This "Crown & CA" (for "Crown Agent") watermark was standard for postage stamps of the British colonies from the 1880s to the 1920s.

A watermark is a recognizable image or pattern in paper that appears lighter when viewed by transmitted light (or darker when viewed by reflected light, atop a dark background). Paper is thin material mainly used for writing upon printing upon or packaging There are two main types of watermark, the Dandy Roll process, and the more complex Cylinder Mould process. 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. Questioned document examination (QDE is the forensic discipline pertaining to documents that are (or may be in dispute in a court of law

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. Encoding an identifying code into digitized music, video, picture, or other file is known as a digital watermark. Music is an Art form in which the medium is Sound organized in Time. Video is the technology of electronically capturing, Recording, processing storing transmitting and reconstructing a sequence of Still images An image (from Latin imago) or picture is an artifact usually two-dimensional that has a similar appearance to some subject &mdashusually Digital watermarking is the process of embedding information into a digital signal

The Dandy Roll Process

A Dandy Roll watermark is made by impressing a water-coated metal stamp or dandy roll onto the paper during manufacturing. Paper is thin material mainly used for writing upon printing upon or packaging These watermarks were first introduced in Bologna, Italy in 1282; they have been used by papermakers to identify their product, and also on postage stamps, currency, and other government documents to discourage counterfeiting. Bologna (boloɲa from Latin Bononia, Bulåggna in Bolognese dialect is the capital city of Emilia-Romagna in northern Italy Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest A postage stamp is an adhesive paper evidence of pre-paying a fee for postal services A currency is a unit of exchange, facilitating the transfer of Goods and/or services It is one form of Money, where money is A counterfeit is an imitation that is made usually with the intent to deceptively represent its content or origins

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. Wood pulp is a dry fibrous material prepared by chemically or mechanically separating the fibers which make up Wood. Fiber or fibre is a class of Materials that are continuous filaments or are in discrete elongated pieces similar to lengths of thread. Because the patterned portion of the page is thinner, it transmits more light through and therefore has a lighter appearance than the surrounding paper. A page is one side of a leaf of Paper. It can be used as a measurement of Documenting or Recording quantity ("that topic covers twelve pages" Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 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.

The 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. Year 1848 ( MDCCCXLVIII) was a Leap year starting on Saturday (link will display the full calendar of the Gregorian Calendar (or a Leap An image (from Latin imago) or picture is an artifact usually two-dimensional that has a similar appearance to some subject &mdashusually 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. 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 the stamp, and often constitutes the difference between a common and a rare stamp. Philately is the study and collecting of revenue and postage stamps 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. Embossing is the process of creating a three-dimensional image or design in Paper and other Ductile materials Switzerland (English pronunciation; Schweiz Swiss German: Schwyz or Schwiiz Suisse Svizzera Svizra officially the Swiss Confederation

See also

• Thomas Harry Saunders
• Dirty paper coding (DPC)
• Digital watermarking

External links

• How Watermarks are used

Watermarks in databases and other Watermark projects:

• http://www.ksbm.oeaw.ac.at/wz/wzma2.htm
• http://www.wm-portal.net/niki/index.php
• http://www.bernstein.oeaw.ac.at
• http://www.piccard-online.de

Bibliography on watermarks and papers in Greek manuscripts:

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