The print clock technique is new way of dating antique books. The technique was discovered in 2006 by Blair Hedges, a Penn State biology professor. Hedges who has a passion for maps and old prints, paid for and undertook his own research into this new process of dating books.
The print clock technique uses similar complicated procedures that scientists use to date mutations. Previously a book’s age was verified by analyzing the type of paper used or the book’s watermarks. With the print clock technique the age can be determined by analyzing the amount of line breaks on the same page in later or earlier editions of the same book.
Many experts think that page breaks or page fading occur due to wear to the print blocks during print runs. But the print clock technique has shown that the wear to the plates takes place when the plates are placed in storage. Deterioration to the plates in storage accounts for at least 10 extra line breaks per year.
While undertaking his research Hedges analyzed 23 copies of a book of maps called Isolario. The book’s ages ranged from 1528 to 1547, and there was also a later undated book. Hedges found that the later the book the more line breaks the book had. From this he deduced that the line breaks must have come from plate deterioration while in storage.
If the line breaks had occurred during printing, then the final copy of the third edition would have had the same amount of line breaks as the first copy of the fourth edition. This was not the case. The first copy of the fourth edition had a far greater amount of line breaks than the third edition. Using the print clock technique Hedges was able to date the undated fourth edition.
The Isolario books were all printed using wooden printing blocks. Hedges also did research on 16th and 17th century books printed using copper printing plates. He found that the copper plates also deteriorated by one or two micrometers per year. This is due to the copper plates corroding due to exposure from elements in the atmosphere.
Hedges' research on the print clock technique was published in an article in a British research journal. He states that he originally came up with the idea after studying old maps and prints while undertaking research in the Caribbean in 2005. A lot of Hedges' biological research involves molecular-clock dating of genetic mutations.
At the moment, the print clock technique has been used only to date books from the 15th to 17th century. More research will need to be undertaken to see if the process can be applied to later books. Experts seem to agree that the print clock technique is a sensible and scientific update on the current process.