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Listening to Paper

Winter 2017
Winter 2017
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Timothy Barrett  is a professor in the University of Iowa Center for the Book and the School of Library and Information Science. His many years of research on early European handmade papers have been funded by the NEA, the Kress Foundation, the Institute for Museum and Library Services, and as of 2009, a MacArthur Fellowship. Barrett is author of two books, one website, seven videotapes, and thirty-six articles or book chapters on the history, technique, science, and aesthetics of hand papermaking. Someday in the future we will be able to talk to dolphins, whales, and chimpanzees, or at least we will learn a lot more than we know now about how and what they communicate to others of their own species. But to get to that level of understanding, first we have to learn to listen and decipher the meaning of the information being transmitted. In a similar sense, although paper can't actually talk, it does contain a lot of information about itself that we can learn to "hear" and that, in turn, can be interesting and even awe-inspiring to the paper historian, conservator, or artist. There is a wide range of paper tests, from high-tech, expensive, non-destructive procedures to inexpensive, low-tech methods that are available to better understand paper. I first realized the potential of paper analysis and testing in the late 70s when I discovered the William Barrow Laboratory's report on their analysis of 1,470 book papers made between 1507 and 1949.1 At the time I was beginning a quest to try to determine what characteristics of fifteenth-century European papers might explain their superior stability, strength, and integrity compared with papers made in subsequent centuries.

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In one of the plots in the report, Barrow documents a decline in pH from slightly alkaline early sheets to increasingly acidic papers made during subsequent dates. This research was pivotal in confirming the fact that long-lasting archival papers should have a neutral or slightly alkaline pH.2 Two things struck me about the Barrow research. First and foremost, Barrow got the paper to "talk" about the materials and methods used in its own making. This was a revelation to me. The scholarship to date had revealed little or nothing about early papermaking materials and techniques. But with his work, Barrow had opened up a magic portal for me—the papers themselves were effectively records of their own making. Secondly, I realized Barrow had not included the really interesting papers from the fifteenth century because all of his tests were destructive, executed on paper from broken (partial) or de-accessioned books. If I wanted to test papers from the fifteenth century, I would need to identify appropriate non-destructive testing methods, then replicate the Barrow Lab's work, but this time, include a wider range of early papers. A 2007 grant from the Institute of Museum and Library Services (IMLS) made this project possible. During our study we used two methods that required instruments that were expensive (around $40,000) but gave us valuable information. An Analytical Spectral Devices (ASD) near-infrared and visible light spectrometer allowed us to estimate gelatin content and paper color. In our research, we found that fifteenth-century papermakers were adding more gelatin to their paper compared with papermakers in subsequent centuries. We also noted that the earlier sheets were lighter in color, and thicker. A Bruker Tracer III X-ray florescence instrument gave us estimated parts per million values for calcium, iron, and other elements. The fifteenth-century sheets had more calcium and lower levels of iron compared with paper from later dates.3 Working with high-tech equipment can be highly informative, but what if you want to undertake research on paper characteristics and cannot afford the expensive instrumentation or the fees required to have your paper tested by a fully equipped lab? Here are some suggestions for a few tools and techniques that are destructive, but can be done with quite small paper samples. ph: A "colormetric" pH test pen can be used to help establish if a paper or raw material is alkaline or acidic.4 These pens take the form of a felt-tip marker filled with a pH-sensitive indicator solution instead of ink. A small dot made with one of these pens will turn purple if alkaline, yellow if acidic. This simple test is valuable, for example, to an artist who makes collage works with a wide range of handmade and machine-made papers. Note that the pen is of limited use on papers that are already colored, although they can be used on offwhite sheets or lightly tinted papers. lightfastness: The permanence of colorants is normally tested with a Fadeometer (or Fade-Ometer), another expensive piece of laboratory equipment. Inside, under controlled humidity and temperature conditions, a specimen of paper (or cloth, ink, or paint) is exposed to increasing hours of light from a very bright Xenon lamp. A low-cost approach consists of attaching a piece of colored paper to a similarly sized piece of mat board or card stock with thread or string ties.5 With scissors or a mat knife make 6 to 8 vertical cuts from the bottom up in the colored paper but leave enough uncut up at the top so that the strips will hang flat in place. Pull off one strip, mark it #1, and place it in a darkened storage area like a drawer. Put the assembly in a south-facing window, colored paper toward the bright light, leaning at an angle so that it does not get wet in the event the window collects condensation. Once a week pull off a strip, mark it with the next number, and place it in the dark storage area. When all but the last strip has been torn off, expose it for a final week, and then take the assembly down and line up all of the strips in order. If you have a very permanent color, you will notice minimal changes. If the color is fugitive, you will see substantial color loss from just one week of exposure to the light. The problem with this approach is that you cannot repeat the test and compare papers colored with different dyes or pigments because the weather and sunlight will not be identical from test to test. A more sophisticated approach would be to use a strong light of some kind, always keeping the test specimens the same distance from the lamp. Remember, a coloring agent that fades quickly is not necessarily bad, especially in artistic applications. Imagine an interactive process piece wherein visitors to a gallery are asked to choose from a selection of vegetable-dyed papers made by the artist. They are invited to apply objects, or write on Mylar and attach it to the surface of the paper and expose the combination to sunlight or a bright light source for a predetermined time. A quick-fading dye would produce a photogram-type image. The resulting pieces could be displayed on a dimly lit gallery wall or scanned into a composite