Full-color photosensitive glass

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Abstract
New polychromatic (full‐color photosensitive) glasses are described in which the full color spectrum is developed by photochemical precipitation of subcolloidal silver too small to scatter light. The brilliant colors are shown to be due to selective light absorption by randomly oriented silver‐containing particles having controlled anisotropic shapes. The color photographic process and its chemistry are outlined. Controlled anisotropy is due to photo‐silver‐nucleated growth of elongated NaF⋅ (Na,Ag) X pyramidal crystallites, concentration of AgX at the apex, and subsequent photoprecipitation of this silver. Resultant colors are primarily a function of exposure flux (intensity × time) employing ultraviolet light (300 nm). The colors can be semiquantitatively described from electromagnetic theory assuming ellipsoidal metal particles suspended in a transparent dielectric medium. An absorption band moves across the visible spectrum as a function of particle eccentricity. Polychromatic glasses can be made having transparency, opacity, or a mixed pattern through photonucleation control of halide crystallite growth, which governs light scattering. Colors may be developed in either clear or opal areas; they can be restricted to the surface of the glass or generated to great depth. The colors appear permanent at ambient temperature and exhibit good thermal stability.