A couple weeks ago I mentioned a new method of dating engravings and other prints devised by Penn State biology professor Blair Hedges (you can read more about the method here, in an interesting "Seed Magazine" article).
Now Terry Belanger, Director of Rare Book School at the University of Virginia, has responded to Hedges' method in a post to the Ex-Libris listserv. Belanger writes that Hedges' "theories are based on the examination of the successive editions of only three books, and though some parts of his methodology may eventually prove to be of some use when used with larger samples and taking other kinds of evidence into account, his current conclusions cannot be not be taken very seriously."
Regarding wood block prints, Belanger notes "Wood blocks do indeed wear very little as the result of the actual printing process, though they will wear and develop damage during the process of cleaning them (by scrubbing) at the end of the day's press run. Improperly stored, wood blocks can develop cracks and otherwise deteriorate over long periods of time, and there may be some correlation between the age of a block and the evident deterioration of prints produced from it, but many other factors need to be taken into account (including climate, storage conditions, and the number of impressions within in an edition) before it would be possible to posit a simple correlation between time and wear." He expresses similar concerns about copper-plate engravings, with additional attention to the action of the printing press on the plate.
Belanger's concerns are quite important, and it will be worth watching to see what (if any) response is forthcoming from Hedges.