How do long cracks start?
Over 90% of the time, long cracks start with a single chip close to the edge of your windshield. What’s most annoying is that the stone chip occurs in the black edge (the “frit”) of the glass, so you can’t see it until it has started to crack. Luckily, car windshield repair technology has advanced to the point where many of these long cracks can be repaired.
Why the edge of the glass?
That’s the weakest part of the windshield. The black “frit” is placed on the glass to keep the ultraviolet light from the sun from cooking the polyurethane seal that holds the glass to the frame of the vehicle. Otherwise, the seal would dry out, which could cause the windshield to leak, and to pop out in the event of an accident. But because it’s black, the frit gets very hot in the sun.
There is often a 20-30 degree difference in temperature between the center of your windshield and the edge. On a hot day, I’ve seen temperatures of 140F and higher on the edge of the glass! If you leave your car in the sun, over time this tends to make the edge of the glass brittle, and make it more susceptible to stone chips that turn into cracks.
Can anything be done about this?
There is a product on the market called “Edgeguard” which a couple of glass shops in town offer. It’s similar to the clear plastic bra material that you often see on new cars to prevent the paint from chipping, except that it is applied to the outside perimeter of the glass.
This product has proven to reduce greatly the amount of cracking that occurs from stone chips near the edge of the glass. Some dealers offer a guarantee that if your windshield does crack due to a stone chip near the edge of the glass, they will replace your windshield for you for free.
There are only two drawbacks to this product as far as I can see: cost, and visual attractiveness. The cost of applying Edgeguard is almost as much as buying a new windshield, which many people consider excessive. And after the product has been on the glass for awhile, it collects dirt around the edge, and visually isn’t very attractive.
Why should a crack be fixed promptly?
If a crack is more than about a month old, it tends to get dirty. The windshield wipers tend to push dirt into the crack over time. And when it rains, dirt is carried into the crack. So I generally shy away from doing a long crack repair if it is over 30 days old. However, if a crack is caught early enough, a good repair can be done that will accomplish three things:
- Stop the crack from spreading
- Restore much of the strength of the glass
- Make the crack look much less visible.
Or, as I say, we “stop it, make it stronger, and make it pretty!”
I have two (or more) separate cracks in my windshield. Can these be repaired?
Generally speaking, I won’t attempt to do a repair in this instance. A windshield with two or more cracks (or a complex crack, usually caused by a large rock or a baseball, for example) ought to be replaced, both from a visual and from a safety point of view.
What about Rain-X?
Rain-X, as you probably already know, is a liquid product that is applied to the outer surface of the glass to reduce the need for wipers during rain. Rain-X and similar products contain a wax or paraffin that causes the raindrops to bead up and then flow upward off the glass without the need for windshield wipers. A typical application lasts about six months.
The problem with Rain-X occurs if it gets into the crack. Because it is a wax, it reduces the ability of the resin that we use to bond the crack together. This makes a good strong repair nearly impossible.
That’s why I ask if you have used Rain-X or a similar product (ie, Aquapel) since the crack started. If so, then I can’t repair the crack.
What does a good long crack repair look like?
Even an excellent repair will still be visible. The best of repairs will look like a hair lying on top of the glass. After all, the glass has been damaged, and the crack won’t disappear. A good repair will greatly reduce the “glinting” that an open crack does when the sun hits it just right. If you look closely, at the tip of the crack you’ll see one or perhaps two little holes where resin has been inserted under pressure to keep the tip from growing.
A good crack repair won’t generally be noticed by someone walking by your vehicle in the parking lot, unless you point it out to them.
How strong is the car windshield repair?
There are no scientific analyses of the strength of long crack repairs that I am aware of. There is much anecdotal evidence, however, that shows that much of the original strength of the glass has been restored. In a rollover accident, for instance, the windshield becomes part of the passenger restraint system along with air bags. Photographs of such accidents with crack repairs prior to the accident show the windshield failing in other places than in the repaired area.
Much study needs to be done here to validate the improved strength of a crack that has been repaired. My “take” on such a repair in general is that it is better to repair the crack, rather than put it off.
Why bother with long crack repairs? Why not just get a new windshield?
There are at least two issues that my clients face when deciding about having me do a long crack repair: cost, and safety.
New windshields average over $300 now, with some high-end luxury vehicles having windshields that cost more than $1,000. My maximum cost to repair a crack, worst case, is $85.
Also, a replacement windshield may not be as safe as the original factory installation. I have seen litigation involving a windshield replacement company and an insured (or his insurance company) when the glass popped out during an accident due to poor installation.
However, a good replacement shop will give you a good safe installation. These shops will cost a little more, since they use the best glass available (yes, there are differences in quality of glass used in windshields), and the best polyurethane sealant. I am happy to refer you to a local windshield replacement company that does good work, and is competitive. And they’re good people.
Often it makes sense to get a new windshield because of the pitting and sandblasting of windshields that is so prevalent in Colorado. I’m finding that most windshields will last about two years before they need to replaced. I recently replaced a windshield in my own vehicle, and afterwards I felt like I’d been to the optometrist, it was so clean!
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