Parchment--The substance which is called parchment when made from sheep
or goat skins, and vellum when from those of calves, kids, or dead-born
lambs, can also be made from any other skin. The raw hide is buried for
one or two days, till the hair comes off easily; then it is taken out and
well scraped. Next a skewer is run in and out along each of its four
sides, and strings being made fast to these skewers, the skin is very
tightly stretched; it is carefully scraped over as it lies on the
stretch, by which means the water is squeezed out; then it is rubbed with
rough stones, as pumice or sandstone, after which it is allowed to dry,
the strings by which the skewers are secured being tightened from time to
time. If this parchment be used for writing, it will be found rather
greasy, but washing it will oxgall will probably remedy this fault. (See
"Ox-gall," p. 331.) In the regular preparation of parchment, the skin is
soaked for a short time in a lime-pit before taking off the hairs, to get
rid of the grease.
Catgut.--Steep the intestines of any animal in water for a day, peel off
the outer membrane, then burn the gut inside out, which is easily to be
done by turning a very short piece of it inside out, just as you would
turn up the cuff of your sleeve; then, catching hold of the turned-up
cuff, dip the whole into a bucket, and scoop up a little water between
the cuff and the rest of the gut.
[Sketch of making catgut as described].
The weight of this water will do what is wanted: it will bear down an
additional length of previously unturned gut; and thus, by a few
successive dippings, the entire length of any amount of intestine,
however narrow it may be, can be turned inside out in a minute or two.
Having turned the intestine inside out, scrape off the whole of its inner
soft parts; what remains is a fine transparent tube, which, being twisted
up tightly and stretched to dry, forms catgut.
Membrane Thread.--Steep the intestines of any animal in water for a day;
then peel off the outer membrane, which will come off in long strips;
these should be twisted up between the hands, and hung out to dry; they
form excellent threads for sewing skins together, or indeed for any other
purpose.
Sinews for Thread.--Any sinews will do for making thread if the fibres
admit of being twisted or plaited together into pieces of sufficient
length. The sinews lying alongside the backbone are the most convenient,
on account of the length of their fibres. After the sinew is dried
straight strips are torn off it of the proper size; they are wetted, and
scraped into evenness by being drawn through the mouth and teeth; then,
by one or two rubs between the hand and the thigh, they become twisted
and their fibres are retained together. A piece of dried sinew is usually
kept in reserve for making thread or string.
Glue is made by boiling down hides, or even tendons, hoofs, and horns,
for a long time, taking care that they are not charred; then drawing off
the fluid and letting it set.
Isinglass is made readily by steeping the stomach and intestines of fish
in cold water, and then gently boiling them into a jelly: this is spread
into sheets and allowed to dry. The air-bladder of the sturgeon makes the
true isinglass. (See "Paste and Gum," p. 332.)
Horn, Tortoiseshell, and Whalebone.--Horn is so easily worked into shape
that travellers, especially in pastoral countries, should be acquainted
with its properties. By boiling, or exposing it to heat in hot sand, it
is made quite soft, and can be moulded into whatever shape you will. Not
only this, but it can also be welded by heating and pressing two edges
together, which, however, must be quite clean and free from grease, even
the touch of the hand taints them. Sheets of horn are a well-known
substitute for glass, and are made as follows:--The horn is left to soak
for a fortnight in a pond; then it is well washed, to separate the pith;
next it is sawn lengthwise, and boiled till it can be easily split into
sheets with a chisel; which sheets are again boiled, then scraped to a
uniform thickness, and set into shape to dry. Tortoiseshell and whalebone
can be softened and worked in the same way.