The History Of Auto Glass: I Can See Clearly Now

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The automotive world is a hotbed for innovation and advancement. There are many systems and processes that have to work together to bring a vehicle off the factory floor and available to the public. Within each one of those systems has been countless hours of research design and improvement. We’re going to dig deep through the history of something you probably only think about when it is dirty or gets cracked: automotive glass.

Keeping the original markings and factory tint is important to the value of the vehicle.                   – Nick Fioto       ChopIt Kustoms

Early cars were motorized adaptations of horse drawn buggies. Open tops, barely chugging along down a rough trail. Many of the first windshields were flat pane windows, exactly like what would be used in a building.

For early automobiles, a windshield was an add-on option. When buying a new Ford Model T, a consumer could toss in an extra $100 to get a windshield, speedometer and headlights.

It wasn’t until 1915 when Oldsmobile was the first company to provide a windshield as standard equipment. Other manufacturers quickly followed suit.

Artist's rendering of plate glass production, circa 1900. Image: Corning Museum Of Glass

Artist’s rendering of plate glass production, circa 1900. Photo from Corning Museum Of Glass.

Windshields were developed out of practical reasons. First, windshields provided a wind block as well as acted to stop dirt and debris from hitting the occupants. Unfortunately, the plate glass that was being used would shatter into large chunks that could have disastrous result.

The windshield of this Model A took a substantial hit. Because it had an early form of laminated glass, the shards stayed together.

The windshield of this Model A took a substantial hit. Because it had an early form of laminated glass, the shards stayed together.

After multiple lawsuits due to bodily injuries, manufacturers pushed to improve the glass strength as well as lower costs. Henry Ford lead the charge, mostly due to the pressure of lawsuits against him and Ford Motor Company. The manufacturer started using a toughened glass, known as safety glass, that would shatter into harmless bits instead of large shards.

Example of broken safety glass.

Example of broken safety glass.

Advancements were still needed, however. Backing up to 1903, French Chemist Édouard Bénédictus stumbled upon an invention, entirely on accident. The story goes that his laboratory assistant failed to properly clean a glass jar after an experiment.

The glass jar had been coated with a clear cellulose nitrate substance that was virtually undetectable. The jar went back on to the shelf and happened to be the same jar that Bénédictus himself would later accidentally knock to the floor. When the glass jar hit the ground, it cracked but did not break into separate pieces.

Heat Strengthened Glass and how it breaks compared to Tempered Glass. Photo from PPG.com.

While Bénédictus was working on his glass, John C. Wood was working on his own in Great Britain. Wood originally started with tree resin, but later switched to a cellulose, sandwiched between two pieces of plate glass. Wood’s method was patented in 1905.

Though the two methods were essentially the same, Bénédictus received his patent in 1909. In 1910, Bénédictus added a gelatin layer that stuck to both panes of glass and created Triplex, which was then patented as well.

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Modern production of laminate glass. The sheet of PVB is laid between multiple layers of plate glass, then the entire unit is heated and cleaned. Photo from PPG.com.

In the 1920’s, Laminate Glass started to get used by automotive manufacturers for windshields, while keeping the rest of the windows as plate glass. Because the laminate glass stayed relatively intact after being broken, though spider web cracked, the glass actually helped increase the structural integrity of the vehicle. The car was now safer during a roll over and more likely to keep passengers from being ejected.

Pittsburgh Plate Glass (PPG). Image: Digital Common Wealth

Pittsburgh Plate Glass (PPG). Photo from www.digitalcommonwealth.org.

Around the late twenties, some automobile manufacturers began using laminate (safety) glass as a standard feature. Pittsburgh Plate Glass (PPG) developed an economical way to produce plate glass on a larger scale. Molten glass was fed through cooled rollers and pulled up to four stories high to cool and harden.

With their new process, PPG introduced their own version of safety glass, named Duplate in 1928. The same year, Ford advertised the use of Triplex in their vehicles. It wasn’t until 1937 when Federal regulations required the use of safety glass in all but the rear window, which continued through to the end of the fifties.

PPG launched Herculite in 1938. As a tempered glass, Herculite would crumble instead of shatter. Tempered glass was made by heating and then quickly cooling float glass. Tempered glass would go on to be widely used in non-windshield applications, even to this day.

Carleton Ellis solved a major issue with laminate glass in 1938. The cellulose between the panes would discolor after years in the sun. Ellis developed Polyvinyl Butyral (PVB) to be used instead of the cellulose that was clearer, stronger and helped block out harmful ultraviolet rays. PVB is still in use today.

Prior to the invention of PVB, the cellulose between the layers of glass would discolor and deform.

Prior to the invention of PVB, the cellulose between the layers of glass would discolor and deform.

The Libbey Owens Ford (LOF) Colburn sheet glass production line. Image: Google

The Libbey Owens Ford (LOF) Colburn sheet glass production line. Photo from University of Toledo.

Going through the forties, auto manufacturers started using large, single piece curved glass windshields. The Buick Special was the first to feature a full wraparound and panoramic windshield. The 1948 Tucker came with pop-out laminate glass windshields produced by Libby Owens Ford (LOF). Using a spongy rubber gasket, the windshields could be popped out of the vehicle in one full piece. The idea was to allow passengers a safe exit from a wrecked vehicle.

