Photochromic Glass by Silver Ion Exchange

Photochrome glass that was prepared by silver ion exchange had properties similar to those obtained in glasses containing silver introduced as a batch material. The ion exchange was conducted over the temperature range 250-1150 degrees c with molten salt baths containing from 1 to 100 ion percent silver. Observations made with an optical microscope clearly indicate the photochrome nature of the exchanged layer and permit a measurement of the depth of this layer. The principle advantage of this method over batch melting techniques is the greater intensity of color that can be obtained per unit volume of active sample.