Standard Strain Discs - Assessment Of Annealing Quality Of Glassware

Glass articles normally have to be cooled in a controlled manner after forming, in order to prevent the build-up of dangerously high levels of internal strain. The maximum permissible strain in the finished article will depend on various technical and commercial factors and, except for specialised products such as optical glass, "perfect" annealing is normally neither economic nor necessary. Most commercial glassware, after annealing, does contain some degree of internal strain. It is, necessary, however, to ensure that such residual strain is at a level low enough to ensure that it does not give rise to problems in service. This article describes the use of Standard Strain Discs in this context.