From PittconReviewed by Danielle Ellis, B.Sc.Sep 2 2025
Eric Monroe shares insights into his role as Head of the Scientific Laboratory Section within the Preservation Research and Testing Division, discussing the work involved and its impact on preservation efforts.
Can you tell our readers about the journey to your current role in the Library of Congress?
I started out at a small liberal arts college, thinking I wanted to be a journalist. As part of the curriculum, I had to take a physical science course, so I enrolled in chemistry during my freshman year. That class completely changed my trajectory—I fell in love with the subject. Research turned out to be far more engaging and intellectually stimulating than my journalism courses, and by the time I was between my junior and senior years, I’d decided to pursue graduate school.
Since then, I’ve worked in analytical neuroscience, contributing to the early development of multi-mass spectrometry imaging techniques for tissue analysis. My experience has also included research in HIV and electrochemistry. For a while, I thought I wanted to become a professor, but that path didn’t materialize the way I expected. Instead, I took a role overseeing the chemical characterization lab at a textiles company that specialized in floor coverings. Ultimately, I realized that working in industry wasn’t the right fit for me.
When it came time to move to the DC area—partly to solve a two-body problem and partly in search of a new chapter—I began exploring opportunities. While browsing usajobs.gov, I came across a scientist position at the Library of Congress. It caught my attention, I applied, and fortunately, they brought me on board.
Two years later, I was promoted into a supervisory role, and the rest is history. It’s been an incredible journey. The work is fascinating, genuinely engaging, and far more enjoyable than I ever expected.
Can you tell our readers about the Library of Congress itself, the collections it has, and your role within the library?
The Library of Congress, established in 1800, is the largest library in the world. It was originally created to serve as the library for the US Congress and, up until around 1900, was actually housed in the US Capitol building.
After several fires over the years, the library relocated to a dedicated building across the street. Today, we have three buildings on Capitol Hill, along with two offsite storage facilities.
While books are certainly part of our holdings, they aren’t our largest collection. The library houses a vast and diverse range of materials. For instance, we maintain a substantial manuscript collection, including most of the early presidential papers. We also hold the world’s largest collection of glass flutes as part of our extensive musical instrument archive. Our audiovisual materials, which are stored in Culpeper, Virginia, represent another major collection. We have large holdings of maps, globes, and even a significant collection of pre-Columbian art and artifacts.
As scientists at the Library of Congress, our work often centers on assessing the physical condition of materials. We help answer questions such as: Is this item degrading? What conservation methods might be appropriate? In these cases, we collaborate closely with our conservators to determine the best course of action.
Researchers utilize our collections, in collaboration with our curatorial staff. My group offers our scientific services to help address questions that researchers, curatorial staff, or conservators may have regarding collections. That may be questions of how items were produced, what the state of preservation/degradation may be, or to aid in the interpretation of the collection object.
Image Credit: KinoMasterskaya/Shutterstock.com
Our goal is to adapt to the needs of each visiting researcher. We have a diverse team of around 15 people, each with different expertise and cross-training. That flexibility allows us to address a wide range of questions—whether it’s identifying the composition of a material, advising on conservation, or supporting historical analysis. And if we don’t know the exact answer, we’re usually able to get very close.
What sort of analytical techniques do you employ in your department, and how important is flexibility when working with researchers and curators from different fields?
This is by far the most well-equipped lab I’ve ever worked in. At the Library of Congress, we operate two main laboratories.
Our wet analytical lab (shown below) focuses on techniques such as HPLC, SEC, mass spectrometry, microscopy, and pH testing. Much of this work supports our quality assurance testing program or involves analyzing simulated materials. Many of our long-term research projects center on understanding how materials degrade over time.
Our imaging, microscopy, and spectroscopy lab includes a wide array of tools: a multispectral imaging system, Raman spectroscopy, a custom non-contact audio playback system known as IRENE, X-ray fluorescence, FTIR, fiber optic reflectance spectroscopy, high-resolution microscopy, X-ray diffraction, and electron microscopy with EDS capabilities.
