To apply Flex Seal, shake the can, and spray the sealant in a sweeping motion at a 12- to 14-inch distance from the object. Apply several coats, shaking the can periodically throughout application.
Apply several even coats of the sealant until holes and cracks no longer remain visible, allowing the surface to dry completely between each coat. Flex Seal dries in two to three hours, but it requires 24 hours to cure completely. For best results, only use the sealant if the can remains above 60 degrees Fahrenheit, and invert the nozzle to spray a short burst when you are done. Always use Flex Seal in a ventilated area while wearing protective clothing, and open doors and windows to prevent vapor buildup. Do not apply the sealant near ignition sources such as pilot lights.
A large can of Flex Seal can cover 2 to 8 square feet, while a jumbo can covers 2 to 12 square feet. If sealing a large surface area, use no more than half of the can at once, waiting one hour before continuing to allow the sealant to dry and the vapors to dissipate. Flex Seal adheres to metal, plastic, glass, wood, cement, dry wall and a variety of other surfaces. The sealant works best when used on clean, dry surfaces.