A term referring to the impression of a design, pattern or symbol in a sheet while it is being formed on the paper machine wire. It appears in the finished sheet as either a lighter or darker area than the rest of the paper. Two types of watermarks are available. A shaded watermark is produced by a dandy roll located at or near the suction box on the Fourdrinier. The desired design is pressed into the wire covering the surface of the dandy roll similar to an intaglio engraving. As the wet pulp moves along the web the dandy roll presses down and creates an accumulation of fibers, thus the watermark is seen as being darker than the rest of the sheet.
The second type of watermark, called a wire mark, is accomplished by impressing a dandy roll with a raised surface pattern into the moving paper web in a similar manner to the shaded mark. This creates an area with less fiber making it lighter and more translucent.
Watermarks come in a variety of placement styles. Random, the least expensive to create, is a watermark that appears repetitively throughout the sheet in no particular order. A localized watermark is one that appears in a predetermined position on each sheet. Paraded watermarks appear in a line, either vertically or horizontally on each sheet. A staggered watermark pattern consists of several watermarks on each sheet in a predetermined fashion. (See dandy roll)
