. Then the back sheet can be peeled off as
well, leaving the damaged sheet to dry.

The following is quoted from "Chambers' Encyclopaedia" on Gelatine:--

"Gelatine should never be judged by the eye alone.

"Its purity may be very easily tested thus: Soak it in cold water,
then pour upon it a small quantity of boiling water. If pure, it will
form a thickish, clear straw-coloured solution, free from smell; but
if made of impure materials, it will give off a very offensive odour,
and have a yellow, gluey consistency."

WASHING

When there are stains or ink marks on books that cannot be removed by
the use of hot size or hot water, stronger measures may sometimes have
to be taken. Many stains will be found to yield readily to hot water
with a little alum in it, and others can be got out by a judicious
application of curd soap with a very soft brush and plenty of warm
water. But some, and especially ink stains, require further treatment.
There are many ways of washing paper, and most of those in common use
are extremely dangerous, and have in many cases resulted in the
absolute destruction of fine books. If it is thought to be absolutely
necessary that the sheets of a book should be washed, the safest
method is as follows:--Take an ounce of permanganate of potash
dissolved in a quart of water, and warmed slightly. In this put the
sheets to be washed, and leave them until they turn a dark brown. This
will usually take about an hour, but may take longer for some papers.
Then turn the sheets out and wash them in running water until all
trace of purple stain disappears from the water as it comes away. Then
transfer them to a bath of sulphurous (not sulphuric) acid and water
in the proportion of one ounce of acid to one pint of water. The
sheets in this solution will rapidly turn white, and if left for some
time nearly all stains will be removed. In case any stains refuse to
come out, the sheets should be put in clear water for a short time,
and then placed in the permanganate of potash solution again, and left
there for a longer time than before; then after washing in clear
water, again transferred to the sulphurous acid. When sheets are
removed from the sulphurous acid they should be well washed for an
hour or two in running water, and then may be blotted or squeezed off
and hung up on lines to dry. Any sheets treated in this way will
require sizing afterwards. And if, as is often the case