paint is removed from brick work without destroying the dense , protective outer surface portion of the bricks by first scraping away heat - loosened paint and then lightly etching the brick surface to remove uniformly the paint residue by combined action of a high - velocity water stream and a relatively low - velocity , smaller stream of granular abrasive material directed at an angle into the water stream . the concentration of abrasive particles entrained in the water stream is varied while directing the water stream against the brick surface by moving the nozzle delivering the abrasive material stream closer to or farther from the water stream .