In
Medieval Europe, prior to the
introduction of paper*, the
preparation of
writing surfaces was a difficult business.
Parchment and
vellum, two of the most common and
most expensive writing surfaces in use at the time, were actually the stretched, cured, and cut
skins of sheep or goats. The result was that
scholars and
monks were
chronically short of these essential materials.
The solution was to scrape the ink off of existing manuscripts, creating what are now known as "palimpsests." The manuscripts chosen for scraping were usually the ones considered to have the least value, and in the monasteries of Medieval Europe this all too often meant the secular works of ancient or antique Greek and Roman authors.Thus, a monk in need of paper for his florilegium (a kind of journal about the religious materials he was reading) might grab the monastery's copy of, say, Sophocles' plays and scrape away. It is difficult to know how many manuscripts were lost to history in this way, but the answer is probably larger than we'd like.
Often, traces of ink would remain on the scraped parchment, and thus it would be recognizable as a palimpsest. But this was rarely enough for document scholars to make headway with. The advent of x-ray technology, however, was a massive boon to such scholars: until then, they had to rummage through musty libraries in order to hope of finding a new and undiscovered manuscript; now, they could just x-ray palimpsests and see what was there. It's rare that technology can truly bring lost knowledge back from the dead, but in these cases that's often what happened. (Early chemical processes were used to help restore scraped texts but the x-ray method has proved much more profitable).
*This came about as a result of the
Christian reconquest (known as the "
Reconquista") of
Muslim Spain, which is bracketed roughly by the capture of
Toledo in
1085 and the
explusion of the
Moors from
Granada in
1492. The
Muslims, of course, learned the art of
papermaking from the
Chinese some time earlier.