In some cases, we have multiple versions of the same instrument. That’s largely because many of today’s analytical tools are portable or miniaturized, allowing us to bring the equipment directly to the collections. That’s especially important when dealing with items that are large, extremely fragile, or too valuable to move. Our collections are far more than just paper documents—they include large volumes, complex objects, and intricate pre-Columbian artifacts that require close examination in hard-to-reach areas.
Image Credit: The Library of Congress
When objects do come into the lab, it's common for curators or researchers to join us during the analysis. These hands-on collaborations often lead to rich, interdisciplinary exchanges.
We often describe our work as transdisciplinary. A single project might involve a scientist like myself, a medieval historian, and an educator—all approaching the material from different angles. Some projects are straightforward and can be wrapped up in a couple of hours. Others evolve into multi-year studies that reveal layers of insight over time.
You mentioned GC-MS as one of the analytical tools in your lab. How have you adapted and transferred these technologies for use at the Library of Congress?
Some of the instruments we use in our labs are standard, commercially available tools—but in most cases, we adapt or refine how we use them. That might involve adjusting how we collect and analyze data, modifying the sampling setup, rethinking how samples are mounted, or even deciding not to sample at all.
This flexibility is essential because, when working with collection items, taking a sample often isn’t an option. Many materials are too valuable, too fragile, or simply irreplaceable. On top of that, degrading items can release volatile organic compounds (VOCs), which pose additional risks. About a decade ago—before I joined the Library—sampling of VOCs was done using contact or non-contact solid-phase microextraction (SPME).
Today, we have a comprehensive quality assurance materials testing program in place. Any material that might be used near our collections—whether it’s for a new storage vault, exhibition case, or construction in a collection space—must first be tested. The goal is to reduce potential risks to the objects from materials that will be in close proximity for extended periods.
This kind of testing is relevant across the entire cultural heritage sector. In the 1970s, W.A. Oddy developed what’s now known as the Oddy test after discovering that a newly installed storage case had damaged some of his coins. It’s been a widely used standard ever since.
The Oddy test involves placing a few grams of the material in a beaker with three metal coupons—copper, silver, and lead—under high humidity at 60°C for 28 days. The idea is that if the material is safe, the metal coupons will come out unchanged—no corrosion, discoloration, or residue.
But I found this process too slow, especially considering how tight construction timelines often are. When I worked in the textiles industry, I was involved in a development project focused on foams used in automotive interiors. That’s where I first encountered the VDA 278 test—a faster, direct thermal desorption method.
VDA 278 involves placing a small sample (just a few milligrams) into a sealed vial and heating it to 90°C for 30 minutes. Any compounds released are collected in a cold inlet on a gas chromatograph, then analyzed. Because it’s a closed system, we can see not only what’s coming off the sample, but how much.
We've been using this method at the Library for almost eight years now, and it’s given us a solid understanding of how results from VDA 278 correlate with those from the Oddy test.
In some cases, we already know which compounds are problematic. For instance, a particular heat stabilization additive in certain PVC boards—often used for exhibition cases—will tarnish silver in just a few months. Now, we can screen for that compound in two hours rather than waiting nearly a month for Oddy results.
We also use this approach for air sampling. Air can be drawn either directly onto a sorbent tube or captured in a sampling bag, then passed through a thermal desorption system in the lab. This gives us insights into the air quality around our collections and exhibitions.
For example, we might sample the air inside an exhibit case just before placing objects inside to make sure nothing harmful has emerged during construction. Or, if someone notices an unusual odor near a collection, we can analyze the air to identify VOCs that may signal degradation. These chemical markers can tell us whether an object needs to be rehoused, isolated, or stabilized through conservation.
We understand that a colleague of yours introduced the same methodology at a similar time in another institution. How did their work impact yours, and vice versa?
The introduction of direct thermal desorption to the cultural heritage field came from two directions at once. I brought it with me from my background in industry, while around the same time, Mike Samide at Butler University and Greg Smith at the Indianapolis Museum of Art began adapting their pyrolysis unit—essentially turning down the temperature to apply a similar methodology.
Interestingly, I studied at Butler, and Dr. Samide was one of my analytical chemistry professors. Back then, neither of us was aware that cultural heritage science even existed as a field. Later, Mike did a sabbatical with Greg to help address issues the museum was having with its encasements, which led them into this area of work.
