Abstract: A photochromic material adapted for coating light transmissive materials. The photochromic material contains photosensitive silver halide crystals having dimensions in the range of approximately 50 Angstroms to 800 Angstroms. The silver halide crystals are surface doped with copper ions and another sensitizer selected from mild reducing agents, thioethers, or sulfur-bearing ions and are treated with an agent to accelerate the forward reaction and control the reverse reaction. The accelerants are ions selected from the group consisting of cobalt, chromium, manganese, magnesium, and rare earth metals such as cerium, samarium and europium. The agent for controlling the reverse reaction is one that confers electrical conductivity on the material and while to this end glycerol containing a high concentration of metal ions, methane sulfonic acid and benzyltrimethyl ammonium chloride are useful, the preferred agent is phosphoric acid.