3 ø so it appeared sensible to drive the gear train with a stepping motor (DC square-wave pulses) in order to be able to fine tune the speed of the GP-2 in a re- producible manner and achieve essentially perfect coordination of the degree marks with the time scale on the chart paper. It was decided to allow 15 mins for scanning the interval 0 to 75 ø at 5ø/min which translates into a chart speed of 1 in./min with 1ø/0.2 in. of chart paper and 286.2 pulses/sec to the stepping motor whose shaft rotates at 1.8ø/pulse. Silver-tipped set screws were employed for all couplings to avoid scoring the shafts. Because the motor has high torque and also because its speed has been stepped down -. Figure 15. Interior of GP-2. Illuminating system is to right in 30 ø position telescope which is mechanized and carries detector is in center at 0 ø position. Nonblackened brass parts at end of each tube hold rotatable Polaroid discs. On top plate can be seen long slot over which sample is placed when in use, fibers are in plane defined by this slotted SS plate. Rack on which fibers are strung is upside down and to rear of slot. Filter holders are shown at each end of slot