Silicone is the most common gluing agent for windshield repair. Silicone has a rubber-like consistency, which allows it to fill small cracks and even flexes with the movement of the glass. Silicone is also incredibly heat-resistant and does not dry out in the sun, so it will not lose its properties with time. Silicone is also very easy to apply. It works best when applied with a small toothpaste-like tube, rather than a syringe. Silicone is also odorless.