A watermark is made on a sheet of wet paper as it passes through a large roll during the paper making process. A watermark is a change of thickness in paper that creates a design or mark. The origin of watermarks is unclear, but they have been used as identification marks and decoration.
Dandy rolls are the large rolls that the wet paper is pushed through during the drying process of paper making. The dandy rolls have the watermark design imprinted on them; the mark is pressed into the paper, which makes the paper thicker and thinner in places to form the design. The design is only viewable when held up to a light. The earliest watermark can be traced to Bologna, Italy in 1282, but the exact origin and purpose of the watermark is unclear. Some paper manufacturers have used watermarks as the maker's trademark or identifying design to identify the size of the paper, the quality, the date the paper was made, or the location of the paper mill. While watermarks are still used to make counterfeiting more difficult, they are also used for decoration. There are two types of watermarks: the light and shade watermark, which creates more detail, and the wire watermark, which is marked by lines.