During Castle’s Freshman Imaging Project, the students created a polynomial texture mapping device, which allows imaging scientists to study the texture of an old document. Dr. Fenella France, chief of the Preservation Research and Testing Division at the Library, was invited to speak to the class and Castle became intrigued by her work. Later, she visited France’s lab during a vacation to Washington, D.C.
Inspired by her visit, Castle applied for and received an internship in the Preservation and Testing Division at the Library of Congress in Washington, D.C. to work on three separate projects using spectral imaging at ultra violet, visible, and near-infrared wavelengths. CIS Professor Roger Easton agreed to fund the internship last summer.
“Maggie's interest was fortuitously timed, as I had spent the summer of 2011 at the Library helping to develop some of the techniques used to process the imagery,” Easton said. “The value of such an opportunity to an undergraduate student is incalculable, and she will find that the techniques she utilized are applicable in a wide range of disciplines, including medicine and environmental remote sensing."
Initially, Castle delved into assisting experts in figuring out the origins of the nautical diary of 15th century German mathematician and astronomer Johannes Müller von Königsberg (1436-1476), known as Regiomontanus. The diary consisted of a collection of astronomical calculations and sketches that paved the way for the transition from the Julian calendar to the Gregorian calendar, which we presently use, in 1582. Castle used spectral imaging to extract watermarks in an effort to determine where and when it was printed. She found four watermarks and “hidden text” on six of the 15 imaged pages.
“The challenge was there was a lot of guess and check work,” Castle says. “After using the software, you had to experiment with different bands to try to get the watermark to pop out and visually discern it from the background.”
For her second project, part of an effort to preserve the diary and other documents from the same time period, Castle was charged with investigating the reactivity of iron gall ink, also using spectral imaging. This would help preservation scientists select a method to assess treatments for stabilizing ink on historic documents. Iron gall ink, made from iron salts and tannic acids, was common during this time period up to the 20th century. Iron (II) sulfate heptahydrate, contained in the ink, is corrosive to paper. Castle was able to figure out, using a spot test, the percentage of reactive Iron(II) in test prints to create plots depicting the change in this percentage over time for various preservation methods.
Finally, Castle had the extraordinary experience of working with a 1513 edition of the Ptolemy Atlas, one of three copies of this rare book published by Johannes Schott in Strasbourg. The goal was to figure out which pigments had been used in hand-coloring the map. Once again, spectral imaging allowed Castle to examine the document non-invasively and to separate the image set into a set of spectra that can help determine the mixture of pigments at point (pixel) on the image. She then compared these spectral curves and compared them to existing pigment samples. In the final weeks of the internship, Castle discovered that fustic, a yellow, might have been used.
”Maggie Castle showed great enthusiasm for her work in the Preservation Research and Testing Division, and a true appreciation for the uniqueness and importance of these rare collection items at the Library,” Dr. France said. “Many people ask what is the most challenging part of what we do, and I often answer, that there is no room for mistakes; objects we are working with are often the only copy remaining in the world. Maggie’s background in imaging science provided an excellent grounding for the work we do here at the Library, and we were delighted to have her as part of our preservation team over summer.”
While Buffalo native Castle wouldn’t mind returning to Washington D.C., where her sister lives, she needs to buckle down and work on her senior project next summer.