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Volume 7    Issue 3            May/June 2005

Off the Line
the oem glass perspective

More Function for Glass
by Russ Corsi

It’s amazing to look back over the years and review the many innovative developments that continue to add more functionality to auto glass.

The very first application of glass on an automobile was a small piece of annealed glass (not laminated or tempered). The introduction of a laminated windshield (two pieces of annealed glass sandwiched together using cellulose acetate as the innerlayer) occurred in 1927. Eventually, laminated glass was added at all glass locations on the automobile.

Tempered glass was developed in 1938 and began playing an ever increasing role for sidelites and backlites. Tempered glass had the flexibility to be formed to much more complex shapes with an overall thickness that was significantly less than laminated glass.

Passenger comfort became an issue as vehicle owners starting driving more miles. Green tinted glass became quite common in the early 1950s. The tinted glass absorbed more of the sun’s heat and became more effective with the addition of air conditioning.

Float glass manufacturing technology allowed glass manufacturers to modify the glass melting batch to include materials that added more heat absorption capabilities for glass and the ability to modify the colors available. Various shades of bronze, blue and gray were added to an ever increasing number of green products.

Metallic coatings were added to the glass that significantly reduced the amount of heat entering the vehicle by reflecting (not absorbing) the heat away from the vehicle. These same coatings could also be used to defrost the glass and to serve as the radio antenna.

Although the emphasis continues on passenger safety, automobile manufacturers have also added a new requirement to the glass functionality bucket—value-added products. 

On-glass antennas have evolved from a wire sewed in the inner layer in the windshield in the 1970s, to the metallic coated application, to a ceramic frit alternative that is silk-screened onto the glass. Multiple antennae have been added on the same piece of glass.

Although initially required to protect the installation adhesive (polyurethane) from harmful ultraviolet rays, the ceramic frit can be used to display aesthetically pleasing paint patterns on the glass. (A recent requirement by the vehicle manufacturers is to paint a third visor at the center of the windshield to eliminate the need for the top glass edge sunshade.)

Rear window defrosting frits can be found on a majority of all cars and have begun to appear on trucks as well. Rain sensor and light sensor devices are being added to an increasing number of vehicles. 

New glass technologies now offer the opportunity to cause the darkness of the glass to be modified either by passing an electrical current through the glass (electrochromic) or by utilizing the amount of ambient light to alter the darkness (photochromic).

New value-added requirements have also encouraged the return of laminated glass for non-windshield applications. New technology allows the glass to be heat strengthened (sort of half way between annealed and tempered) in rather thin sizes (1.7 to 2.1 mm). Laminating two pieces of this glass together reduces the noise level in the vehicle, cuts down on the amount of UV rays that enter and most importantly makes it extremely difficult to break into the vehicle.

Over the years, automobile manufacturers began adding another requirement for glass manufacturers—ease of installation on the assembly line. The initial requirements for the glass necessitated that it arrive at the assembly line with all the clips and attachments needed for installation. Many glass parts are encapsulated (either PVC or RIM) and primed (to accept the polyurethane application) prior to shipment to the car plants. Some automobile companies are using the “super plug concept” where entire door assemblies arrive just-in-time to be dropped into the door cavity as the vehicle passes by.

Many glass components are required to play an ever increasing structural role to help the vehicle safely withstand a rollover or other frontal or side collision. 
There is no doubt that OEM glass manufacturers will continue to be challenged to add even more functionality to glass as time goes on. Quality glass companies will also proactively step up with their new ideas that can be incorporated into futuristic vehicle designs. 

Russ Corsi recently retired as manager, technical services, from PPG Industries’ Automotive Replacement Glass business unit after 31 years in the glass industry. He now serves as a consultant to the industry. 

© Copyright 2005 Key Communications Inc. All rights reserved. No reproduction of any type without expressed written permission.