The development of a pre-stressed (¿toughened¿) glass insulator

The first part of the paper briefly describes the manufacture of glass. This description is followed by a discussion of the development of strain in cooling glass, and ¿toughened¿ glass is shown to be glass which has been so cooled as to produce a state of high compression in the surface layers. An account is given of the application of toughened glass to the manufacture of power-line insulators, and the paper concludes with a summary of the tests made during the development period.