Ownership Marking of Paper-Based Materials
Indelible identification marks have traditionally been placed on paper-based materials to help deter their theft and to establish ownership in the event of theft. Some institutions and collectors do not mark their holdings for a variety of reasons. For example, ownership marks cannot guarantee that an item, or portions of it, will not be stolen. Second, the presence of a mark on an item does not necessarily prove ownership or provenance, since determined thieves can find ways to forge or alter ownership marks. In addition, marking methods may alter an item in a manner that changes its market value - an issue of particular importance to collectors. Curators in institutions are often less concerned about a change in the market value of their holdings because the consider them to be in their permanent home.
Paper-based materials may be indelibly marked with an identifying symbol by embossing, by punching or perforating, or by stamping with ink. Alternative methods of marking library materials are being employed and the Library of Congress will report on them when appropriate research has been conducted.
Embossed Ownership Marks
Embossing is a process in which symbols or words are represented in relief. A piece of paper is embossed by inserting it between two opposing male and female dies mounted on a hand-held device. The device in squeezed to press the two dies together, which ruptures the fibers of the paper and creates the relief image. On most papers, embossed symbols can be smoothed out to become nearly invisible. Unless scrutinized closely under good raking light, smoothed out embossing can be easily missed during inspection.
Punched and Perforated Ownership Marks
Like the embossing tool, punches and perforators also consist of opposing male and female dies. Unlike embossing, however, punching and perforating actually remove small bits of paper from the item. In general, a punch creates an image (for example letters or numbers) by removing a single piece of paper. A perforator removes numerous smaller pieces of paper, usually in the shape of small discs. Viewed together, these small, round holes form letters, words or other distinctive images. Although inexpensive methods of marking, both punching and perforating damage and disfigure materials. Of the two, punched marks are less desirable because they are more obtrusive and more susceptible to tearing in the process of handling.
Stamped-Ink Ownership Marks
Invisible Inks
Invisible inks, while commercially available, have been known to lose their invisibility over time and therefore should not be considered permanent. Invisible inks are ineffective as psychological deterrents to theft. Also, since marks made with invisible ink are only visible under ultraviolet light, the ink is only useful in identifying a stolen document after it has been recovered. Even though invisible ink has the advantage of not defacing documents, it should be not be considered suitable for ownership identification under these circumstances.
Visible Inks
Stamping with visible ink is one of the oldest methods of marking the ownership of paper-based materials. The mark is made by using a lightly-inked, hand-held stamp to transfer an image to the paper. This technique has been used for centuries, particularly in China and Japan. In fact, Oriental scrolls, silk paintings, and wood block prints often carry several ownership stamps, indicating a long line of previous owners. Stamping with visible ink is still a common practice, and is, in fact, the most commonly used method of ownership marking worldwide.
The ideal ink for marking paper-based materials should have all of the following properties: It should be non-fading (i.e., stable for at lest one hundred years as measured by accelerated aging and light exposure tests) and not removeable with solvents or bleaches. It should be nondestructive to paper and should neither bleed nor migrate into surrounding or adjacent paper. It should have a neutral or slightly alkaline pH (pH 7.0-8.0). Finally, it should be slow to dry on the stamp pad but fast to dry on the document.
Stamps and Stamp Pads
Ownership marks should be applied with stamps made of high quality, sharply cut rubber or plastic. To reduce the risk of making an overly inked impression, the image design should consist only of thin lines. The image should be as small as possible, but not so small that it compromises the mark's identification value.
Although foam rubber or felt stamp pads may be used, a balsa wood pad is recommended because it helps prevent over-inking while still providing a uniform image. Balsa pads are available from several archival suppliers and can be specially ordered at some stationary stores. They can also be made easily by cutting (across the grain) a ½" thick layer of wood from a balsa block that is somewhat larger than the stamp (1 X 2 and 2 X 3 inches are common sizes). The end grain of the ½" thick layer should be used as the stamping surface. It can be sanded smooth with fine-grain sand paper for better inking and stamping.
