Power washing, or pressure washing, is the growing application of high pressure water spray. Produced by specially designed pumps, this spray is a hundred times more powerful than the typical garden hose. On concrete it is used to remove unsightly mold, bubble gum, and other dirt stains. Wooden decks are returned to the look of new wood, void of graying and fatigued finishes. And on houses, the appearance of siding (namely aluminum and vinyl) is greatly improved by removing pollution, mildew, and other signs of neglect.