October 12, 2025
Float Glass: Secondary Glass Manufactoring and Mechanical Properties
In this video Mauro Overend explains how annealed glass is strengthened after its initial production. The primary method is thermal treatment, known as tempering or toughening, where the glass is heated and then rapidly cooled. This process creates internal stresses, putting the outer surfaces in compression and the inner core in tension, which significantly increases the glass's strength. There are two grades: fully-toughened (tempered) glass, which is 3-4 times stronger than annealed glass and breaks into small, less hazardous fragments, and heat-strengthened glass, which is about twice as strong but breaks into larger, sharper shards. The video also covers lamination, a process where two or more glass sheets are bonded with an interlayer (like PVB or SentryGlas®) using heat and pressure. Laminated glass holds together when broken, preventing injuries from falling shards and providing post-fracture resistance, which is essential for safety applications like balustrades and overhead glazing. These secondary processes are crucial for improving the strength and safety of glass in architectural applications. The video was produced by the Open GLASSroom project. Special thanks to Mauro Overend for contributing to the Open GLASSroom OER collection. The creation of these resources has been (partially) funded by the ERASMUS+ grant program of the European Union under grant no. 2022-1-DE01-KA220-HED-000089750. Neither the European Commission nor the project's national funding agency DAAD are responsible for the content or liable for any losses or damage resulting of the use of these resources.