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There is a serious limitation to the “print clock” technique described in this article that can probably be addressed. The method proposed holds good only for works with small print runs (such as expensive maps), where the damage to the printing surface in successive printings is minor in comparison to deterioration over time. Damage to the printing surface in the same run has already been studied in the case of Shakespeare’s early folio texts, and can be significant. If researchers combine the data for two very different physical processes—deterioration owing to pressure on surfaces and repeated use and deterioration over time—the results will gain a great deal of accuracy.

Anthony Guneratne
Jacksonville, Fla.