Watermark

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Watermark

A watermark is a recognizable image or pattern in paper that appears as various shades of lightness or 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. Watermarks have been used on postage stamps, currency, and other government documents to discourage counterfeiting. There are two main types of watermarks: digital watermarks and physical watermarks.

History

The origin of watermarks dates back to the 13th century in Italy. The first watermarks were used in the Fabriano paper mills. These early watermarks were simple designs, often the manufacturer's logo or a symbol representing the paper mill. Over time, the complexity and variety of watermarks increased, and they became a standard feature in high-quality paper production.

Types of Watermarks

Physical Watermarks

Physical watermarks are created during the paper manufacturing process. They are typically made by impressing a water-coated metal stamp or dandy roll onto the paper during production. This process creates a variation in the paper's thickness, which becomes visible when the paper is held up to the light. Physical watermarks are commonly used in currency, passports, and other important documents to prevent counterfeiting.

Digital Watermarks

Digital watermarks are used in digital media to protect intellectual property. They are embedded into digital files such as images, audio, and video. Digital watermarks can be visible or invisible and are used to verify the authenticity of the content or to track the distribution of the media. They are an important tool in digital rights management (DRM).

Applications

Watermarks have a wide range of applications, including:

• Currency: To prevent counterfeiting, most modern banknotes include watermarks.
• Postage stamps: Watermarks are used to prevent the production of counterfeit stamps.
• Passports and identification documents: Watermarks help to verify the authenticity of these documents.
• Digital media: Watermarks protect intellectual property and help track the distribution of digital content.

Detection and Analysis

The detection and analysis of watermarks can be performed using various methods. For physical watermarks, the most common method is to hold the paper up to the light. For digital watermarks, specialized software is used to detect and analyze the embedded information.

See Also

• Counterfeiting
• Digital rights management
• Currency
• Postage stamp
• Paper