Watermarks are an integral part of some papers. They are formed in the process of paper manufacture. Watermarks consist of small designs, formed of wire or cut from metal and soldered to the surface of the mold or, sometimes, on the dandy roll. The designs may be in the form of crowns, stars, anchors, letters or other characters or symbols. These pieces of metal – known in the paper-making industry as “bits” – impress a design into the paper. The design sometimes may be seen by holding the stamp to the light. Some are more easily seen with a watermark detector. This important tool is a small black tray into which a stamp is placed face down and dampened with a fastevaporating watermark detection fluid that brings up the watermark image in the form of dark lines against a lighter background. These dark lines are the thinner areas of the paper known as the watermark. Some watermarks are extremely difficult to locate, due to either a faint impression, watermark location or the color of the stamp. There also are electric watermark detectors that come with plastic filter disks of various colors. The disks neutralize the color of the stamp, permitting the watermark to be seen more easily.
Some inks used in the photogravure process dissolve in watermark fluids. Also, see “chalky paper.” Watermarks may be found normal, reversed, inverted, reversed and inverted, sideways or diagonal, as seen from the back of the stamp. The relationship of watermark to stamp design depends on the position of the printing plates or how paper is fed through the press. On machine-made paper, watermarks normally are read from right to left. The design is repeated closely throughout the sheet in a “multiple watermark design.” In a “sheet watermark,” the design appears only once on the sheet, but extends over many stamps.
Individual stamps may carry only a small fraction or none of the watermark. “Marginal watermarks” occur in the margins of sheets or panes of stamps. They occur on the outside border of paper (ostensibly outside the area where stamps are to be printed). A large row of letters may spell the name of the country or the manufacturer of the paper, or a border of lines may appear. Careless press feeding may cause parts of these letters and/or lines to show on stamps of the outer row of a pane.
Source: Scott Stamp Catalogue
Avneesh Stamp Collection 