Improvements in Dyeing and Tanning Skins.
Year: 1899

page_text: Date of Application, 25th May, 1899
Complete Specification Left, 23rd Mar., 1900-Accepted, 28th Apr., 1900
PROVISIONAL SPECIFICATION.
Improvements in Dyeing and Tanning Skins.
I, JAMES YATE JOHNSON, of 47, Lincoln's Inn Fields, in the County of London,
Gentleman, do hereby declare the nature of this invention (which has been
communicated to me from abroad by Walter Furnell Sykes, of New York, in
the United States of America, Merchant) to be as follows:
Ordinarily skins are not subjected to dyeing agents until they are tanned. My
foreign correspondent has found that untanned skins may be subjected to the action
of certain colouring-matters and then to fixing agents, as hereinafter explained,
with the result of both dyeing and tanning the skins.
The invention therefore consists in a process of treating skins for the purpose
of both dyeing and tanning them.
The colouring-matters which possess the property above referred to are sulphur
derivatives or compounds, such as the colouring-matter derived by treating
dioxy-benzenes, paradiamines, or amidophenols, with sulphur and caustic soda,
or those obtained by treating quinone, hydroquinone, toluquinone, or pyrocate-
chin with sulphur and ammonia. The group also embraces the analogous bodies
known generically as cachou de Laval," obtained by treating certain organic
substances with sulphur, caustic soda, and an organic acid, and embraces other
sulphuretted colouring-matters.
"
According to the ordinary procedure (for instance, to produce logwood-black)
the skin, after being tanned according to one of the commercial and well-known
mineral, or acid, tanning processes, is subjected to the several steps of broachen-
ing, immersing in logwood, plaiting, passing through logwood (each skin to be
handled several times) passing through black-dye bath, again through logwood,
fat-liquoring the skins, putting out, brushing glycerin on the grained side, and
after glycerin has been absorbed brushing neat's-foot oil on the grained side, and
finally drying. One of the known processes of acid, or mineral, tanning consists
essentially, in immersing the skins in chromic acid and afterwards reducing
the chromic acid, absorbed by the skin, to chromic oxide, this being effected by
the action of sulphurous-acid gas generated in a second bath composed of sulphite,
bisulphite, or thiosulphite of soda (or potash) with a mineral acid as a decom-
posing agent. The chromic acid may, however, be reduced and rendered insoluble
in other ways, (as is well known,) or the skin may be caused to take up a chromic-
oxide salt direct. It will suffice, however, to describe this invention in connection
with the first of the mineral-tanning processes hereinbefore referred to, which is
that best known and most widely practiced, and from this description it will be
evident to persons skilled in the art of mineral tanning that the invention can be
applied in connection with other processes of the same general character.
In carrying out the process according to this invention the treatment of the
skin may be proceeded with as in ordinary mineral tanning, up to, and including,
the operation of "slating." After this operation the skin is immersed in a bath
of one of the specified group of colouring-matters, or combinations thereof. The

page_text: strength of this solution will depend on the shade desired, and on the volume
of the dye-bath, and other considerations, as is well understood by practical dyers.
If, for example, the colouring-matter be that known as "Vidal black and if
a full black colour be desired, a two per cent. solution, or thereabout, will be
suitable. These colouring-matters produce all shades from a light-gray drab, or
slate colour, to a deep black, (in the case of Vidal black), or a deep brown, (in
the case of thiocatechin, or cachou de Laval). The next step (after washing)
consists in the immersion of the skin in a chromic bath, which fixes the colour.
Specifically, this bath may be composed of chromic acid, or of bichromate of
potash, and a mineral acid, or any one of the known baths used in mineral tan-
ning. The strength of this bath and the period of immersion can be such as is
ordinarily employed in tanning a skin. If a chromic-acid bath has been employed.
the next step will be the usual treatment in a reducing-bath (such as sulphite,
bisulphite, or hyposulphite of soda, and an acid) whereby the chromic compound
is rendered insoluble and the tanning of the skin completed.
The finished operations can be carried out in the manner commonly practiced.
By this invention, a great saving in time, labor, steam and materials, is effected,
as well as economy of space. Furthermore, it is found that dyeing with the group
of colours specified, previous to tanning, brings the skins into a better condition
for the latter operation than when the skins are subjected to the chromic bath
immediately after slating. It is also found that a faster colour is produced than
by ordinary methods, the colour not being affected by acids, or alkalies, and being
less affected by sunlight and exposure tests. It is also found that in the finishing
operation a saving is effected in that less glycerin and oil are required to impart
suppleness to the skin. Moreover, the skin itself is stronger and more durable.
The above-mentioned colours work in combination with each other, producing
a great variety of shades. They may also be employed as a mordant for other
colours where "topping" is required. Fancy shades, which they will not produce
alone or in combination, can be obtained by dyeing, as above described, and then
topping with vegetable, or anilin, colours, with a corresponding economy in cost
and a corresponding improvement in the quality of the leather.
Dated this 25th day of May 1899
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.
Improvements in Dyeing and Tanning Skins.
I, JAMES YATE JOHNSON, of 47, Lincoln's Inn Fields, in the County of London,
Gentleman, do hereby declare the nature of this invention (which has been
communicated to me from abroad by Walter Furnell Sykes, of New York, in
the United States of America, Merchant,) and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:-
In the ordinary process of preparing skins for the market, they are not dyed
until the preliminary tanning operations have been passed through but my
foreign correspondent has found that hides in the untanned state may be sub-
jected to the action of certain colouring matters, and, subsequently, to certain
fixing agents, with the result that the dyeing and tanning is accomplished within
the above series of operations, as hereinafter specified.
The colouring matters above referred to are the sulphuretted bodies, or com
pounds, which are produced by the action of sulphur and caustic soda, upon dioxi-

