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The new "print clock" technique is similar to the molecular-clock technique for timing the rate of genetic mutations, which Hedges uses as a fundamental tool for dating genetic material in much of his biological research.Both methods rely on large numbers of events that do not each occur at regular intervals but that, as a group, can be used to gauge the average rate of those events over time.The graph shows mean gray-level data for two prints, Cuba and Hispaniola.In addition to image analysis and conventional statistics, the method also requires at least two images with known print dates made with the same woodblock or copperplate that can be used to calibrate the print clock.
"It is a simple method to use for dating early prints and it doesn't hurt the prints— anybody can go to a library, take pictures of the prints made from wood blocks or copper plates, and analyze the changes over time." Hedges' analyses also show that changes in print quality were caused by aging of the wood and copper alone, not by the wear and tear of the printing process itself or the number of times an impression was made with a particular block or plate.
The method could reveal long-sought information about thousands of undated works printed on hand-operated presses prior to the development of modern printing methods in the mid-19th century, including works by Rembrandt and Shakespeare.