Windshield repair primarily relies on injecting a specialized resin into a chip or crack, which then cures to bond with the glass, effectively filling the damaged area and restoring its structural integrity; this resin is formulated to closely match the optical properties of the windshield glass, ensuring a seamless repair with minimal visibility of the damage; the key factors include the quality of the resin, the technician's skill in injecting it, and the use of specialized tools to create a strong bond and remove air bubbles from the crack. 

Key points about windshield repair science:

• Laminated glass composition:
  Windshields are made of laminated glass, consisting of two layers of glass bonded together with a plastic interlayer (usually Polyvinyl Butyral - PVB) which is crucial for its strength and ability to hold cracks together. 

• Resin properties:
  The repair resin is designed to have similar refractive index and adhesive properties to the windshield glass, allowing it to blend seamlessly with the existing glass. 

• Injection process:
  A technician uses specialized tools to carefully inject the resin into the damaged area, ensuring it reaches all the edges of the crack and displaces air. 

• Curing mechanism:
  Once injected, the resin is exposed to UV light which triggers a chemical reaction causing it to harden and bond with the glass. 

• Importance of technique:
  Proper technique is crucial for a successful repair, including cleaning the damaged area thoroughly, controlling the amount of resin injected, and ensuring complete curing. 

Factors affecting repairability:

• Crack size and location:
  Smaller chips and cracks located away from the edges of the windshield are generally more suitable for repair. 

• Severity of damage:
  Deep cracks or those with extensive spidering may require a windshield replacement instead of repair.