The paper correlates the data recorded in Stazione Sperimentale del Vetro. in many years. The aim is to define a correlation between the following parameters in heat treated glass: 1) bending strength tested according EN 1288-3 ; 2) fragmentation tested according relevant Standards [EN 1863-1 2004. EN12150-1 2015. https://chefesquipmenters.shop/product-category/call-bells/