A windshield is generally considered to be part of an automobile's body, something that serves its purpose until broken, cracked or damaged by impact. In fact, a glass windshield is vulnerable to gradual deterioration as a car ages.
Small particles of sand can pit and crater a windshield, degrading visibility and reducing the effectiveness of windshield wipers.
Although the glass may appear transparent enough to serve its purpose most of the time, badly pitted windshields are a safety hazard. If sunlight hits the windshield at an oblique angle, it can cause the windshield to blank out like a television screen and reduce visibility to zero.
I am frequently asked by readers if there is product or service that repairs such damage. After extensive checking with a number of nationwide auto-glass repair shops and with trade organizations representing glass manufacturers, I found that there is no widely accepted prescription.
Pitting of windshield glass is a significant problem in desert areas, where blowing sand creates extreme abrasive conditions, and in colder climates, where sand or gravel is applied to icy roads.
Although many motorists consider glass to be a hard substance, it is quite soft. Sandpaper, for example, can easily scratch tempered glass.
Auto windshields are made with two layers of glass with a vinyl laminate in the middle. The laminate holds the glass together so occupants won't get sprayed with fragments in a collision. In other areas of the car, toughened safety glass is used; it is designed to shatter into dull-edged pieces. Each type of glass transmits about 80% of visible light.
Some independent repair shops will polish glass with special rouge compounds to alleviate pitting. This method is not approved by technical organizations in the glass business, however, and many repair firms have refrained from using it. Neither the National Glass Assn. nor the Society of Automotive Engineers could identify an acceptable repair procedure for worn glass.
One problem is that the quality of such restorations is uneven at best. An even more significant problem is that there are no standards for what is considered unacceptable pitting and therefore what would represent an acceptable repair. Most states have no safety regulations concerning pitted glass.
The only way to correct a badly pitted windshield is to replace it. The average cost of a new windshield is $200. Special windshields, like those with special defogger elements or complex contours, can cost more than $1,000.
If a windshield is not pitted but has minor cracks, holes or scratches, it often can be repaired.
Several systems offered by franchise glass dealers can fuse cracks so that they are nearly invisible. One system, offered by U.S. Auto Glass Centers and USA-Glas Network, uses a resin bonding agent that is cured with ultraviolet light. The damaged part is drilled out, a transparent liquid resin is injected, and the compound is cured with ultraviolet light. The repair costs about $40.
In addition, small holes caused by rocks can be filled and polished. In most cases, these repairs are performed only in areas outside the driver's critical viewing area.
Finally, many auto insurers will begrudgingly pay for windshield replacements, because in many cases cracks or pitting can be attributed to road damage.