Rain Proof is an additive that will make your resin miscible with water so you can do repairs with water in the break. Do not let rain or snow interfere with your business and save yourself from the time consuming task of drying out breaks with heating devices that can crack the windshield. Simple add one drop into your injector with three to five drops of resins and stir (toothpick works best) and your resin is waterproof.