All materials interact with light in some manner, but few record a view-able image. Very few materials record an erasable, viewable image. Thus, the invention by W. H. Armistead and S. D. Stookey (Ref. 1) of photochromic glass offers the possibility of devices using image write-read-erase capability. Photochromic glass is formed by precipi-tation of silver halide crystals of 50 to 100 A diameter spaced 500 to 1000 A apart in a glass matrix as described by G. P. Smith (Ref. 2). The possibility of fabricating large pieces and of using the many glass manipulation pro-esses gives photochromic glass advantages over crystalline materials for practical applications. G. K. Megla (Ref. 3) has described the optical properties and an appropriate system of units to characterize the features of photochromic glass. He has also described experiments demonstrating that photochromic glass is free of fatigue, at least to 300,000 cycles of operation. It may be added that no evidence of fatigue in photochromic glass has been encountered in our work. G. K. Megla and D. R. Steinberg (Ref. 4) have described a time-sharing computer terminal using the image storage CRT incorporating the photochromic fiber optic plate discussed here. This use of photochromic glass places many requirements on the material. Considerable effort has been expended both to configure the system to minimize material requirements and to measure material performance ance relative to system operation.