Last Updated: Aug 23, 2018     Views: 8355

Hello! Thank you for your question! Here are definitions of tempered and laminated glass from the Schott Guide to Glass (2nd ed., 1996):

Tempered glass

"..pre-cut pieces of flat glass are vertically suspended above or placed horizontally into processing equipment where they are quickly heated to about 150C above the transformation temperature. Immediately upon exiting from the furnace, the glass is chilled with cold air from an appropriately designed system of air jets. As a result of this fast cooling, the glass surface is 'frozen' in an expanded grid structure whereas the glass inside cools off more slowly, allowing much more shrinkage in the structure. Since they are bound together, the outer surface layer is subjected to compression and the inside to tension.... When tempered glass is damaged ... the glass breaks into many small, almost regularly shaped pieces with no long sharp cutting edges.... In office buildings tempered flat glass is used in glass doors, room dividers, elevator glazing, or stairway landings."

Laminated glass 

"Laminated (or compound) safety glass consists of two or more panes (usually float glass) which are joined with a viscous plastic layer. The solid joining of the glasses occurs in a pressurized vessel called an autoclave where under simultaneous heating of the pre-processed 'sandwich' the lamination takes place.... When laminated safety glass breaks, the broken pieces of glass stick to the internal tear-resistant plastic layer. The pieces do not break away and the broken sheet remains transparent.... Laminated safety glass is used in building windows, where break-in or escape hampering or explosion protection glass is required... It is also used [in] spandrels, in walls, room dividers, and roofs."

Additionally, the Schott Guide to Glass notes that "the risk of injury becomes smaller when the inside sheet of a laminated glass is thinner (1.5mm for example). The same purpose can be accomplished by using a tempered glass on the inside."

So in some cases, these types of glass are combined.

Additional Resources

You might also be interested in the following articles from All About Glass on The Corning Museum of Glass website:

"The Precise Moment: Tempered Glass" (Oct. 25, 2011)

"Prince Rupert's Drop and Glass Stress" (Dec. 1. 2011)

"From a Broken Flask: Laminated Safety Glass" (Oct. 25, 2011)

Online Videos

See the video on "Practical Applications of Tension in Glass" from The Corning Museum of Glass YouTube channel, along with a video on the "Prince Rupert's Drop."

 

A more extensive list of resources is available upon request. Please let us know if we can be of further assistance via Ask a Glass Question (http://libanswers.cmog.org/) or by email (rakow@cmog.org) or phone (607-438-5300).

 

Please do not hesitate to contact us in the future with your glass-related questions!

 

 

 

 

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