Technology: Through a Glass Darkly

The glass looked as transparent as the standard windowpane, but scientists at the Manhattan meeting of the American Physical Society were impressed by its strange qualities. On brief exposure to sunlight the glass turned grey. Back in the shade, or in ordinary artificial light, it promptly turned clear as window glass again.

Chemist S. Donald Stookey of Corning Glass Works explained that the strange "photochromic" glass, which he had invented along with Dr. William H. Armistead, contains submicroscopic crystals of silver halide, 128 million billion of them per cubic inch. They do not affect its color or transparency, but strong visible...

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