Improvements in Tanning.
Year: 1898

page_text: Date of Application, 24th Nov., 1898
Complete Specification Left, 23rd Aug., 1899-Accepted, 14th Oct., 1899
Improvements in Tanning.
I, JOHANN VICTOR KOCH, of Weile Der Stadt, in the Kingdom of Wurtemburg,
Germany, Tanner, do hereby declare the nature of this invention to be as
follows:-
According to the process hitherto known for tanning with chromium com-
pounds etc., no leather could be produced which had a sufficiently smooth surfcae
on the flesh side to enable it to be capable of being polished so that it could be
utilised for boots and shoes with the flesh side outwards. A further drawback
of chrome tanned leather was that when once dried it could no longer be
uniformly coloured. The process hereinafter described enables a product to be
produced by means of a specially combined chromium and vegetable tanning
whereby the said product is suitable not only for ordinary leather but also for
brown and black polished leather and which product possesses all the advantages
of the brown and black polished leather tanned entirely with vegetable tanning
materials and especially the advantages of the best shoe upper leather combined
with those of chrome tanned leather, and which further can still be uniformly
coloured after drying. For the preparation of this improved leather the hides
having been cleansed as usual and freed as far as possible from lime are then
placed in a lukewarm gradually concentrated bath of basic chrome alum and then
in a likewise lukewarm bath of basic oxychloride of chromium with increasing
concentration, throughout which they are constantly agitated and finally well
washed. They are then subjected to a vegetable tanning in diverse colours and
finally further treated as usual in the case of polished leather, brown leather, and
fancy leather.
The special novelty of this process consists of the consecutive order and nature
of the baths, for it has been proved by experiment that the obtaining of the new
technical results can only be attained by the process above characterised and
hereinafter illustrated by way of example, and not by any other course of opera-
tion or by the omission of one or the other baths any more than by following
one of the hitherto known methods of tanning. This new technical effect
results in the production of a brown or polished leather possessing the toughness
of chrome-tanned leather. The process can of course be easily adapted for the
production of smooth, fancy, or coloured leather. By way of example, 5 kilos
of chrome alum are dissolved in 15 litres of water and decomposed by means of
a solution of 2 kilos of calcined soda dissolved in 5 litres of water. This mixture
is gradually added into a vessel partially filled with water at a temperature from
30 to 35 degs. Centigrade in which water about 30 cleansed hides free from lime
are agitated for about 4 hrs. The hides are then treated in a like manner in
a second bath; the second bath is prepared with one kilo of oxyhydrate of
chromium which is dissolved in about 5 litres of hydrochloric acid, and is decom-
posed with soda solution until basic oxychloride of chromium separates. The
hides are then beaten up, worked on the flesh side, kneaded for 1 hr. in the

page_text: kneading trough, washed, and are then subjected to a vegetable tanning in
various colours, the first whereof requires for each skin 1/2 kilo of sumach,
and kilo gambier, the second ½ kilo sumach, 5 kilo gambier and ½ kilo
oak bark, the third and fourth each one kilo of oak bark and 1/2 kilo quebracho
wood. In these colours the hides are then thoroughly stirred about, and remain
therein with frequent agitation with each colour for about 6 days. They are
then squeezed out and are worked for polished leather.
I, JOHANN VICTOR KOCH, of Weile Der Stadt, in the Kingdom of Wurtemburg,
Germany, Tanner, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
According to the process hitherto known for tanning with chromium com-
pounds etc., no leather could be produced which had a sufficiently smooth surface
on the flesh side to enable it to be capable of being polished so that it could be
utilized for boots and shoes with the flesh side outwards. A further drawback
of chrome tanned leather was that when once dried it could no longer be
uniformly coloured. The process hereinafter described enables the product to be
produced by means of a specially combined chromium and vegetable tanning
whereby the said product is suitable not only for ordinary leather but also for
brown and black polished leather and which product possesses all the advantages
of the brown and black polished leather tanned entirely with vegetable tanning
materials and especially the advantages of the best shoe upper leather combined
with those of chrome tanned leather, and which further can still be uniformly
coloured after drying. For the preparation of this improved leather the hides
having been cleansed as usual and freed as far as possible from lime are then
placed in a lukewarm gradually concentrated bath of basic chrome alum and then
in a likewise lukewarm bath of basic oxychloride of chromium with increasing
concentration throughout by which they are constantly agitated and finally well
washed. They are then subjected to a vegetable tanning in diverse colours and
finally further treated as usual in the case of polished leather, brown leather and
fancy leather.
The special novelty of this process consists of the consecutive order and nature
of the baths, for it has been proved by experiment that the obtaining of the new
technical results can only be attained by the process above characterized and
hereinafter illustrated by way of example, and not by any other course of opera-
tion or by the omission of one or the other baths any more than by following
one of the hitherto known methods of tanning. This new technical effect
results in the production of a brown or polished leather possessing the toughness
of chrome-tanned leather. The process can of course be easily adapted for the
production of smooth, fancy, or coloured leather. By way of example, 5 kilos
of chrome alum are dissolved in 15 litres of water and mixed with a solution
of 2 kilos of soda ash dissolved in 5 litres of water. This mixture is gradually
added into a vessel partially filled with water at a temperature from 20 to 35°
Centigrade, in which water about 30 cleansed hides free from lime are agitated

page_text: for about 4 hours. The hides are then treated in a like manner in a second
bath; the second bath is prepared with 1 kilo of oxyhydrate of chromium which
is dissolved in about 5 litres of hydrochloric acid, and is decomposed with soda
solution until basic oxychloride of chromium separates. The hides are then
beaten up, worked on the flesh side, kneaded for one hour in the kneading trough,
washed, and are then subjected to a vegetable tanning in various colours, the
first whereof requires for each skin 2 kilo of sumach, and ½, kilo gambier, the
second kilo sumach, 1 kilo gambier and 2 kilo oak bark, the third and
fourth each one kilo of oak bark and kilo quebracho wood. In these colours
the hides are then thoroughly stirred about, and remain therein with frequent
agitation with each colour for about eight days. They are then squeezed out
and are worked for polished leather.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
Process for the production of polished leather, of brown and other kinds of
leather, of rapid tanning of animal skins by means of combined vegetable and
a chromium tanning which consists in treating the crude skin successively with
a solution of basic chrome alum, basic oxychloride of chromium and vegetable
tanning material.
1
00
1000
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester and Birmingham.