artist book. In such a context, the impermanent coloring agent becomes an ideal tool in the artist's hands. sizing effectiveness: Sizing is a material added to a paper to change its resistance to the penetration of a liquid. Typical examples of surface sizes (applied to the paper after it is made) are gelatin or starch. Hercon 40 is a cellulose-reactive internal size that can be added to the pulp before sheet forming.6 There are industry-standard instruments and procedures for evaluating sizing effectiveness but they tend to be complicated and expensive. You can get a rough approximation of how well your paper is sized by putting a drop of water on the surface and watching to see how quickly it is absorbed. Little or no sizing and the drop will disappear immediately, lots of sizing and the drop will sit on top of the paper for a long time as if it was sitting on waxed paper. The same test can be used on papers made from the same fiber subjected to increased beating time; the more the fiber is beaten, the less absorbent the finished sheet. You can increase the reliability of your test by incorporating the following: (1) Use the same water and allow it to stabilize at room temperature; (2) Measure and adjust the temperature if needed so it is always the same; (3) Use an eye dropper to apply exactly one drop just above the surface; and (4) Time the period from drop to complete absorption with a stopwatch or timer. The last step will require setting your own standard for absorption such as "with oblique lighting from a desk lamp, full absorption occurs when water or a watery sheen is no longer visible at the surface of the sheet." For artists working with paper, remember that uneven or ineffective sizing is not necessarily a shortcoming. A surface size such as gelatin can be purposely applied locally with a brush in anticipation of using aqueous media later with a specific image in mind. When treated with watercolor later, for example, the color will spread into the sheet in the unsized areas, but stay much more on the surface of the sized areas.7 There are several non-destructive tests that can be used on paper to acquire data that may be useful to the papermaker, paper artist, or paper historian. These tests can identify qualities that send important signals about the skill of the papermaker, the quality of the raw material, the relative price of the paper, and thus, perhaps the intended audience of the written and printed message or image on the paper. Artists or contemporary hand papermakers can also use these parameters to classify papers in their collection to better understand how to use them in their creative pursuits. paper thickness: The fastest way for the early papermaker to make paper cheaper was to make it thinner. Conversely, thicker, more sumptuous paper cost more to produce. This can provide tell-tale information to the paper or book historian attempting to show that one edition of a book seems to have been aimed at a wealthier audience, while another was intended for customers less well off. For artists doing collage work, sorting their collected papers by thickness may facilitate more spontaneous art making later. A micrometer or dial-type thickness gauge is a useful tool for this purpose.8 Paper is often sold by grammage rather than thickness. The term GSM, or grams per square meter, refers to the number of grams a single sheet would weigh if it were one-meter square. This is a useful international system, more versatile than the old practice of selling various types of paper (i.e., book, art, bond) by pounds per ream of varying dimensions. With a gram scale and a metric ruler in centimeters, you will be able to calculate the GSM of even a small square or rectangle of paper.9 paper quality: Although judging quality is a subjective exercise and often depends on the expected use of the paper, we can evaluate a sheet by close examination. When held up against the light, a paper will reveal its formation quality and other indicators of skill in material selection and workmanship. Bits of straw or foreign material, lumps, folds, papermaker's tears, and "stretchmarks" are signs of quick or unskilled sheet forming or couching. At the other extreme are papers that have a minimum of stray fibers or debris, and in transmitted light show freedom from knots or clumps, and exhibit exceptional formation quality, evidence of careful couching, and a well-cared-for mould surface By using a range of testing methods, at both the high and low ends, we are beginning to appreciate more fully what paper has to say about itself. The future of non-destructive paper testing is especially ripe with exciting possibilities. The more closely we listen to paper, the more stories will be revealed to us, and the more we will learn about ourselves as a culture.  notes 1. William J. Barrow Research Laboratory, Permanence/Durability of the Book—VII: Physical and Chemical Properties of Book Papers, 1507–1949 (Richmond: W.J. Barrow Laboratory, 1974). 2. In addition to an alkaline pH, Barrow's specifications for making "permanent and durable" machine-made papers also required inclusion of an alkaline reserve such as 2% to 3% calcium carbonate, the use of high alpha cellulose fiber, and a neutral-pH internal sizing agent. 3. For details on our instrumentation, testing methods, and the overall goals and findings of the IMLS-funded project, visit the research report website at http://paper.lib.uiowa. edu/index.php or see a peer-reviewed publication at rest.2016.37.issue-2/res-2015-0017/res-2015-0017.xml (accessed July 11, 2017). 4. Abbey pH test pens are available online from a number of suppliers including Talas, Gaylord Archival, and Hollinger-Metal Edge. 5. Some colors may be sensitive to alkaline, buffered museum board, thus neutral-pH board is probably best. Common cardboard will suffice for preliminary experiments. 6. For comprehensive details on various sizing agents from the conservator's perspective see "Sizing/Resizing," in The Paper Conservation Catalog. 5th edition, compiled by Walter Henry (Washington, DC: The American Institute for Conservation, Book and Paper Group, 1988). Online at (accessed July 11, 2017). 7. For initial experiments with gelatin size, a 3.5% solution (3.5 grams in 100 milliliters of water) is recommended. Knox unflavored gelatin from the baking section of a grocery store will work. Warm the solution in a double boiler slowly until warm to the touch and the gelatin is dissolved. After a sizing session you can cool it, let it gel, store it in the refrigerator, and then use it again later by re-heating to return the gel to a warm solution. 8. A variety of micrometers and dial-type thickness gauges are available online from suppliers including MSC Industrial Supply Company and McMaster-Carr. 9. See Don Farnsworth's excellent smartphone or desktop calculator for doing this automatically at (accessed July 11, 2017). Additional details can be found on page 7 of Farnsworth's article at this link: 8de3/1498597220046/Determinate+Paper+June+27.pdf (accessed July 11, 2017)