Cracked windshields are repaired using resin. Resin is made of acrylic acid. Think of resin as the glue that holds the crack together to prevent further damage. The type of resin you use depends on whether the crack in your windshield is small or large, shallow or deep.

Resin Viscosity

There are many types of resins on the market. If you are going to fix your windshield on your own, the first thing you must determine is the extent and depth of the damage. Then you need to choose your resin. It's all about the viscosity, or the thickness of the resin. Smaller, shallow cracks need a resin with less viscosity than larger, deeper cracks. Resin is measured in centipoise units, usually ranging between 20 to 200 cps. 

Small or Shallow Cracks

Small, shallow cracks often look more like chips in your windshield. This kind of damage commonly happens when loose gravel is kicked up by traffic. Although you can drive with a chipped windshield, getting it fixed will prevent larger cracks and possible windshield replacement. Resin with a lower viscosity works well on small chips and cracks that aren't deep. Look for a high-quality resin with a low cps.

Large or Deep Cracks

Larger and deeper cracks require a more viscous resin. Often the crack starts out small. Without repair, long cracks can begin to creep into your windshield. This kind of damage is commonly caused by larger chunks of road debris or hail. A high-quality, high-viscosity cps resin is thick and fills the voids left by the damage. The caveat is that most do-it-yourself kits are made for short, shallow cracks and chips. If your windshield damage exceeds eight inches, or is deep, consider replacement.

When to Hire a Pro

Resin is applied using a tool called an injector. After application, the resin must cure with either sunlight or a UV lamp. Many vehicle owners expect a flawless windshield after going through the resin process. Unfortunately, this is not the case. Resin simply keeps the existing chips and cracks from spreading. You will still see the damage. If you want a windshield with no chips and cracks, you will have to hire a windshield replacement professional.

Getting your windshield replaced is easy as there are many mobile windshield repair companies that will come to your location. Other vehicle owners may feel more comfortable making an appointment with their dealer or neighborhood mechanic. If you choose to DIY, choose your resin brand carefully. Ask questions about the process. A low-quality resin will not last, so you may need auto glass replacement anyway.