On April 23, 2012 the website of the University of St. Andrews in Scotland published an article entitled Dirty books reveal secret lives of people living in mediaeval times. This article described a technique invented by Kathryn Rudy, professor in the School of Art History at St. Andrews, of using a densitometer to measure the dirt levels on pages of medieval books of hours, showing which pages were most read, leaving dirty residue.
"Dr Rudy’s new technique with the machine, used on mediaeval prayer books, has shown people were as self-interested, and afraid of illness as today.
"The ground-breaking research has even managed to pinpoint the moment that people fell asleep reading the same book.
"For example one of the dirtiest pages in a selection of European religious books was a prayer to St Sebastian who was often prayed to because his arrow-wounds (the cause of his martyrdom) looked like the bubonic plague.
"This shows us that the reader of the book was terrified of the plague and repeated the prayer to ward off the disease.
"Similarly pages which contained the prayers for the salvation of others were less dirty than those asking for salvation for oneself.
"As well as demonstrating mediaeval people prayed for their own assistance, the analysis showed the pages of a prayer to be said in the small hours of the morning were only dirty for the first few pages.
"Dr Rudy extrapolates that it shows most readers fell asleep at the same point.
"She 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.
“ 'Religion was inseparable from physical health, time management, and interpersonal relationships in mediaeval times. In the century before printing, people ordered tens of thousands of prayer books—sometimes quite beautifully illuminated ones—even thought they might cost as much as a house.
“ 'As a result they 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' " (http://www.st-andrews.ac.uk/news/archive/2012/Title,85210,en.html, accessed 06-23-2012).