Watermarks—designs impressed into paper in the manufacturing process—result from wires twisted into shapes and sewn onto the mold used to make the paper. They provide the basis for identification of batches of paper stock in much the same way that fingerprints and, increasingly, DNA evidence and retinal scans do for human beings. Although the original purpose for their use is unclear, they came to be used by paper manufacturers as a kind of trademark for them and their mills. The designs are highly variable and often whimsical: unicorns, dogs, mermaids, letters, numbers, flowers, bells, circles, keys, armorials, for example. Watermarks are so useful for authenticating paper that the U.S. Treasury Department incorporates them with a chemical process in the production of the new $100, $50, and $20 bills.

The study of watermarks and the recovery of knowledge concerning the processes of paper manufacture (papers produced by hand rather than machine) have produced important results in several fields in the last three decades. In 1967, Allan Stevenson established that the Missale Speciale, once thought to have been printed by Gutenberg and to represent one of the earliest products of moveable type, must instead, on the evidence of its paper stocks, have been printed in the 1470s, more than thirty years later than once thought. Paul Needham, again relying almost entirely on the evidence of paper stocks, has revised the date of the printing of the first edition of the Canterbury Tales (Caxton) to late 1476/early 1477, making it the very earliest book printed in English in England.

At present, watermarks are providing the critical evidence in two extremely important problems in modern scholarship: the authorship of a long theological treatise, De Doctrina Christiana, long thought to be the work of John Milton, and the status and date of a great many documents presently attributed to Thomas Jefferson. For three centuries, scholars have used theDe Doctrina as the main basis for interpreting Milton’s works (particularly Paradise Lost); however, just in 1996 it was discovered that Milton’s name was inscribed on the manuscript by someone other than Milton. The watermarks in the paper of the manuscript may make it possible to date the manuscript. Scholars have argued that the manuscript is not in Milton’s hand because it was written after his blindness in 1652. However, if the watermarks significantly predate 1652, then the fact that the manuscript is not in Milton’s hand weighs against his authorship. Further, the watermarks in the paper used for the De Doctrina do not appear in other paper stocks used by Milton. Sullivan, who first detected the De Doctrina watermarks, presented a paper on this problem at the 2001 Modern Language Association Conference.

Thomas L. Gravell has determined, through the evidence of the watermarks, that a number of "Jefferson" letters, obviously copied by scriveners but signed by Jefferson, are in fact written on paper manufactured some years after the dates on the letters: they turn out to be copies of letters Jefferson sent, made by the recipients for Jefferson, and thus may not accurately represent Jefferson’s originals. Obviously, much work remains on both problems, but there is no doubt that watermark evidence will play an important role in any solutions. The Gravell Collection includes 876 watermarks from the Thomas Jefferson, General Correspondence collection at the Library of Congress.

Additional examples of the usefulness and significance of watermark evidence abound. A letter from Benjamin Franklin at the Folger Shakespeare Library, apparently written to Captain Timothy Folger, and in Franklin’s hand throughout, turns out on examination of the watermark evidence and structural features of the paper to be constructed from at least two different documents (see Yeandle 2000).

Peter Bower has used watermarks and other forensic paper evidence to dispute the authenticity of $1.2 billion worth of U.S. Treasury Bonds issued by the War Department in the 1940s which, if validated (they really do exist, issued as part of a cloak-and-dagger scheme during World War II) would, with accrued interest, bankrupt the U.S. Treasury (Bower 2001).

Watermarks are also an important component in cataloging, dating, and authenticating prints by Rembrandt in the National Gallery of Art's Rembrandt Project (Ash and Fletcher 1998; Ash and Fletcher 2000) and in the classification of the "lifetime" and "posthumous" lithographs of Whistler. In the field of musicology, watermarks have provided the evidence for the establishment of a reliable chronology of the Dresden manuscript sources for Telemann's Sonatas (Zohn 2000) as well as for the reconstruction of the original 1788 version of Mozart's Don Giovanni. Watermarks and paper study have been instrumental in redating works by Beethoven and Handel (Konrad 2000).

The date of a stock of paper, produced from a pair of molds, can be constrained to a very narrow span of time, as the molds, and especially the watermarks attached to them, deteriorate rapidly. While some remnant sheets might survive unused for a lengthy period of time, the bulk of that run of paper will be consumed fairly quickly, especially by printers (as compared with scribes) who could not afford to warehouse a large inventory of paper and whose technology consumed large quantities of paper as a matter of course. Thus, while the discovery of a watermark very similar to one which a scholar, book-seller, or archivist might be trying to date will be generally helpful, the discovery of a dated, identical mark will be analogous to the matching of two strings of DNA. Many undated books, manuscripts, and letters could be dated quite precisely on such grounds if the means for doing so were made more widely available (see, e.g., (Mosser 2007). The data and images in the Thomas L. Gravell Watermark Archive makes this possible for a world-wide audience. Accompanying each image with a metric rule allows for precise, scientific matching of watermarks with those in the collection. Watermarks can provide more precise means for dating a document or artifact than even a declaration of date by the printer, artist, or author. For example, William Caxton’s declarations of printing dates have proven to be unreliable; William Shakespeare’s second edition of A Midsummer Night’s Dream bears a date of 1619, even though the actual date of its printing was 1600; and lithographs by Rembrandt and Whistler are known to have been pulled posthumously.

By making available a wide range of dated watermarks found in American and European paper stocks (dating from the thirteenth through the early nineteenth century), the Thomas L. Gravell Watermark Archive database provides scholars who work in areas involving paper evidence with an invaluable, powerful, readily accessible, and free resource for authenticating and dating paper artifacts as well as for locating other kinds of watermark evidence. The only other means of accessing data and images the Archive provides would be by visiting each of the institutions and examining the tens of thousands of artifacts from which Gravell, Briquet, and others have derived their collections. For the institutions from which the data is derived, the Gravell Archive adds an extra dimension of value to their holdings by making information on the watermarks found in their documents freely available, in a searchable database, from anywhere in the world. This in turn adds a layer of protection for these collections by obviating the need for numerous researchers to verify the same information over and over again, an activity that would require the handling of precious, fragile materials.