Annealed Glass This is the most common type of glass used today. Produced using the Float method, molten glass is poured continuously onto a bed of molten tin. Because the melting point of tin is less than glass, the glass solidifies as it cools on top of the tin. Increasing or decreasing the rate of molten glass flow onto the tin can control thickness levels. Once the glass becomes solid, it is then cooled in an annealing oven to remove any residual stress. Annealed glass is the most fragile type of manufactured glass because of the relatively low amount of surface heat compression. When glass breakage occurs, it does so in many small and irregularly shaped pieces.
Heat-Treated Glass Heat-Treated Glass is twice as strong as annealed glass. This process takes annealed glass and heats it to its softening point (1200 degrees F) where it is controlled and cooled using water. Water cools the surface of the glass quicker than the interior glass, thus providing an extra degree of surface compression. An increase in the rate of cooling will result in a stronger surface compression. Heat Treated glass is stronger than standard annealed glass, and is more resistant to stress caused by heat, wind and flying objects (but not as strong as safety glazing products).
Types of Glass Construction
Basically, there are 3 types of glass construction:
1. Monolithic Glass Monolithic glass is the most basic of glass forms. It is simply a single piece of glass constructed using one glass thickness. Monolithic glass is produced using either the annealed, heat-treated or tempered glass float method.
2. Laminated Glass Laminated glass is constructed by combining two panes of glass fused together with a middle layer of Polyvinyl Butylenes Film (PVB). PVB acts like a bonding agent to hold broken glass together. This feature creates an effective barrier against entry and reduces the chances of flying shards of glass. Automotive windshields and buildings/homes in hurricane areas (e.g. Florida) use laminated glass.
Diagram A: Shows the basic Monolithic Glass.
Diagram B: Shows Laminated Glass with the Interlayer of Polyvinyl in the middle.
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