palimpsest
A manuscript consisting of a later writing
superimposed upon the original writing, which was
first removed to the extent possible. A double
palimpsest is one that has two subsequent
writings, and therefore two removals. The extent
to which the earlier writing could be removed
depended to a great degree on the ink used. Early
carbon inks, which merely lay on the surface of
the parchment, could be removed more or less
completely simply by sponging, but the later iron
gall inks were much more difficult to remove
because of the interaction with the fibers of the
tannin present in the ink. They had to be scraped
and then treated with a weak acid, such as the
citric acid of an orange. Even then traces of the
original writing remained. Wetting the parchment
in this manner softened it to such an extent that
it was necessary to treat the skin with dry lime
to make it dry and white once again. The word
"palimpsest" derives from the Greek roots meaning
"rub away again." Also called "rescript. " (143 )