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A watermark is a recognizable image or pattern in paper that appears as various shades of lightness/darkness when viewed by transmitted light (or when viewed by reflected light, atop a dark background), caused by thickness or density variations in the paper.^[1] There are two main ways of producing watermarks in paper; the dandy roll process, and the more complex cylinder mould process.

Watermarks vary greatly in their visibility; while some are obvious on casual inspection, others require some study to pick out. Various aids have been developed, such as watermark fluid that wets the paper without damaging it. Watermarks are often used as security features of banknotes, passports, postage stamps, and other documents to prevent counterfeiting.

A watermark is very useful in the examination of paper because it can be used for dating, identifying sizes, mill trademarks and locations, and the quality of a paper.

Encoding an identifying code into digitized music, video, picture, or other file is known as a digital watermark.

Dandy roll process

A watermark is made by impressing a water-coated metal stamp or dandy roll onto the paper during manufacturing. These watermarks were first introduced in Bologna, Italy, in 1282;^[2] however the dandy roll was invented in 1826 by John Marshall. Watermarks have been used by papermakers to identify their product, and also on postage stamps, currency, and other government documents to discourage counterfeiting. In France, they were introduced during World War II by the Vichy regime, and counterfeited by people such as Adolfo Kaminsky. The invention of the dandy roll revolutionised the watermark process and made it much easier for a company to watermark their paper.

The dandy roll is a light roller covered by material similar to window screen that is embossed with a pattern. Faint lines are made by laid wires that run parallel to the axis of the dandy roll, and the bold lines are made by chain wires that run around the circumference to secure the laid wires to the roll from the outside. Because the chain wires are located on the outside of the laid wires, they have a greater influence on the impression in the pulp, hence their bolder appearance than the laid wire lines.

This embossing is transferred to the pulp fibres, compressing and reducing their thickness in that area. Because the patterned portion of the page is thinner, it transmits more light through and therefore has a lighter appearance than the surrounding paper. If these lines are distinct and parallel, and/or there is a watermark, then the paper is termed laid paper. If the lines appear as a mesh or are indiscernible, and/or there is no watermark, then it is called wove paper. This method is called line drawing watermarks.

Cylinder mould process

Another type of watermark is called the cylinder mould watermark. A shaded watermark, first used in 1848, incorporates tonal depth and creates a greyscale image. Instead of using a wire covering for the dandy roll, the shaded watermark is created by areas of relief on the roll's own surface. Once dry, the paper may then be rolled again to produce a watermark of even thickness but with varying density. The resulting watermark is generally much clearer and more detailed than those made by the Dandy Roll process, and as such Cylinder Mould Watermark Paper is the preferred type of watermarked paper for banknotes, passports, motor vehicle titles, and other documents where it is an important anti-counterfeiting measure.

Watermarks on postage stamps

Elephant head watermark used on early stamps of India.

In philately, the watermark is a key feature of a stamp, and often constitutes the difference between a common and a rare stamp. The "classic" stamp watermark is a small crown or other national symbol, appearing either once on each stamp or a continuous pattern. Watermarks were nearly universal on stamps in the 19th and early 20th centuries, but generally fell out of use and are not commonly used on modern issues.

Some types of embossing, such as that used to make the "cross on oval" design on early stamps of Switzerland, resemble a watermark in that the paper is thinner, but can be distinguished by having sharper edges than is usual for a normal watermark.

References

^ Biermann, Christopher J. (1996). "7". Handbook of Pulping and Papermaking (2 ed.). San Diego, California, USA: Academic Press. p. 171. ISBN 0-12-097362-6.
^ Meggs, Philip B. (1998). A History of Graphic Design (Third ed.). John Wiley & Sons, Inc. p. 58. ISBN 978-0471291985.

External links

Watermarks in databases and other watermark projects:

Bibliography on watermarks and papers in Greek manuscripts:

http://abacus.bates.edu/Faculty/wmarchive/Bibliography.html

[1] Biermann, Christopher J. (1996). "7". Handbook of Pulping and Papermaking (2 ed.). San Diego, California, USA: Academic Press. p. 171. ISBN 0-12-097362-6.

[meggs58-2] Meggs, Philip B. (1998). A History of Graphic Design (Third ed.). John Wiley & Sons, Inc. p. 58. ISBN 978-0471291985.

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 == Dandy roll process ==
-A watermark is made by impressing a water-coated metal stamp or ''dandy roll'' onto the [[paper]] during manufacturing. These watermarks were first introduced in [[Bologna]], [[Italy]], in 1282;<ref name="meggs58">{{Cite book | last = Meggs | first = Philip B. | authorlink = Philip B. Meggs | title = A History of Graphic Design | publisher = John Wiley & Sons, Inc. | date = 1998 | location =  | edition = Third | pages = 58 | isbn = 978-0471291985}}</ref> however the dandy roll was invented in 1826 by John Marshall. Watermarks have been used by papermakers to identify their product, and also on [[postage stamp]]s, [[currency]], and other government documents to discourage [[counterfeit]]ing. The invention of the dandy roll revolutionised the watermark process and made it much easier for a company to watermark their paper.
+A watermark is made by impressing a water-coated metal stamp or ''dandy roll'' onto the [[paper]] during manufacturing. These watermarks were first introduced in [[Bologna]], [[Italy]], in 1282;<ref name="meggs58">{{Cite book | last = Meggs | first = Philip B. | authorlink = Philip B. Meggs | title = A History of Graphic Design | publisher = John Wiley & Sons, Inc. | date = 1998 | location =  | edition = Third | pages = 58 | isbn = 978-0471291985}}</ref> however the dandy roll was invented in 1826 by John Marshall. Watermarks have been used by papermakers to identify their product, and also on [[postage stamp]]s, [[currency]], and other government documents to discourage [[counterfeit]]ing. In [[France]], they were introduced during [[World War II]] by the [[Vichy France|Vichy regime]], and [[identity document forgery|counterfeited]] by people such as [[Adolfo Kaminsky]]. The invention of the dandy roll revolutionised the watermark process and made it much easier for a company to watermark their paper.
 The ''dandy roll'' is a light roller covered by material similar to [[window screen]] that is embossed with a pattern. Faint lines are made by ''laid wires'' that run parallel to the axis of the dandy roll, and the bold lines are made by ''chain wires'' that run around the circumference to secure the laid wires to the roll from the outside. Because the chain wires are located on the outside of the laid wires, they have a greater influence on the impression in the pulp, hence their bolder appearance than the laid wire lines.