Monday, January 4, 2016

Paper-Thin

One of the questions we have about the numerous books that were created in the Middle Ages is: how did they turn animal skins into parchment of exceeding thinness?

Skin stretched to make parchment [source]
Simple answer? We don't know.

The pages are so uniformly thin—thinner than one would expect from calf skin—that theories have been put forth to find other sources. One of the most popular has been that the pages are from the much thinner calf uterine tissue. This would require an enormous number of female calves to be raised and slaughtered for book pages.

Others have suggested hides from other animals, such as rabbits. This, too, would suggest an enormous breeding program to produce the number of paper-thin pages  used in all the illuminated manuscripts we have, which of course is only a fraction of what would have been produced.

The obvious solution to the mystery is to determine the genetics of the parchment, but since that would require destroying part of a valuable antique—several parts, to test several pages—no one was eager to pursue that method. Science has provided a non-destructive method, however, with the aid of an old-fashioned PVC eraser. It turns out that rubbing a PVC eraser gently across the page creates an electrostatic charge that lifts proteins from the surface of the parchment. These proteins can then be examined for their genetic content.
The research, which is published in Proceedings of the National Academy of Sciences (PNAS), involved scientists and scholars from France, Belgium, Denmark, Ireland, the USA and the UK. They analysed 72 pocket Bibles originating in France, England and Italy, and 293 further parchment samples from the 13th century. The parchment samples ranged in thickness from 0.03 -- 0.28mm. [source]
It turns out that the parchments are made from several different animals, and there is no evidence of uterine skin. Unfortunately, this leaves us with the original question: How did they produce such thin parchment? Clearly, parchmenters had techniques centuries ago that we have not yet re-discovered.

G+ Followers