An Improved Process for Preparing Chrome-dressed Leather for Dyeing Purposes.
Year: 1896

page_text: Date of Application, 27th July, 1896-Accepted, 19th Sept., 1896
COMPLETE SPECIFICATION.
An Improved Process for Preparing Chrome-dressed Leather for
Dyeing Purposes.
We, EDUARD AVELLIS, Merchant, and EMIL KÖSTER, Dyer both of
31 Königin Augusta Strasse, Berlin, in the Empire of Germany, 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:-
The present invention has for its object, to prepare chrome-dressed leather in
such a manner that it may also be dyed in all shades or tints with anilin colours.
This object is substantially achieved by freeing the chrome-dressed leather from
acid and then treating the same with materials containing tannin. For obtaining a
clear tint it is expedient to re-tan the leather thus prepared preferably with tartar
emetic or preparations of tartar emetic.
The. process may for instance be carried into practice in the following
manner:-
In order to first free 100 kilogrammes of chrome-dressed leather from acid,
3 kilogrammes of whiting and 2 kilogrammes of kitchen salt, or salt of commerce
are mixed with about 100 litres of water, the leather being washed therein for about
a quarter of an hour until the acid is removed, which may be tested by means of
blue litmus paper. The leather is then rinsed with water in order to remove the
chalk.
The leather from which the acid has thus been removed is now treated with
materials containing tannin. When use is for instance made of divi-divi we
prefer to employ for 100 kilogrammes of chrome-leather 1 kilogramme of tanning
material to form a solution of 1 to 2 degrees Baumè. For lighter tints we use
correspondingly weaker liquors. In this liquor the leather remains for about
half an hour after which the grain is dyed.
The leather thus prepared may be dyed at once. However, in order to obtain
clearer tints it is advisable to re-tan the same with tartar emetic.
For chrome-dressed sheep-skin and kid-leather we employ 1 gramme of tartar
emetic for three litres of liquor per skin; for calf-skin 1-5 to 2 grammes for 6 litres
(according to the size of the skin); and for cow-hide 6 to 10 grammes for 10 to
18 litres. The tan is used at 36 degrees Centigrade. The leathers remain in the
fulling-barrel for from 5 to 8 minutes. The tanned leathers are rinsed in clear
water for a short time and then dyed in a trough or fulling barrel with the desired
colouring matter.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1st. A process for preparing chrome-dressed leather for dyeing purposes, by
first freeing the leather from acid and then treating the same with materials
containing tannin, substantially as described.

page_text: 2nd. In the process described in the first claim the use of tartar cratic or a
preparation of tartar emetic for re-tanning the prepared leather substantially as
described.
Dated July 27th 1896.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicants.