"Well what about rain, snow, and wind ?" I can hear you asking.
One word….
Goggles.
Back in the day our Grandfathers and Grandmothers were some tough, bug eating, dirt spittin' folks!
Just imagine driving in your car today without a windshield. The wind in your face, bugs up your nose, dirt in your teeth, while you scoot on down the road at high speeds. Sounds pretty uh……neat……huh?
As motorized vehicles grew in popularity and horsepower, their speed increased. Wind and road debris thrown into the faces of the drivers became a more serious matter. To alleviate this concern, vehicle manufacturers began including glass as, literally, a "wind shield".
Having a windshield in this day was a symbol of opulence and sent out a message of great wealth and prosperity. Having a windshield did not, however, protect the driver…in any way. These first windshields were hand cut from plate glass and were positioned at a relatively low position and allowed almost any rock easily to pelt the driver. A more serious, and potentially fatal problem with these plate glass windshields was they easily shattered into large, dangerously sharp pieces upon impact. More than one death by decapitation was recorded and later blamed on the windshield.
Yikes! Look out Grandpaw…..
In 1919 Henry
Ford of Ford automobiles addressed the windshield 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 of plastic 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.
Nowadays most windshield damage i.e. chips and small cracks, 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. Although we have PVB laminated glass nowadays, this willnot prevent a "ding" on your windshield. Dependant on the speed, weight of the rock, and angle of your windshield you may or may not be damaged. But here's the difference between you and your grisly death. Upon impact, even if the glass shatters, it sticks to the inner plastic laminate instead of showering the occupants with pieces of flying glass. Phew! 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, however, does not share the same properties. Around
1950, door glass and back glass changed to a tempered glass. It is
just one piece of glass that is sent into an atmospheric oven that
heats and quickly cools, or quenches the glass to harden it. This
tempered or “toughened” glass is also created with safety in
mind.. In an accident, or upon impact it crumbles into rounded benign
glass pebbles instead of shattering into large shards.
A collision or a large rock is not the only factor that can break a piece of your car glass however. Glass is very susceptible to quick changes in temperature.Have you ever put a hot windshield through a cold car wash, only to find it cracked when it is pulled out of the tunnel (at least its clean though). Rapid expansion and contraction will cause glass crack. This can also happen in the opposite scenario. Have you ever been in your vehicle on a cold winter day and turned on the defroster only to watch the crack expand before your very eyes?
No matter how it gets there, if you have either a 'ding' or cracked windshield, your safety is in jepardy. No! The windshield won't cave in on you, but having damage to your auto glass isn't exactly safe. When a car is first manufactured, the car must pass roll over tests, and as new technology lightened the weight of the vehicle, the windshield became an increasingly important factor in roll over safety.
Let me give you
an quick example of this that your science teacher might have used
back in elementary school. Take an egg. Place your two fingers on the
top with your thumb on the bottom of the egg. Now squeeze, squeeze
harder, squeeeeze ... 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.
Ok, don’t scramble your eggs just yet!
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 the 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 tempered glass is harder to break than a windshield, tempered glass can be very unstable. If the skin, or outer layer, is broken, it might explode in your face while you are driving. The reason for this product is in case of rollover. It is very difficult for authorities to cut through laminated glass. So if you are ever trapped inside your car, it is much easier to get through tempered glass than laminate.
Today’s windshields have made the evolution into complex, engineered auto 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'.
Bright
Idea!
Step 1:
Step 2:
Step 3:
Step 4:
Windshields, back glass and quarter
glass are mounted to the body of the vehicle against a mating flange
where the inner and outer body panels are sealed to each other.
First, the installer will fit the glass
to the opening to make sure the fit is snug and will not leak air or
water. An air gun can be a useful tool to determine air leakage. If
necessary, the windshield installer will continue to straighten the
body panel before refinishing. Next, the installer will use a
caulking gun and to apply the urethane adhesive. 
To use the windshield knife, the
installer will first remove outer moulding from the glass. Then the
knife is worked into place under the glass and it is drawn towards
the installer, steadily rocking back and forth while pulling on the
knife using "pull handle". The pull handle gives the
installer leverage. 
Caution:
