Old hams under pressure
You can read the age on the face of many people. It works similarly with books that come from antique printing presses and are marked by life.
Everything wears out - be it the joints of humans and animals or the corners and edges of furniture. That's just the way things are. Even when the genetic material is copied during cell division, things don't always go smoothly. Copy errors are common, and biologists can often use the changes to tell who descended from whom. Blair Hedges from the American Pennsylvania State University is one of these experts.
And Hedges has a hobby: historical prints and maps. As a lover of such papers, he is of course aware of the gaps in the dating of many of these old works: which one was produced and when? Now he has quickly transferred the knowledge he acquired in his profession as an evolutionary biologist to his hobby: he dates old works based on the quality with which they were printed.
Because printing plates also change over time - regardless of whether they are made of wood or, for example, copper - both wear out. While more and more fine cracks appear in the wood, the initially sharp contours of the metal plates flatten out more and more after a while. The cause here is less the repeated printing process and more the fact that the plates were cleaned and polished before each new use to remove traces of corrosion. That leaves traces. And so Hedges recognizes the age of the products in books or maps produced on the same printing press by the frequency of errors that occur or by the fading of the contours.
So the idea is comparatively simple. Hedges has now shown that the method has proven its worth in practice by identifying various works from the early Renaissance. For example, an atlas by Benedetto Bordone about Iceland was produced several times with one and the same wooden printing plate, which can be seen from an embossed stamp on the first page of each work: in the years 1528, 1534 and 1547. In the case of an edition, however, scholars disputed whether it now additionally arose around the year 1537 or only around the year 1570. To make his estimate, Hedges examined 23 editions of the atlases, each with 112 different prints. Through linear extrapolation, he finally came to the conclusion that the controversial work must have been created in February 1565, not two years earlier or later.
Hedges obtained similar dates for historical maps of the West Indies of Jamaica, Cuba and Hispaniola. All prints were made from the same copper plate towards the end of the 16th century. "It's a very simple method," says the American scientist. "Anyone can go to a library and take photos of the prints to examine how they have changed. And it doesn't hurt a copy!"
After these successes, the amateur historian is itching to talk about more famous works. He is thinking of two undated prints of Shakespeare's Hamlet, as well as Romeo and Juliet and works by Rembrandt.