Cracks and chips occurring in your windscreen are an annoying but inevitable part of driving, and having windscreen damage repaired as soon as possible is always of vital important. The windscreen doesn't just protect you from road wind and the occasional suicidal bug -- they also form a key structural component that gives your vehicle rigidity, and running with a compromised windscreen for too long can cause more widespread (and expensive) damage to your car, truck or ute.
However, while modern windscreen repair methods and technologies are enormous effective there is only so much they can do, and some types of windscreen damage can make windscreen replacement a more practical and affordable prospect than repairs. The following types of windscreen damage are notoriously difficult to fix, and may require your windscreen to be replaced entirely before you can get back on the road safely:
Neglected cracks and chips
The longer a crack or chip in your windscreen is left unrepaired, the more difficult it will be to fix. If left exposed while driving, a crack or chip will accumulate dirt and detritus within its cracks, causing it to become contaminated and reducing the effectiveness of glass resins and other repair compounds.
This doesn't mean you should take your car off the road the moment your windscreen suffers damage, and most cracks and chips can be effectively repaired after a few days or weeks of exposure. However, cracks left for longer can become impossible to repair as the detritus becomes firmly entrenched within the damaged glass -- in these cases, wholesale windscreen replacement is often required.
Damage in the driver's eye line
Modern windscreen repairs are far less noticeable than they once were, but a repaired crack or chip still creates discolouration and unevenness in the glass which can form a distraction or make the windscreen more difficult to see through clearly. Aging repair jobs can be particularly noticeable, as windscreen repair resins have a tendency to yellow over time as a result of UV exposure.
If these repaired cracks and chips are located on the passenger's side of the windscreen, or around the edges and corners of your windscreen, they can generally be ignored, safely. However, cracks and chips directly in the driver's eye line may form an unacceptable visual block or distraction even if thoroughly repaired, and significant damage to the drivers side of the windscreen may necessitate full replacement.
Damage that penetrates the windscreen
Vehicle windows are not made from conventional glass but laminated glass, a unique product that consists of a transparent level of vinyl sandwiched between two thin sheets of tempered glass. This robust structure gives car windscreens and windows their characteristic toughness, and prevents dangerous shattering in the event of an accident.
However, the properties of laminated glass can become more of a hindrance than a help when it comes to repairing penetrative damage to your windscreen. Damage that has affected both sheets of glass is far more difficult to repair, as windscreen repair processes can only work on one side at a time, and the process of repairing one side of a penetrative crack may worse the damage sustained by the other side. Even if these cracks and chips can be acceptably repaired, they generally leave behind a very visible mark that can become distracting, so full windscreen replacement should be seriously considered.