When medieval Europeans read religious texts, what were their favorite prayers? Which sections did they return to time and time again, and which parts perpetually put them to sleep?
These questions have long seemed unanswerable, but a new method by Kathryn Rudy of the University of St. Andrews in Scotland takes them on with an unexpected approach: examining the dirt on a book’s pages.
Rudy hit on the technique when she realized that the amount of dirt on each page was an indication of how frequently the pages were touched by human hands. Dirtier pages were probably used most frequently, while relatively clean pages were turned to much less often. She determined the amount of dirt on each page and compared the values to reveal what passages were most appealing to medieval readers—and thus, what sorts of things they cared about while reading religious texts.
The densitometer used to analyze the amount of dirt on each page. Image courtesy of the University of St. Andrews
In a press release, Rudy said:
Although it is often difficult to study the habits, private rituals and emotional states of people, this new technique can let us into the minds of people from the past…[books] were treasured, read several times a day at key prayer times, and through analysing how dirty the pages are we can identify the priorities and beliefs of their owners.
To gather the data, she put a densitometer to work. The device aims a light source at a piece of paper and measures the amount of light that bounces back into a photoelectric cell. This quantifies the darkness of the paper, which indicates the amount of dirt on the page.