History of Auto Glass
Prior to 1919, “horseless carriages” were very few in
number and operated at relatively low speeds. When they first appeared
on the scene, they weren’t equipped with windshields. For protection
against bad weather, insects, and other road debris, drivers and
passengers alike used goggles. Just imagine driving in your car today
without a windshield. The wind in your face, blowing through your
hair, while you wisss down the road at high speeds. Sounds pretty
neat huh.
As motorized vehicles grew more common and their speed increased,
the wind and debris thrown into the faces of drivers became a more
serious matter. To alleviate this concern, manufacturers included
glass as, literally, a wind shield. While the new windshields made
the drive more comfortable, they did not adequately protect from
flying debris. These first windshields were hand cut from plate glass.
The problem with these plate glass windshields was they easily shattered
into large, dangerously sharp pieces upon impact.
In 1919 Henry Ford addressed the problem by using a new technology,
developed in France, called glass laminating. Windshields made using
this process were actually two layers of glass with a cellulose inner
layer that held the glass together. Between 1919 and 1929 Ford ordered
the use of laminated glass on all of his vehicles.
Today, windshields are no longer held together with cellulose, but
with a high-strength vinyl called polyvinyl butyral (PVB). This type
of glass is ideal for automobile windshields because of it's strength
and reliability.
Today most windshield damage is caused by small rocks that get caught
between the treads of vehicle tires. As the car builds up speed these
rocks are flung into the air... and onto your windshield. When this
happens the glass, depending on the angle of the hit and how fast
you are going, can become 'dinged'. Upon impact, even if the glass
shatters, it sticks to the inner plastic laminate instead of showering
the occupants with pieces of flying glass. The laminated glass also
provides a cushioning effect during collisions. Because of its strength,
this plastic layer absorbs much of the shock upon impact and keeps
the occupants from being ejected through the windshield.
The glass in the rest of the car is different.
Around the 1950's the door glass and the back glass changed to
a tempered glass. It is just one piece of glass that is sent into
an atmospheric oven that heats and quenches the glass to harden
it. This tempered or “toughened” glass
is also considered safety glass. It is strengthened through the application
of heat and pressure. Upon impact it crumbles into rounded glass
pebbles instead of shattering into large dangerous pieces.
Glass is very susceptible to quick changes in temperature. Rapid
expansion or contraction will cause it to crack. This can happen
in the winter when your defroster rapidly heats a frozen windshield,
or in summer when a hot windshield comes in contact with the cold
water of a car wash.
No matter how it gets there, if you have either a 'ding' or cracked
windshield, your safety is being compromised. Even though the windshield
won't cave in on you, it isn't exactly safe. All cars must pass roll
over tests, and as the car manufacturer lightened the weight of the
vehicle, they made the windshield an important factor in roll over
safety. If you have a cracked, or 'dinged' windshield you are compromising
the structural integrity of your vehicle.
Let me give you an example of this that your science teacher might
have used back in school. Take an egg. Place two fingers on the top
with your thumb on the bottom of the egg. Now squeeze with all your
might... what happened... nothing right? Mother nature created the
perfect non-breakable structure so when the mother hen sat on her
nest the eggs wouldn't break. Okay... now take a needle and poke
a hole in the egg... you have just compromised it's structural integrity.
Next, hold the egg in your hand like before and squeeze hard... :-)
You probably have egg all over your hand... right? If your windshield
has a crack or rock chip in it, the structural integrity has been
compromised much like the egg with a needle hole in it.
The good news is that laminated safety glass can usually be repaired,
however, while scratches can be buffed from tempered glass, it cannot
be repaired. The reason for different types of glass in vehicles
today is safety. We can not have tempered glass for windshields on
the roads in the United States. Although harder to break than a windshield,
tempered glass can be very unstable. If the skin is broken, it might
explode in your face while you are driving. The real reason for this
product is in case of rollover. It is very difficult to cut through
laminated glass. So if you are ever trapped in your car, its easier
to get through tempered glass than laminate.
Today’s windshields have evolved into complex, engineered
glass systems with heating elements to melt ice, or, coatings to
repel ultra-violet radiation. Shade bands, radio & telephone
antennas, satellite uplinks, heads-up holographic instrument displays,
or even sensors to activate windshield wipers or close convertible
tops are now common.
The modern windshield is also thinner and lighter to reduce overall
vehicle weight and thereby contribute to increased fuel economy.
In short, consumer demands have influenced engineers to design enhancements
into the glass and, in so doing, have made windshields more costly
to produce.
Increased windshield performance comes at
the cost of higher prices. In the early 1990's, increased prices
created an economic incentive to repair rather than replace windshields.
Prior to 1990, fewer than 500,000 damaged windshields were repaired
every year. Today millions of Americans chose repair annually.
The reason… average windshield
replacements cost between $250 and $1,000; the average repair is
between $50 and $75, depending on the number of 'dings'. |
