Vermont phÅ“nix. [volume] (Brattleboro, Vt.) 1834-1955, 1882-10-20
tFrom tho Boston Journal Of obemistry.l

The manufacture Of leather is chemical
process, although leather had been made be-
fore chemistry was acknowledged a science !;
and tribes Of people who know but little about
civilization are convcrsant with means for
converting skins into leather or at least of
rendering them pliablc and durable, this be-
ing the two-fold object of tanning. 1t is but
recently that our knowledge of the anatomy
of the skin and the action of chemicals there
on has been sufficiently accurate to place the
art of tanning among the chemical industries.
The skin of man and animals consists Of
two layers the epidermis or cuticle, without,
and the dcrma, or true skin, beneath. The
cpidermis is hard and horny on the surface,
especially on the hands and feet. 1t may, in
fact, be divided into two layers; the outer,
which is dead and without sensation or the
power of reproduction, and the inner, where
successive layers arc being formed to take the
place of those destroyed. 1t is, however, the
true skin, or derma, which is employed for
making leather. This also consists of two
layers; the corium, or deep stratum, and the
papillary, or superficial layer.
The first operation is, in most cases, the
removal of the hair, unless, as in the case of
furs, the skins are to be tanned with the hair
on. Milk Of lime, sulphurct of calcium, and
mechanical means are employed to remove
the hair and epidermis. Afterward, the skins
are placed in a sour infusion Of barley or rye
meal. This sets up a kind of fermentation,
which destroys the cellular tissue in which
! the hairs are rooted, 50 that both hair and cp-
| idcrms are easily removed by scraping
The process of converting the hide strip
| ped Of all useless parts, epidermis, fatty It's
sue, etc, into leather may be considered un-
d.
| ing, oiling and limc-curing In the common
process of red tanning a vegetable substance
| is employed, to which is given the name OF
tannin, or tannc acid This substance, when
| pure, has an astringent taste, precipitates So
| lutions Of gelatine, and yields with salts of
| iron black or green precipitate, frequently
used suspended in dilute gum water, for
writing-ink. In tanning different substances
are employed, such as oak bark, sumach,
| divi-divi catechu, etc. Oak bark contains
| from 10 to 10 per cent Of tannic acid. The
| bark is cut in small pieces, and is then known
as tan bark, or simply '"tan." Pine-treC
bark is also a good material, containing about
| per cent. Of tannin. In this country it is
less frequently employed than hemlock bark.
Sumach grows wild in many parts Of our
| country, and should find extensive use in tan
ming, but requires care in regard to the time
and method Of collecting it. 1t contains from
| u to l6 per cent. of a substance closely re-
sembling the tanniC acid in nut-galls, besides
small quantities Of gallic acid, and also yel-
! low dye stuff.
| When a hide has been thoroughly cleaned
on the flesh side by soaking in water and
scraping, on the hair side by sweating oi
| liming--thc pelts are ''raised,n the lime
compounds removed, and the fbres of the
skin swollen up so that they can more readi
ly absorb the tanning material. This raising
or swelling is done by placing it in a soul
bath of wheat or barley, where Tactic fermen
tation is going on. The various acids, lactic
formic, acetic, butyric, etc, thus formed
cause the pelt to swell to double its usua
thickness. In two weeks time this opera
tion is completed, and the hide is ready fol
the action of fannie acid. This is usually eff
fected in watts sunk into the earth, where tan.
bark and hides are arranged in alternate lay.
ers, and the whole saturated with water. Tho
first time they are left in the vat 8 or 1C
weeks; after taking them out and renewing
the tan-bark they are put in again for three
or four weeks the third lasts still longer
and in case of a very heavy hide fourth
and even fifth, immersion is necessary, re
| quiring nearly two years in all. For light anC
thin skins a cold water extract of the tanning
material is employed and the whole opera
ton is finished in two or three months.
Russia leather is made from the hides o.
two or three year-old calves. The tanning
material employed is willow bark, sometime!
also pine and pear bark, used either in watts o
in the form of extract. The operation lasts
five OF six weeks. When this is completed
the leather is well rubbed on the flesh sid,
with birch oil and oil from sea-cavcs, t
which it owes its peculiar odor, and then i
passes through rollers that impress upon it
peculiar figure and rOughness.
Morocco, or Turkey leather, is fine, soft,
dyed leather, tanned with sumach. For gen
uine morocco the hide of goats is used, while
split sheep and thin calf skin are converted
into an inferior morocco for book binders use
The dye is applied to one side only, either by
|. a brush or by dipping. The best morocco il
dyed before it is tanned. Recently analint
colors have been largely used for dyein!
leather, both morocco and siivers (split sheep
skim Roam is sheep-skin tanned like moroc
co, but wanting the grain given by groovet
rollers.
Glove kid is made from the skins Of younl
goats or lambs. The grain is not removed
rs with wash-leather or undressed kid. Tn
prepared skins are placed in paste made o
wheat flour, yolk of eggs, alum, common sal
and water. This not ouly tans it, but the oi
of the egg renders it pliable and gives it tn
property of modelling itself to the hand. Tn
kid is generally dyed on the grain side.