Significance Of Normalised Retardation Values In Stress Measurement

Cord and annealing stresses in glass containers are assessed typically by polariscopic equipment. The main parameter measured in these analyses is the retardation of polarised light, caused by cord streaks or annealing stresses. Recently, a calculation has been made in the industry of what is termed a "normalised retardation" value. In this article, the author discusses the relevance of its use.