Copperplate Data (IMAGE) Penn State Caption Time-dependent change in copperplate prints. Close-ups of a small section (1/2 inch wide) of prints from two editions of an Italian Renaissance book by Porcacchi illustrate time-dependent image fading, useful for dating books and prints. The graph shows mean gray-level data for two prints, Cuba and Hispaniola. Credit Blair Hedges lab, Penn State Usage Restrictions Images must be accompanied by the credit line: Blair Hedges lab, Penn State License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.