Since then, direct thermal desorption has been widely adopted—especially by larger cultural heritage institutions—as a valuable tool for studying VOCs and interpreting Oddy test results with greater nuance.
Through collaboration with the American Institute for Conservation’s Materials Working Group, we've participated in several round-robin studies. In these, labs around the world analyze the same samples, often with slight variations in methodology. This kind of collective testing has been incredibly useful.
One key difference lies in our instrument inlets. For instance, my system is set up to run at lower temperatures over longer periods, which allows us to trap more volatiles. Other setups might run at higher temperatures—say, 90°C, 120°C, or 150°C—for much shorter durations, from just a few minutes up to half an hour. What we've found is that we’re qualitatively detecting the same compounds across labs but in different ratios.
My configuration tends to be more sensitive simply because it gives more time for volatile compounds to accumulate. If the goal is just to confirm whether a compound is present, this setup provides a faster, more reliable screening mechanism.
As scientists, we like to understand the full picture. So it's been valuable to build an internal database—and to share data across the conservation science community—on problematic compounds. Whether they're actively causing damage or presenting elevated risks, identifying and tracking these substances allows us to better mitigate threats to collections.
The Library of Congress holds important historical documents that were integral to the establishment of the United States as we know it today, including the early drafts of the Declaration of Independence. Could you tell us about the incredible findings and the work done on those documents using spectral imaging techniques?
One of the true treasures at the Library of Congress is Thomas Jefferson’s handwritten draft of the Declaration of Independence.
What makes this document particularly fascinating is how it serves as an early example of “track changes.” Jefferson often crossed out words and neatly wrote the revisions above. In some instances, he even annotated the margins to credit suggestions to others—Mr. Adams or Dr. Franklin, for example.
But partway through the second page, there's a revision that stands out from the rest. It's a passage referring to the king's role in inciting “treasonable insurrections against our fellow citizens” and mentions the forfeiture of property. These lines never made it into the final version of the Declaration. Notably, under the word “citizens,” there’s a visible smudge—something not seen elsewhere in the document—suggesting this edit was handled differently.
Revealing Hidden Histories with Spectroscopy & Imaging | Pittcon Thought Leader: Eric Monroe
To better understand what was originally written, we used multispectral imaging—a technique that allows us to study materials by illuminating them with small, controlled bands of light, ranging from ultraviolet to near-infrared. The system uses LED lights and a high-resolution black-and-white camera to capture subtle variations as different inks or materials respond to different wavelengths.
The result is a kind of data cube, where details fade in and out as you move through the image stack. By analyzing these wavebands, we were able to isolate and enhance what lay beneath the smudge under “citizens.” With some computational processing, the original phrase was revealed: “our fellow subjects.” That one word dramatically shifts the tone and intent of the sentence.
A historian later discovered a relevant clue. Jefferson had recently been working on the Virginia State Constitution, released just weeks before. That document uses very similar language, including the phrase “treasonable insurrections against our fellow subjects.” It appears Jefferson initially borrowed this phrasing but realized it wasn’t fitting for a nation seeking independence. He removed it, smudged the ink, and carefully rewrote the section to reflect a new national identity. That version—“citizens”—endured.
This project is a great example of how our lab’s tools, particularly multispectral imaging, can reveal hidden layers of history. These techniques help us recover redacted or faded text, offering insights into the drafting process and the creator’s thought patterns. In some cases, what we uncover can shift how a document is interpreted entirely.
In this case, because the ink across the edits appears consistent, we know the changes were made in real time—smudged, adjusted, and neatly corrected as Jefferson wrote.
Was the fact that it was the same ink challenging?
Yes, the fact that it was the same ink did make things more challenging. It lessened the guarantee of success. For example, a very old document written in iron gall ink and later overwritten with a black Sharpie is much easier to work with because the inks are completely different and respond very differently under various conditions.
But I’ve been amazed at what’s been achieved in this area, thanks to advancements in computational tools and the increase in the number of wavebands we’re now able to collect.
