Fiberglass leaf patches are made of thermosetting resins or epoxies, which consist of 2 parts: resin and hardener. You mix these parts together to create a chemical reaction that internally creates heat so that the substance hardens over damage such as holes and cracks in fiberglass, steel and other nonporous surfaces. The kits include almost everything you will need to mend these surfaces yourself.
Clean the damaged area with a solvent like ethyl acetate or methyl ethyl ketone to remove residues like oil, dirt or grease. Solvents like acetone are highly flammable and may be toxic. Read product tags when using these goods and follow directions and safety precautions.
Rinse the region with clean water and let it dry completely.
Sand the area with coarse-grit sandpaper to at least 1 inch past the damage. If there are cracks, drill a small hole in the end of every crack. This prevents the break from expanding under the stain.
Smooth the area by sanding with fine-grit sandpaper, feathering it out in the border so the damaged region is level with the undamaged surface around it.
Wipe the area with a cloth dampened with alcohol.
Cut the fiberglass cloth included in your repair kit so that it matches over the area. Put the cloth over the region and tape the edges with masking tape to hold it in place.
Mix the resin and hardener in equal quantities on a sheet of cardboard or another disposable surface. Mix the two parts until you get a uniform color, but use only enough of each to complete the repair.
Apply the mixture to the fiberglass cloth utilizing the plastic spreader supplied with your kit. Expand it so that it’s evenly dispersed over the entire cloth.
Remove the masking tape and spread the mixture over the edges that are exposed.
Cover the mend with waxed paper or cellophane and leave the stain to cure overnight. Fiberglass leaf stain kits vary in drying period. Some cure in around three hours, while some require around 12 hours. Read the label to be certain you wait long enough for the repair to fully harden. If you’re able to make an impression in the patch with your thumbnail, then it is not fully healed.
Feather the edges and smooth the stain using fine-grit sandpaper like 220-grit. Smooth again with finer grit paper, like 320- to 600-grit, until the patch is level with the undamaged surface encompassing it.
Wait at least 12 hours after applying the stain to prime and paint the region to ensure the resin has fully healed.