But, What Is It? How Research Science Informs Preservation

I’m a research scientist and I’ve worked in a laser, microscopy, or spectroscopy laboratory (and sometimes a lovely combination of the three) for the past seventeen years. The last five of those years I’ve been lucky to call myself a Chemist at the Library of Congress, working in the optical properties lab of the Preservation Research and Testing Division. Now you may be asking yourself (and you certainly aren’t alone in wondering) just what exactly is a chemist doing in a library? You may be surprised to learn that scientists are working away behind the scenes in many museums and institutions that house our cultural heritage, but I want to share my favorite, material research and identification.

Preservation typically begins with a question, in my head I call it “but, what is it?” Sounds silly, but it’s a really important question. Cultural heritage objects can be down-right finicky. Some materials are sensitive to light and others aren’t, some pigments are stable in a water wash, while others could get washed away, and still some other colors won’t mind so long as the pH is just right. And don’t get me started on how the temperature and humidity need to be just so. It’s a bit like Goldilocks. This is why there is a dedicated team of scientists right in the Library, because we can answer “but, what is it?” and conservators can make their treatments just right.

Fiber optic reflectance spectroscopy analysis on a Japanese woodblock print.

Fiber optic reflectance spectroscopy being performed on the faded Japanese print. This instrument shines light in the ultraviolet, visible, and infrared wavelength range onto the object and captures whatever light is reflected back. Light that is not reflected back has been absorbed by the material, leading to a pattern of peaks and valleys that are material specific. Photo by Tana Villafana.

One of my first long term research projects at the Library was with my friend and colleague, paper conservator Gwenanne Edwards. She wanted to know why, of these two similar impressions of a Japanese woodblock prints, one was faded and one was not. Understanding the material aspects of the prints were crucial for developing a proper treatment; in other words, Gwenanne needed to know what caused the fading in order to properly protect and preserve the prints. Did the two prints have the same colorant palette, meaning the fading came from previous exposure to different environments and materials, or did the prints have two different sets of palettes with the faded print having colorants more susceptible to the environment? The only way to find out was to identify the colorants on both prints and we used a bit of the, what I enjoy calling, “and the kitchen sink” method.

We examined all the different colors on the prints using x-ray fluorescence spectroscopy, Raman spectroscopy, fiber optic reflectance spectroscopy, microscopy, fluorescence microscopy, and multi-modal and multi-spectral imaging. (Special note, these methods are all non-invasive and non-contact, i.e., no prints were harmed in the making of this study.) Then we went further, ordering natural materials from Japan to extract, create, and print our own colorants so that we could have reference materials for comparison. Comparing spectra of known Japanese print colorants to the two prints was a crucial step, particularly for mixtures and even more so for the faded print.

Portable Raman spectroscopy analysis on a Japanese woodblock print.

Raman spectroscopy being performed on the non- faded Japanese print. This instrument uses infrared laser emission, shining onto the area of interest and collecting the light scattered back. In Raman spectroscopy, the wavelength of the scattered light corresponds to the energy of a vibration in a chemical bond, which is very specific and used for material identification. Photo by Tana Villafana.

Using our reference colorants, we created over 1,000 samples and went back to the kitchen sink to collect the same set of data we had on the two prints. In the end, we made two important discoveries: first, the colorant palettes on the two prints were the same, and second, the non-faded print was coated with an iron-rich crystalline wax. Gwenanne now knew the identity of each colorant and therefore, how to properly treat and store the prints to prevent any further degradation. She also knew to keep any heat related treatments far away from the wax coated print (heat and wax are a bad combination). During the course of the study, we developed a protocol for studying Japanese woodblock prints and a reference collection of historic Japanese materials, not only the materials but their spectroscopic characterizations as well. This is important for any future work on Japanese prints and, with the Prints and Photographs Division of the Library of Congress containing over 2,500 Japanese woodblock prints and drawings, I imagine there will be future work.

A scientist and a conservator creating Japanese print colorants from natural materials.

Photos of Tana and Gwenanne during their creation of reference Japanese woodblock colorants and samples.

Our work together extended beyond the Library, as well. We produced two published manuscripts from this study: one details exactly how we made these reference materials (available to any who needs to duplicate such colorants), and the other explains all the material aspects of the two prints and the protocol of our study. Now any researcher, conservator, or anyone with an interest in Japanese prints can use this information to aid in their material research or treatment plans. Interestingly, we have had not found any other print with a wax coating or a scholar who can speak to its presence. Whether the coating was intentionally added at the beginning of the print’s life or at a different date is still a mystery, however we know now that the coating protected the colorants from water damage and fading due to ultraviolet light.

This is just one of many wonderful research projects I’ve been a part of at the Library and highlights the incredible science going on behind the scenes, showing how material science directly affects the collections and their preservation. Now you know why scientists can occasionally be found lurking in unexpected places, like the sub-basement of the Library of Congress.