Library of Congress Manuscript Marking Ink
In the past, inks that met the above specifications were not available commercially. In consequence, inks that meet the specified requirements were formulated and tested by the Library in cooperation with the United States Government Printing Office. In the interests of security, the Library of Congress and the Printing Office agreed not to publish the formulas for these inks because such information might make it possible to develop a means for their removal.
The Library of Congress manuscript marking ink is available to the public in two colors: blue and black. Exhaustive testing has proven them to be resistant to the strongest bleaches and solvents. They have a pH of 7 - 7.5 and should not harm the paper chemically. Both colors are non-bleeding and non-migrating on almost all papers when properly applied. They may bleed slightly on onion skin paper or on exceptionally thin and porous papers. Also, the inks do not lend themselves well to use on highly calendared paper or coated papers.
The inks are highly resistant to fading and have been demonstrated to withstand 160 days of exposure in a standard Fadeometer (equivalent to 100 years of exposure to normal sunlight). After the equivalent of 200 years of artificial aging in both humid and dry ovens, no ink-related deterioration of the paper has been observed.
Method of Application
Library of Congress manuscript marking inks are formulated to be applied with a stamp that has been inked with a balsa stamp pad. The best way to apply the ink to the pad is with a plastic or wooden stick that is approximately 1/8" in diameter. Dip the stick into the ink. Allow excess ink to drip from the end of the stick back into the bottle. Roll the stick across the pad to distribute the ink evenly. The edges of the pad do not require inking. Ink area of pad only slightly larger than the stamp. Allow the inked pad to stand for 30-60 minutes before using in order to permit migration of the ink into he pad. Practice using stamp on scrap paper before marking original.
New balsa wood pads may require more frequent re-inking during stamping until the wood block is thoroughly saturated, or "primed." Once primed, the inked pad can be refreshed by applying to it one drop of water one week and one drop of ink the next week or as needed. The water can be applied by a medicine dropper. Use the ink stick to distribute the water over the surface of the pad.
The problem most frequently observed in the use of the ink is that an excessive amount of it has been applied to the pad. If the pad is overly inked, the stamp can pick up to much ink. As a result, bleeding or strike-through can occur, particularly on thin or tissue papers. If one is uncertain about whether the pad is over-inked, the prudent approach would be to test the stamp on scrap paper before using it on original materials. If over-inking has inadvertently occurred, the test stamping will remove it.
When stamping original materials (manuscripts, maps, works or art, photographs, and books), take care to strike the paper squarely in order to make a clear sharp, uniformly inked impression. Work on a lat, smooth surface to ensure that library materials no not become creased or broken during marking. Because the ink will dry at different rates when used on different types of papers, ensure that the mark is dry before stacking single sheet items or closing a stamped book. This will prevent offprinting of the mark onto adjacent materials; if this occurs the image will be permanently defaced.
Placement of Marks
The exact placement of ownership marks on paper-based materials is governed by preference, established practice, and common sense. At the Library of Congress, for example, ownership marks are placed where they are easy to locate and readily visible - in the same place on the same page of every book, for example. To facilitate identification, materials should be marked consistently in the same general location. Ideally, an ownership mark should neither deface an item nor obliterate any part of its image or text. Single sheets that are blank on one side should be marked on the blank side, if feasible. Preferably, the library materials should be stamped on the verso of the sheet. Do not stamp items in highlight areas (white) because the ink may show through onto the image side. If the item has a white border around the image, stamp the back of the item in the border area. Then, if bleed through should happen to occur, it will be in a non-image area. However, it needs to be remembered that border areas can easily be cut from an item, thus removing the mark.
Stamping Ownership Marks on Photographs
Most fiber-based photographs, except plastic or resin-coated, can be stamped with the Library of Congress manuscript marking inks. The above criteria for application and placement of marks should be followed.
Availability of the Inks
The Library of Congress manuscript marking ink is available, free of charge, to library, archive or museum institutions. Please send your name, institution affliation and address to Ask A Librarian.