Exterior paint is more susceptible to problems than indoor paint because it gets more exposure to weather. Proper surface preparation and choosing the correct paint for the job are the solutions to most problems. Before you begin painting, look for signs of cracking, peeling, blistering, flaking, or mildew. If these problems aren't corrected before you begin, they'll crop up again after you've applied a fresh coat. Cracking, especially on wood or masonry surfaces, may be due to cracks in the surface beneath the paint. Scrape and sand down to the original surface and make repairs, if necessary. Clean the surface well, then use a primer before you apply fresh paint. Peeling often occurs on protected surfaces like overhangs. It's caused by chemicals that weren't completely washed off before painting. Again, scrape down to the original surface, wash thoroughly, and let it dry before applying a fresh coat. Blistering indicates a water problem. It could mean a leaky roof, or water entering the surface beneath the paint by some other means. Correct the moisture problem first; then let everything dry thoroughly before sanding and repainting. You might want to apply an undercoat first. Flaking, where the paint literally falls away from the surface, is actually the final stage of either a peeling or blistering problem. Mildew needs to be washed away with a solution of one part chlorine bleach to four parts water. Wear rubber gloves when you scrub it; then rinse the area thoroughly. Indoors, the biggest problem is generally bleed-through, when a stain or previous color comes through the new paint. Clean the area well, then apply an undercoat of shellac (* shel-LAK) to prevent this.
