using neutron activation analysis. The samples, dated 1571-1850 A.D., were collected from books of the Gennadius Library in Athens. Unwritten spaces of the books were used for the analysis. The elements Sb, Br, Cl, Co, Au, Fe, Mn, Hg, K, Sc, Na, and Zn were determined. The concentrations of Sb, Br, Co, and Mn were plotted vs. date of preparation of the examined papers and it was found that these plots exhibited maximum around 1800 A.D. An explanation for the forms of these plots was given taking into account the known evolution of paper technology. Experiments for testing the reproducibility of the method were also described. -- AATA