What was the subject of your talk at Pittcon?
My talk was on a 16th-century prayer book called The Veil of Veronica—a large, well-worn book with numerous paste-downs, including one that had been removed for later use, which was common in that period.
We were specifically looking at an image of Jesus from the Veil of Veronica story, where the pigment used is black. The image shows Jesus on his way to be crucified, and Veronica wipes the sweat from his face, transferring it to a veil—one of the holy relics.
I understand that this prayer book was owned by nuns in Northern Germany.
This small prayer book was written in two hands, entirely in iron gall ink, suggesting it was created by two nuns as a working document. It’s still in its original binding, and the cover is well-worn from use, indicating it played an active role in spiritual life within a 16th-century Northern German convent.
As the prayers progress through the book, several images are pasted in—often square and partially colored. At least one appears to have been removed and reused, a practice typical for the time. The interior leaflet of the cover is made from a different, seemingly unrelated piece of parchment—also not unusual for the period.
The book features many paste-ins, including one that drew particular interest from the curator. When the item came into the Library about 70 years ago, the cataloger noted that it was “unfortunate what happened to this paste-in,” suggesting the artist had chosen the wrong palette and that Jesus’ blackened face was the result of degradation.
Image Credit: The Library of Congress
The curator—a medieval historian—asked us to determine whether this was a conservation issue or if something else was going on. We found that the cataloger had been mistaken.
We began with multispectral imaging, which can be tricky with black inks but revealed several types of black inks used on the page. The handwriting was done in iron gall ink, which also appeared on the small pasted-in medallion showing Jesus’ face. The border used iron gall, the hair appeared to be iron gall as well, but the face and the nimbus were rendered in different black inks.
These differences helped us identify key areas to target with additional non-contact spectroscopic techniques.
Under magnification, we saw two distinct grays used on the face. The hair appeared as a simple black line, likely iron gall ink, with no visible shine. The face, by contrast, had a slightly grayer tone and a shimmer. The nimbus was also gray and slightly shiny.
Next, we used fiber optic reflectance spectroscopy, which examines material responses from the UV through the near IR. While typically used to study organics, it provided a useful signal for the iron gall ink in the main text, the hair, and the face.
That signal was initially very flat. But after increasing the intensity tenfold, we could see that the line around the hair resembled iron gall ink, although something else seemed to be suppressing the signal. The face’s signal remained nearly flat, consistent with carbon black—but we determined it wasn’t carbon black.
We then turned to micro-XRF, using a 100- or 200-micron spot size to focus on very small features—especially important when analyzing ink lines or small details. We targeted seven specific areas and collected multiple spectra from each.
The results showed multiple types of iron gall ink, each with different vitriols. The hair matched iron gall ink, but the face was entirely different, containing silica and titanium—neither of which makes sense as a pigment, nor would they discolor over time. These components were found across several areas of the face, strongly suggesting intentional use.
The nimbus was something else entirely. It showed silver and sulfur atop a dense ground, indicating it had likely been silver leaf that had since tarnished.
Using XRF mapping, we created visual representations of material distribution across the medallion—valuable for curators and researchers. The hair area confirmed the presence of iron gall ink, with added lead. This indicated either a mixture of iron gall ink and lead or a layer of lead beneath. Lead can suppress signals, which aligned with our observations.
We also identified aluminum and sulfur in the red around the halo, pointing to a Brazilwood lake pigment—consistent with what we saw in force microscopy. Mercury was found in the lips, and azurite was detected in a blue mark on the nose and surrounding area. These features seemed intentional, though their meaning wasn’t immediately clear.
We returned to the volume with the curator and researcher using portable microscopes. We discovered that the facing page had picked up particles that had flaked off the medallion, along with a larger area where the pigment was lifting.
We sampled the transferred particles. X-ray diffraction ruled out known titanium-bearing minerals. Using Raman spectroscopy, we identified quartz, calcite, and carbon. It still wasn’t clear why this blend was used as a pigment, but we had solid chemical data.
To better understand the context, we consulted with curators and historians. A reference to pilgrim’s badges shed light on the mystery.
