Glass polarizer for visible light

A method of producing a glass polarizer that is effective to polarize light radiation across the entire visible wavelength region of the spectrum which comprises the steps of melting a batch for a R.sub.2 O--Al.sub.2 O.sub.3 --B.sub.2 O.sub.3 --SiO.sub.2 base glass containing at least 0.2% by weight Cu.sub.2 O together with a sufficient amount of at least one halogen selected from the group consisting of chlorine and bromine to react with at least 0.2% copper, precipitating a cuprous halide crystal phase in the glass in an amount that constitutes over 0.003 volume fraction of the glass, subjecting the glass to a stress in one direction of at least 17.25 Mpa (2500 psi) to elongate the glass and the cuprous halide crystals therein, and then exposing the glass to a reducing atmosphere to reduce at least a portion of the copper halide crystals in a thin layer near the surface of the glass to impart permanent dichroic behavior and polarizing capability across the entire 400-700 nm wavelength range the efficiency of the polarizing capability, calculated on the basis of a standard defined by the formula, ##EQU5## wherein T max is the transmittance of the perpendicular component of polarized light T min is the transmittance of the parallel component and employing transmittance measurements at a wavelength of 500 nm, being at least 0.80.