in figure 8-5. The root cause of most blistering, otherthan that caused by excessive heat, is inadequateventilation plus some structural defect allowingmoisture to accumulate under the paint. A primesource of this problem, therefore, is the use ofessentially porous major construction materials thatallow moisture to pass through. Insufficient dryingtime between coats is another prime reason forblistering. All blisters should be scraped off, the paintedges feathered with sandpaper, and the bare placesprimed before the blistered area is repainted.Prolonged TackinessA coat of paint is dry when it ceases to be“tacky” to the touch. Prolonged tackiness indicatesexcessively slow drying. This may be caused byinsufficient drier in the paint, a low-quality vehicle inthe paint, applying the paint too thickly, paintingover an undercoat that is not thoroughly dry,painting over a waxy, oily, or greasy surface, orpainting in damp weather.Inadequate GlossSometimes a glossy paint fails to attain thenormal amount of gloss. This may be caused byinadequate surface preparation, application over anundercoat that is not thoroughly dry, or applicationin cold or damp weather.Figure 8-5.—Blistering.IMPROPER APPLICATIONOne particular area you, as a Builder, havedirect control over is application. It takes a lot ofpractice, but you should be able to eliminate the twomost common types of application defects: crawlingand wrinkling.CrawlingCrawling (fig. 8-6) is the failure of a new coatof paint to wet and form a continuous film over thepreceding coat. This often happens when latex paintis applied over high-gloss enamel or when paints areapplied on concrete or masonry treated with asilicone water repellent.WrinklingWhen coatings are applied too thickly,especially in cold weather, the surface of the coatdries to a skin over a layer of undried paintunderneath. This usually causes wrinkling (fig. 8-7).Wrinkling can be avoided in brush painting or rollerpainting by brushing or rolling each coat of paint asthinly as possible. In spray painting, you can avoidwrinkling by keeping the gun in constant motion overthe surface whenever the trigger is down.PAINT DEFECTSNot all painting defects are caused by theindividual doing the job. It sometimes happens thatthe coating itself is at fault. Chalking, checking, andcracking are the most common types of productdefects you will notice in your work as a Builder.Figure 8-6.-Crawling.8-12
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