Windshield damage repair methods

In the automotive industry, glass surfaces in vehicles have increased in recent years. Thus, glass has become a structural part of the vehicle, in addition to continuing to fulfill its initial function of allowing visibility and insulate the interior from the outside.

Before focusing on windshield repair it is extremely important to know the type of glass used in the car which is classified according to its functionality. The main features of the most representative type of glass are shown below.

Tempered glass. It is constituted by a single sheet of glass, of a thickness of approximately 5 mm, which is introduced in an oven, at a temperature between 500 and 750 ° C afterwards, is subjected to a rapid cooling. This treatment results in a more resistant and rigid glass. Due to the internal tensions produced in the glass, if a break occurs, it fragments into a multitude of small pieces. For safety reasons, this glass is no longer used on windshields, installed on side windows and on sunroofs.

Laminated glass. Its sand which configuration is integrated by two conventional sheets of glass, joined together by a central transparent plastic sheet of polyvinyl (PVB) or simply butyric. For safety, this type of glass is mandatory on windshields. In case of breakage, the polymer sheet keeps the glass in position, avoiding the risk of projecting glass particles or the expulsion of the occupants, while providing an emergency view to the driver.

Break in windshield

Generally, the breakage of the windshield may be due to two causes. The impact of an object at high speed (pebbles, gravel, etc.) or the transmission of tension or effort from the body itself.

The importance of damage caused by impact depends on several factors: size of the projected object against the windshield, subject matter, speed and angle of impact. The following are the most frequent notch types:

  1. Bull’s-eye. At the point of impact appears a small hole and below, a cone-shaped fissure, with the apex on the surface of the glass and its base on the plastic sheet. It is usually accompanied by a piece of detached glass, usually produced by the impact of a small stone.
  2. It is characterized by an impact point from which a series of radial fissures start. Its repair is usually a little more laborious, because you have to get the resin to penetrate all the cracks.
  3. The break is shaped like a daisy, with edges resembling petals. They are usually produced by small stones and their repair does not represent special difficulties.
  4. Half-moon. Caused by very small objects that crash into the windshield at high speed. They are small, C-shaped and have a tiny point of impact in their center.
  5. They present the characteristic impact of the type of ox eye or daisy, with radial fissures, like those of a star break.

Windshield repair is a process that combines technology and dexterity to fill a damaged area on the windshield with a transparent resin and adhesive (polymer). This resin (acrylic) is polymerized or cured by means of ultraviolet light of 365nm of wavelength. With this technique, the damaged area of ​​the windshield completely recovers its surface tension (its structural strength) and almost 100% of its clarity.

Repair techniques

Bursting. With the help of a punch, loose glass particles will be removed from the crater to facilitate penetration of the resin and to avoid imperfections. The technique of the repair consists in injecting the resin under pressure inside the rupture. For this purpose, specific injectors are used which, by means of the appropriate injector holder, are fixed to the glass, so that they are centered on the point of impact.

After removing the injector, a special cellophane lamella is placed on the break. This blade causes the resin to dry quickly with an ultraviolet lamp, in a time of 5 to 10 minutes, depending on the equipment and type of resin. Finally the resin will be polished to give it brightness and transparency, for it will be used the polishing liquid supplied with the equipment, which has added a very fine abrasive, usually cerium oxide powder.

Fissures. For the repair of a fissure it is advisable to drill a hole with a drill at a distance of 3 to 6 mm in front of the end or ends of the fissure to prevent it from spreading during the repair.

The injector is placed over the hole at the end of the crack and the resin is injected gradually, as if it were an infiltration. As the resin penetrates the rupture, are placed on the same, plastic sheets impregnated in the same resin to prevent it flies out, when the fissure is completely filled with resin is covered in its entire length with sheets Of plastic and curing with ultraviolet radiation and allowing it to act for 10 minutes, the excess resin is removed by scraping with the blade and making passes in a single direction. The repair is completed with a polishing and a final cleaning of the area.

It is of the utmost importance that landlords do not let too much time pass since the damage occurs. It will always be more advisable to repair rather than changing a damaged windshield while it is safe and feasible, this is because the original factory sealing of the windscreen to the body is retained, it is cheaper and faster so the unit is functional in a couple of hours If not in minutes.

Nowadays the incorporation of rain sensors, temperature, radio antennas, photochromic glasses, high-tech security systems … have considerably increased the cost of the windshields and it is here that again the repair is a more accessible solution.

Quality of repair

In order to repair windshields with satisfactory results it is necessary to have professional equipment, experience in the use of the same and a good knowledge of the best practices of the industry.

In the United States, windscreen repair professionals benefit from a voluntary standard that establishes appropriate practices and procedures.


  • Any repairs carried out in the area swept by the windscreen wiper should not reduce the effectiveness of the windscreen wipers. If any residual point remains after the repair, it should not exceed 5 mm in diameter. If it is located outside the critical viewing area; Or 2 mm, if it is totally or partially within the critical viewing area.
  • The repaired area must be free of air bubbles, foreign matter and craters or areas to be filled.
  • Repair should not change color over time.
  • Repair must restore the structural strength of the glass.