This post is coauthored by Kelsey Beeghly, the 2023-2024 Albert Einstein Distinguished Educator Fellow at the Library of Congress, and Meghan Hill, preservation science specialist. It is the first in a series focused on the science being done at the Library, inviting students to explore the research methods the scientists use.
What do an artist, a scientist, and a curator housing important political cartoons have in common? A desire to preserve Herbert Block’s collection of more than 10,000 sketches that are housed at the Library of Congress. Using multi-spectral imaging that captures light across bands of the electromagnetic spectrum that are not visible to humans can reveal information that helps the Library protect the important work from damage and degradation. Recently, Meghan Hill worked to understand how the unique pencils and pens used in Herblock’s sketches fade during light exposure, in order to provide information that can be used in decision-making about if and how to exhibit individual items. Through observing processed and unprocessed images and a video, students can explore these concepts for themselves using the Library’s free resources.
Preservation science brings together many different disciplines. When it was time to decide on college, Meghan faced the dilemma of enjoying academics like science and math but also wanting to pursue her passion for art. Ultimately, she chose art history and eventually decided that she wanted to be a curator in an art museum. Through internships she was introduced to preservation science – something that occurs behind the scenes at every institution, but most people aren’t aware of – and knew that was the perfect marriage of her interests and talents.
Modern media can be more of a challenge to preserve, as compared to more stable pigments, like those used since cave paintings, due to their rapidly changing ingredients and varying standards of quality for mass production. They also tend to be light sensitive, which is an important consideration for when the cartoons are exhibited to the public. When the curator raised these concerns, the Library’s Preservation Research and Testing Division (PRTD) went to work to identify which pens – and Herbert Block, also known as Herblock, used many different ones! – were at risk of degradation, and more importantly, why. If they could understand the degradation mechanisms, they would know the best conditions for the cartoons’ long-term storage.
Students can also explore concepts related to the ways in which materials change over time. After a discussion about the electromagnetic spectrum and how different materials reflect certain wavelengths of light, show students this image of a 10th century parchment fragment. Students might observe the adhesives as well as the faded condition of the parchment.
Next, show students the second image produced using spectral imaging and image processing, which has emphasized and assigned a false color to different components like the parchment, inks, pigments, stains, and adhesive residue around the edges, making them more visibly evident. Each component has unique spectral responses because they’re made from different chemical compositions. How many different colors can students observe in the image now? Ask students to hypothesize what element of the parchment might be represented by the different colors, and what information this could potentially reveal about the parchment.
Because the Library has access to Herblock’s original writing utensils, this type of analysis on his cartoons allows us to identify which pen he used and conduct further tests using that pen to see how it reacts to light. Ask students: Why do you think the information gained from image processing about the type of pens used by an artist is crucial to a curator who plans to put it on display?
This video takes students along into the imaging lab for Meghan’s investigation of a Herblock cartoon. After watching, ask students to discuss how understanding the electromagnetic spectrum is important to her work.
Being able to characterize Herblock’s materials, from the paper to the pens, enabled PRTD to see trends in time periods when Herblock introduced new types or brands of materials into his repertoire. It was incredibly helpful to be able to suggest more specifically which cartoons, out of thousands that spanned the course of decades, may need special consideration before being exhibited.
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