How is a Windshield Repaired & When it Needs to Be Replaced?

Windshields are specifically designed to not only stand up to the stress that comes with driving on swarming highways but also provide structural support for the vehicle. When the outer layer of the windshield breaks, there is an inner PVB (Poly-Vinyl Butyral) layer of safety glass to hold the broken outer layer together in case of an accident. We have to thank the man behind that idea (to have 2 layers of glass sandwiching an inner layer of automotive safety glass) for being able to drive vehicles whose windshields do not fall apart when struck by objects.

So, now, one way or another, you ended up with anything from a small crack to a gaping hole in your windshield. And, now what? Is it repairable or should you go shopping for a replacement? Experts say that for small cracks, it is crucial to have them repaired the soonest possible so that they don’t get the chance to lengthen. For chips more than 2 inches, though, things look gloomy.

Repairing a Windshield

Automobile glazier repairs windshield of a car in auto service station garage

It usually doesn’t take more than half an hour to repair a crack or chip. However, it all depends on how deep that crack or chip is or whether there is dust accumulated into it. So, the first step is to remove debris and/or dust from the chip with a small vacuum. It is a very important step, and we really need to get rid of as much dirt as possible.

To restore the integrity of the windshield, a qualified auto glass repair technician usually injects resin into the outer glass layer. Then, the resin is cured and polished until the surface is smooth, with no bumps or unevenness. If it is done correctly, there is no way the chip or crack will cause further damage.

Of course, this procedure is performed when the windshield is considered to be repairable. If, for example, the PVB layer is damaged by a deep chip or crack, the technician will need to use a drill to make the hole more even and smoother. This will deepen the chip or crack and also make it slightly larger so that the resin can reach the PVB layer more effectively. With the help of an injector, which is attached around the treated area, small quantities of resin are injected into (and, in many cases, along too) the crack. Any excess resin is wiped off before the technician applies UV light to allow the resin to harden.

Repair it or Replace it?

Although most cracks and chips can be repaired, it depends on the size, location, depth, type, and severity of the damage done to the windshield. All these factors need to be carefully evaluated by the auto glass repair technician to determine whether the windshield is repairable or not.

1. Size & Depth

Most of the times, chips about 1 inch in diametre and cracks up to 3 inches long can be repaired. Until a few years ago, anything larger than that was considered unrepairable, and for some auto glass repair facilities, it still is. However, new technologies have emerged, making it possible to repair cracks larger than a dollar bill (and up to 18 inches long) and chips wider than an inch. So, it is all about the technician you choose and whether they have the expertise, equipment, and skills necessary to fix such cracks.

In general, cracks or chips that are no larger than a quarter can be repaired while multiple cracks are definitely more challenging.

Service agent  repairs danagerous crack in windhield on location without replacement glass

2. Location

Usually, cracks near the edge of the windshield compromises your safety, as well as the safety of everyone else in that car. The same applies to chips near the edge of the windshield that have caused it to start cracking. This is because the integrity, strength, and bonding of the windshield to the metal frame that surrounds it is jeopardised.

If the damage done is in the driver’s line of sight, any repairs will most likely reduce visibility and clarity to some extent. Repairs may also cause unevenness, discolourations, and mistiness. The technician will determine the line of sight of the particular vehicle based on the driver’s height and will then determine whether they can repair it with the means and know-how they possess.

Damages that cannot be repaired most of the times (we say “most of the times” because it all depends on the technological equipment and skilled technicians an auto glass repair facility has) are:

  • Deep damages that have occurred on both glass layers

  • Damage done on the inside of the windshield.

  • Damage that causes obstructed views that reduce the driver’s field of visions; hence, their ability to drive and make fast decisions in case of an accident.

  • Damages over the internal radio antenna or rain sensor.

  • Cracks that are longer than 18 inches.

  • Cracks that are contaminated.

  • Chips and cracks on the edge of the windshield.

  • Multiple cracks

Important Note: It is important the technician can see the chip or crack in its entirely (and clearly). In any other case, they might not be able to repair the windshield successfully.

3. Type of Cracks

Theer are many different types of cracks based on their shape

Most types of cracks occur from objects hitting the glass, such as rocks kicked up by the tires of a dump truck. Depending on where that object impacts the glass, we have a different type of crack. For example, when an object hits towards the centre of the glass, we usually have a starburst crack (many small cracks that spread out from the point of impact) while ones that strike the outside of the windshield, usually cause a long crack. There are also Bulls-eye cracks (caused by circular objects), Half-Moon cracks (aka Partial Bulls-Eye – damage is not completely circular), and Ding cracks (the crack that has the size of a quarter), among others, which can be easily repaired.

That aside, there are situations that can cause stress cracks on the windshield and don’t involve impact with another object. This can occur due to large variations in the temperature (i.e. a vehicle becomes overheated after long exposure to direct sunlight). For this reason, it is always best to melt or scrape ice off the windshield in the winter with cold water and not hot or warm. Stress cracks usually start at the edge of the windshield and don’t force glass to come off the windshield. This is why a technician with a ballpoint pen can easily figure out if a crack on a windshield is stress crack or not (they will run the pen along the crack, and if it doesn’t dip anywhere, it is a stress crack).

Final Notes:

  • Chips can quickly radiate into cracks so the sooner you seek professional help, the better. Delays may also cost you more money.

  • The most appropriate places to get your windshield repaired is a Same-OEM (Original Equipment Manufacturer) windshield or an OEM-Aftermarket substitute. You could also be offered an alternative glass that won’t abide by specific manufacturer guidelines.

  • Always allow an extra 60 minutes after your windshield is repaired before you hit the road again. This will allow the adhesives to bond and set.

  • Do some due diligence and check whether standards are followed.


Category: Auto Glass