You can put clear nail polish on solar lights. This is a quick and easy method to fix solar lights. You just need to apply only a small amount of clear nail polish evenly over the solar cells. Allow the nail polish to dry completely before using the light. This method works for all kinds of solar lights such as string lights, pathway lights, and garden lights. It also works on Christmas solar stake lights so make sure you have plenty of clear nail polish on hand so you can revive them before Christmas!