Tuesday, July 25, 2006

New Article on Hedges

Philadelphia Inquirer reporter Tom Avril has published an article on the new method of dating rare prints and engravings offered by Penn State biology professor Blair Hedges (my original post on the subject is here, with Terry Belanger's followup criticism here). Avril discusses the response to Hedges from within the rare book community (including Belanger's critique) and offers Hedges' rather glib response to it: "I would feel the same way if somebody from their area came into mine."

Avril does a good job of summarizing Hedges' method, and offers some interesting insights into his methodology as well:

"Printing pressure had no impact on copper plates, he says. Immense pressure would have made the grooves wider, not narrower. To prove this point, Hedges bought a new copper plate and engraved some lines in it. Then he covered it with a steel plate and drove over it with his SUV. No change in the engraved lines. Finally, he pounded the plates with a sledgehammer, exerting considerably more pressure than what would come from a printing press. Sure enough, the lines got wider, not thinner."

The article concludes by noting that Hedges is now working his method on the undated fourth quarto edition of "Hamlet." I hope that doesn't include running it over with his car.

1 comment:

bh said...

Dear Mr. Dibbell,
I just ran across your blog posting from July 25th regarding my work on dating books and prints. responded to Belanger's criticism on Book_Arts (and simultaneously on Ex-Libris) two weeks before your own posting. He was incorrect.
Here it is:
From: Book_Arts-L [mailto:BOOK_ARTS-L@LISTSERV.SYR.EDU] On Behalf Of Blair Hedges
Sent: Friday, July 14, 2006 12:08 PM
To: BOOK_ARTS-L@LISTSERV.SYR.EDU
Subject: Re: [BKARTS] Dating prints: correlating age and wear

I thank Professor Terry Belanger for his critical comments. It is natural to be skeptical about any new method and only time will tell how whether this one is generally useful or not. However, he is incorrect about his major point regarding copperplate wear (see below).

I encourage anyone interested to look at the scientific article describing the method, for a complete description, rather than popular news articles which may skim over the evidence. This web site has a PDF of the article:
http://evo.bio.psu.edu/printclock/

Copperplate Wear
I presented evidence that copperplate wear (narrowing of lines) came from abrasion (polishing) of the plates to remove time-generated nicks and corrosion and not from compression by the printing press as generally assumed. Professor Belanger disagrees and supports the "universally held"
hypothesis of plate compression, causing an "ironing-out effect" that he says will narrow the grooves/lines.

But this is not what happens when metal is compressed. Just like a ball of pizza dough when rolled, it expands as it becomes flatter. For example, if a copper penny is placed on a railroad track and is compressed by a train, it becomes much wider than a normal penny (also, the same occurs if you strike a penny with a large hammer). It logically follows that any grooves in a copperplate that is compressed will become wider, not narrower.

To prove this point I used a burin to engrave a grid of grooves in two small copperplates. I compressed one and eroded the surface of the other. All lines in the compressed plate became wider and all in the eroded plate became thinner, as predicted (see graph:
http://evo.bio.psu.edu/printclock/#CopperplateTest). I also made precise measurements of different editions of Renaissance prints showing that there was no expansion of print dimensions and hence no measurable compression of the copperplates by the rolling printing press (see article). Thus the universal assumption of copperplate compression is rejected.

Other comments:
Number of impressions: The total number of impressions made from a single Renaissance copperplate during its lifetime was essentially unknown until the study by Bowen and Imhoff (2005) revealed 18,257 impressions for one plate from the Plantin Press. Previous estimates ranged from a few hundred to a few thousand, but most of those were tied to limited print runs and anecdotal comments, not actual documents from the press itself. Professor Belanger is not persuaded that the larger number from Bowen and Imhoff is representative, and favors the smaller numbers. But even if the larger number proves to be an exception, it nonetheless shows that a copperplate was capable of producing a very large number of impressions. In turns, this adds support to the hypothesis that the printing press may not be the sole or even major culprit in "wearing out" the plate.

Print runs of books: here I think Professor Belanger misunderstood the methods, because nothing in my study is "dangerous" (I hope!). For one of several statistical tests - not a critical aspect of the study - I needed to estimate the *relative* numbers of books from different editions, and did this by consulting global catalog sources (WorldCat etc.) and contrasted that by assuming a constant number per edition. *Absolute* numbers were not needed, and if Professor Belanger can recommend a better method I am open to suggestions.

Climate and storage conditions: Many factors will affect the deterioration of both woodblocks and copperplates, and I noted these in the article. Too little information is available yet to know how much variation exists. But the method works by comparing prints from the *same* plate (usually same printer and location), not from *different* plates or from different printers, and thus Professor Belanger overstates the nature of the variability. He also includes "number of impressions" which was a factor that I excluded with statistical tests.
Blair Hedges
________________________
S. Blair Hedges, Ph.D.
Professor of Biology
Pennsylvania State University
208 Mueller Lab
University Park, PA 16802-5301
tel. 814-865-9991
http://evo.bio.psu.edu/hedgeslab/