Is frost accumulating inside your windows? Try this trick. Dissolve 2 teaspoons of salt in a gallon of water, then use a rag to wipe down the insides of your windows and windshield with the mixture. Don not use it on the car’s exterior because the salt could corrode exposed metal. As the solution dries, it will leave an invisible layer of salt which, thanks to its low freezing temperature, will help keep frost from forming for a full month or more.