The Veil of Veronica is one of the holy relics held at the Vatican and was a major pilgrimage destination in the 16th century. We now believe the face was rendered in black to emulate pewter pilgrim badges.
This prayer book, created by cloistered nuns in 16th-century Northern Germany, wasn’t just a rote copy of standard prayers. The nuns would not have had the opportunity to travel to Rome. Instead, it’s possible that the book was used in a spiritual exercise—where a nun removed herself from daily life for the time it would take to make the pilgrimage in spirit.
What we may be seeing is a nun’s meditative process as she undertook a spiritual journey. Upon completion, a senior nun could have distributed these “badges” to mark the occasion—essentially inserting them into what was, in effect, her spiritual scrapbook.
These findings shift our understanding of the book. It’s no longer just a historical artifact—it’s a living, breathing document of a personal spiritual experience in 16th-century convent life.
It brings so much humanity and context to an object that might otherwise feel distant. Once we’ve done this kind of analysis, it truly comes alive. It’s an incredible story.
How important is Pittcon for catching up with collaborators and connections and making new ones?
I’ve been coming to Pittcon since 2002 when I was an undergrad, and I’ve continued attending throughout my entire career. I’ve made some lifelong friends here—people who have supported me professionally and whom I’ve supported in return—even though many of them have 15 to 20 years more experience than I do.
The breadth of work presented at Pittcon is incredibly valuable to me. I can attend biologically relevant talks, see what others are working on, and think about how I might adapt their approaches for use in my own lab.
The expo floor is also a great resource. If there’s something I need to expand our lab’s capabilities, I can connect directly with vendors who can help meet those needs.
What's next for you in the Library of Congress?
We’re being asked to do a lot more outreach lately, and I think more people—especially within the library—are beginning to understand the kind of work we do. I’m hoping more people realize that these capabilities are available to them and that all it takes is a phone call or an email to get started.
New projects are naturally leading to more outreach and collaboration, helping to show how STEM can be applied in a library setting in ways people might not expect.
Our long-term research focuses on the degradation mechanisms of materials in the collection. We have our own research collection, separate from the library’s holdings, which allows us to perform destructive testing. It includes around a thousand volumes dating from 1500 to 1850, as well as audiotapes, wax cylinders, LPs, and various papers and parchments. We use this collection to study how materials degrade over time and to explore potential conservation treatments.
We also use this collection to ask broader research questions—like what new techniques we might need to bring into the lab, or how we can adapt our current tools to address those questions effectively.
Alongside the long-term projects, we run shorter-term research projects focused on conservation techniques. For example, if the library is preparing for a treatment, they may ask us to analyze the pigments, binding media, and substrate condition to guide the development of a conservation plan—such as treating a stain without damaging the underlying text.
We also manage a large quality assurance program. Every material that might come into contact with the collections during storage or housing is tested—before contracts are awarded and again when each order is delivered.
The preservation side of our work is also quite academic. We’ve got a number of peer-reviewed papers currently in the pipeline for publication.
We’re always looking for ways to share what we do, both internally and with the broader public. For example, we’ve participated in the science fair portion of our local Comic-Con for the past couple of years and plan to continue. This year, we’re highlighting our work with rare books and collaborating with an elementary school science teacher who’s spending a sabbatical year at the library. Together, we’re developing interactive exhibits for the New Young Readers Center, The Source, and our team of scientists.
One project involves a 1705 volume we analyzed for pigments. Now, the teacher is creating an interactive piece that shows the different pigments used and the natural materials—twigs, berries, rocks, and so on—that would have been used to make the original watercolors.
Expanding our impact in this way has been incredibly valuable—and a lot of fun. It’s something we’ve always done to some extent, but there’s definitely more energy and visibility around it now.
About Eric Monroe
Dr. Eric Monroe is the Head of the Scientific Laboratory Section in the Preservation Research and Testing Division at the Library of Congress. He received his PhD from the University of Illinois in Analytical Chemistry. Prior to coming to the Library of Congress, his research career centered on the application of analytical chemistry techniques and methods to neuroscience, virology, and materials science in both academic and industrial settin
gs.
This information has been sourced, reviewed and adapted from materials provided by Pittcon.
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