Parting agents such as talc and sand (or some combination thereof) are applied to
the top and back surfaces of the coated sheet from parting agent hoppers. These hoppers are
usually of an open-top, slot-type design, slightly longer than the coated sheet is wide, with a
screw arrangement for distributing the parting agent uniformly throughout its length. The first
hopper is positioned between the granule hopper and the first large press roller, and 8 to
12 inches. (0.2 to 0.3 m) above the sheet. It drops a generous amount of parting agent onto the
top surface of the coated sheet and slightly over each edge. Collectors are often placed at the
edges of the sheet to pick up this overspray, which is then recycled to the parting agent machine
bin by open screw conveyor and bucket elevator. The second parting agent hopper is located
between the rollers and dusts the back side of the coated sheet. Because of the steep angle of the
sheet at this point, the average fall distance from the hopper to the sheet is usually somewhat
greater than on the top side, and more of the material falls off the sheet (U.S. EPA, 1980).