In 1959, the glass production world was revolutionized with the Pilkington Process, also known as the float glass process. Molten glass is evenly poured over a liquid metal bath, often times tin, to provide consistent thickness and an ultra-smooth surface. Float glass is considered modern glass. Float glass is used for both laminated and tempered glass.

Pilkington purchased Triplex in 1972 and then in 1986 purchased Libby Owens Ford. Pilkington and PPG continue to this day as leading glass producers for automotive and architectural applications.

Vehicle safety became a huge public concern in the sixties. The National Highway Traffic Safety Administration was formed in 1970 by the Federal Government to regulate safety requirements of new vehicles. Many of the laws they have created concern the glass used in vehicles.

Types Of Automotive Glass

Sheet Glass – Molten glass that has been forced through rollers to the desired thickness, air cooled and then cut to size. Recognizable by distinctive wavy lines. Used mostly for homes, though very early automobiles did use it some.

Plate Glass – Rolled molten glass that has been polished to remove distortions, then cut to size.

Float Glass – Made by pouring molten glass over a liquid metal bath. The glass floats to the top and cools with no distortions, eliminating the need for polishing.

Laminated Glass – Also known as safety glass. Made up of two or more panes of glass with a clear bonding material between them. Allows the glass to crack but not fall apart. Used in primarily for windshields.

Tempered Glass – Float glass that has been reheated and cooled rapidly. Very strong but when it does break, it crumbles into very small pieces. Used in most non-windshield auto glass applications.

The history of auto glass is convoluted. There have been a lot of advancements, company changes and buzz words used in ads that mix up the whole batch. Knowing the differences between the types of glasses used in automobiles is the first step to properly evaluating a classic car. Depending on the goal of the project, the type of glass used in the windshield, side glass and rear window can be the difference between a perfect reproduction or a modern touring car.

Many manufacturers used different glasses through the years and even models of their vehicles. Today’s internet age allows us to look into the past and find the exact right glass. Previously, this information was acquired from books like the National Auto Glass Specifications by M. H. Tracy. These books contain all the details of what glass was used in the vehicle, including dimensions and glass type. Additionally, books like the Chilton Automobile Directory were indispensable in finding manufacturers that built components all around the country.

nationalautoglassspecs01

The Chilton Automobile Directory was the go-to place to find any manufacturer in the United States that was building components for automobiles.

Window stamps and markings are an easy way to know if a piece of glass is original to a vehicle or not. Many manufacturers put the OEM mark directly into the glass, though there was no requirement to do so.

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Various window stampings/markings.

When discussing auto glass with industry professionals, often times it comes down to just making sure the glass fits well and looks good. Jeff Hyman, primary appraiser for Classic Auto Appraisers in Irvine, California, agrees. “It’s not typically part of the numbers matching components we look for,” Hyman explains. When dealing with a Concours d’Elegance (all original, down to the very last bolt), then there may be some requirements. Often times though, it just needs to have the correct stamp. Classic Auto Appraisers recently appraised a 1963 Corvette with a split windshield that had been replaced. The window stamp had been etched into a new piece of glass because original units were no longer available.

Duplate window stamp on a Henry J.

Duplate window stamp on a Henry J.

Nick “ChopIt Jr.” Fioto of ChopIt Kustoms in Orange, California has built many customs over the years he has spent in the shop. Chop tops, full custom builds and far out modifications have kept him on his toes. When it comes to glass, Nick tries to use the original pieces as much as possible. “Especially the curved pieces,” says Nick. “Keeping the original markings and factory tint is important to the value of the vehicle.” Additionally, reusing the original glass helps to save the customer costs, allowing for those funds to go elsewhere in the build if they want. When ChopIt Kustoms does need to get new or custom flat glass made, they have a local glass company cut it for them using laminate sheets.

The appraiser doesn’t put a whole lot of stock into original glass for many applications and the builder puts emphasis on it. This is a classic difference we see throughout all of the hot rodding industry. For instance, some builders have no issue with putting a Chevy power plant in a Ford while others find it sacrilege. It all greatly depends on the end goal of the build or rebuild.

The 1954 Buick Special was the first production vehicle to feature a full wraparound and panoramic windshield. Photo from www.pinterest.com.

In the Boca Raton Concours d’Elegance, glass falls within the Exterior section. Over all, the exterior is worth 40 points. The overall exterior is judged using the objective criteria’s of authenticity, condition, and appearance. The glass is only a small portion of the many things in the section. There is certainly more bodywork than glass, though missing a stamp or having the incorrect stamp could be the difference between winning and losing.

Ultimately, your glass choice is going to come down to you and your build. Whether building a radical chop top or restoring your car to compete at Pebble Beach, you’ll need to make some choices of what is important to you. At least now you have a bit more understanding of the how’s and why’s of automotive glass.

About the author

Jake Headlee

Jake's passion started at a young age wrenching on cars with his Dad. Obtaining that glorious driver's license sparked his obsession with grease and horsepower, and the rest is history. Soon, he was a general mechanic and suspension specialist, and currently designs and modifies products for the off-road industry. Jake enjoys rock crawling, desert racing and trail running, and writing in his spare time.
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