National Geographic : 1943 Jan
The National Geographic Magazine These Girls Demonstrate that Glass Is the "Perfect Elastic" To the layman rubber is elastic because you can pull and squeeze it. But rubber will lose its shape and "give." Glass never does, this side of breaking. Stretch a piece of glass, or compress it for a thousand years, and it will bound back to its original shape. That is what the physicist means by "elasticity" of glass-no flow nor deformation. The girl at left is pulling tempered plate glass out of plane as registered by the ruler. Such glass faces bumps and weathering in doors, portholes, and searchlights. Libbey-Owens-Ford Glass Co., Toledo, Ohio.