Keeping up Appearances

When aqueous coatings dry too fast and become brittle, fine lines may appear, ranging in size from 1⁄64˝ to 3⁄4˝. According to Dennis Oscar, Water Base Coatings product manager for Northwest Coatings, "cracking" usually occurs over heavy process colors, and can often be eradicated by putting slightly more coating down and by lowering the stack temperature. He adds, "If these measures do not work, 0.25 percent to 0.50 percent of propylene glycol can be added to the coating to make it more flexible." The addition slows the dry rate of the aqueous coating while increasing its tendency to block.