Conditions under which light-pipes with highly reproducible transmittance are prepared are described. Preparation of borosilicate glass tubing by washing with HF and SiCl2 solutions gave the best results. Electron microscopy showed that drawn capillary tubing had a much smoother bore than “precision-bore” (drilled) tubing, and light-pipes constructed from drawn tubing had a much higher transmittance. Annealing the tubes at 800°C appeared to cause the gold coating to be more tightly held to the glass tubing. Light-pipes which had been annealed at 800°C could have small holes drilled through the tube without the gold coating lifting.
