This article is getting quite a bit of play in the archives/rare books world today, as well it should. Penn State biology professor Blair Hedges has developed a new technique for dating old books, prints, and maps; his "print clock" method "is similar to molecular-clock techniques used to time genetic mutations," according to the AP report.
Basically, this technique relies on comparative examinations of "line breaks" and other variations in illustrations and text. Hedges maintains that "breaks occur at a constant rate over time, irrespective of print runs," based on atmospheric deterioration of the wood, copper and other materials used to create the printing plates. Hedges studied woodblock-printed maps from Bordone's Isolario, the printers' devices from the same book, and also copperplate engravings. On the latter, Hedges concluded that the "the plates deteriorated 1 to 2 micrometers per year due to corrosion. The rate is similar to known rates for the atmospheric corrosion of copper."
This seems like an interesting system, although its application at this point may be fairly limited. Clearly it requires a rather large number of exemplars of known, dated samples to allow for comparison with the undated subject sample - many undated or unknown items today are simply not likely to have such a deep resource pool. Nonetheless, in some limited cases it could have its uses, and it's excellent to see the interdisciplinary approach taken by Professor Hedges.
Hedges' full article was published on Tuesday in the Proceedings of the Royal Society A.
