Sometimes, forensic document examiners must determine whether pages have been added to a document or whether the document actually was created at a particular time. In either case, the examiner may resort to analyzing the paper.
Most paper is made of wood and cotton and often has chemical additives that affect its opacity, color, brightness, strength, and durability:
Coatings improve the appearance and surface properties of the paper and make the paper better for copiers, printers, or for writing.
Fillers add color, strength, and surface texture.
Sizings make the surface less porous to ink, so that writing and printing appear sharp and clear.
The types and amounts of each of these additives vary among manufacturers and paper types, and chemical testing can distinguish one type and manufacturer from another.
Another distinguishing characteristic of paper is its watermark, which is a translucent design on the paper that you can see by holding the page up to a light. This design indicates the manufacturer, the date of its production, and often for whom the paper was manufactured. Attempts to forge a watermark usually are easy to spot because true watermarks have fewer fibers than the rest of the page. Forged marks, however, actually are added images and thus have an underlying fiber density equal to the rest of the page.