page_text: benzines, paradiamines, amidophenols and the like, or derivatives obtained by
the combined action of ammonia and sulphur upon quinone, hydroquinone, tolu-
quinone, or pyrocatechin which group also includes similar bodies known gene-
rally as cachou de Laval, derived from the action of sulphur, caustic soda and an
organic acid upon certain organic bodies containing nitrogen, such as bran saw-
dust and the like.
In the ordinary process of dyeing skins, which have been previously tanned by
any of the now well-known mineral tanning processes, say for blacks with logwood,
they are subjected in succession to a series of operations, including broachening,
immersion in the infusion of logwood, plaiting, passing again through the log-
wood bath, and repeated several times, then through a black-dye bath again
through logwood, fat-liquoring, putting-out, applying glycerine to the grain side
by means of brushing, then brushing in neats-foot oil, and finally drying.
One of the essential operations of the well known acid, or mineral, tanning pro-
cesses consists of an immersion of the skins in a solution of chromic acid, the
skins thereby absorbing a considerable quantity, this immersion is then followed
by a process of reduction which is effected by means of sulphurous acid, either
in a gas chamber, or generated in a bath from an alkaline, or other, sulphite,
bisulphite, or thiosulphite, in the presence of a mineral acid. Or the chromic
acid deposited in the skins may be reduced by other well known means, or a
chromic oxide salt may be caused to be taken up by the skins directly.
In describing this invention, however, I will confine my remarks to the first
mentioned, and generally practiced, mineral tanning processes, which will enable
those skilled in the art to which this invention relates to successfully carry it
out in practice.
In carrying out this invention precisely the same manner of proceeding is
adopted as is prescribed for the well known mineral tanning process up to.
and including, the operation of "slating," when the skin is immersed and worked
in a bath containing a group, or groups, of sulphuretted colouring matters herein-
before referred to, and of such a degree of concentration as the desired depth of
shade may require, or other considerations that may be suggested by the experi-
ence of the dyer. For instance, it may be desired to use the well known colouring
matter "Vidal black" for producing a deep black shade. Two per cent. of the
dyestuff, calculated approximately on the weight of the wet skins, will be found
a proper proportion, and by various combinations, or proportions, all shades of
grey, drab, or slate colour can be obtained, and in intensity to a black, while
deep browns can be readily obtained by means of either cachou de Laval, or thio-
catechine. After immersion the skins are removed from the bath containing the
dyestuff well washed and then immersed in a bath containing chromic acid, or
suitable proportions of bichromate of potassium, or bichromate of sodium, and
sulphuric acid, the oxidizing action of which, on the absorbed colouring matter
causes a fixation of the pigment in the interstices of the skin. If chromic acid
alone be used in this bath, the skins will have to be subjected to the action of a
reducing agent, such as hereinbefore mentioned namely, the alkaline, or other,
sulphites, bisulphites, thiosulphites, or of gaseous sulphurous acid, thereby causing
the insoluble chromium salt to form, thus completing the fixation of the colouring
matter, and completing the tanning of the skin, and without any objectionable
action on the texture of the skin, which will be found to be somewhat improved.
The various operations for finishing such dyed and tanned skins can be identi-
cally the same as are ordinarily carried out, and are in no way affected by the
process in accordance with this invention.
By the use of the said process, a great saving of time is affected, and the cost
is reduced to a minimum as there is economy in labour, steam and materials.
When skins are dyed by the process according to this invention and with the
colouring matters hereinbefore mentioned, they are in a much better condition to
he tanned than when they are previously mineral tanned and then dyed and the
colours obtained are much more permanent and durable than are those obtained

page_text: by the ordinary means. The colours which are obtained by this process are not
affected by either alkalies, or acids, and resist, to a very marked extent, the
influences of light and exposure. A considerable reduction is also effected in the
quantity of glycerine and oil used in the finishing operations to impart pliability.
The dyestuffs used in the combined process of dyeing and tanning according to
this invention act also in the capacity of mordants for many other colours which
may be used for the well known operation of "topping," while natural colours
or colours of the coal-tar groups, may be used alone, or in combination, for the
production of fancy, or "mode" shades upon ground colours of the sulphureted
groups, as described, thereby effecting a considerable reduction in the cost.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is:-
1. The herein described process of dyeing and tanning skins, by subjecting
untanned skins to the action of a sulphuretted colouring matter, or sulphuretted
colouring matters, of the groups herein specified, and then to the action of a
chromic salt in solution, substantially as, and for the purpose, hereinbefore
described.
2. The herein described process of dyeing and tanning skins by subjecting
untanned skins to the action of a sulphuretted colouring matter or sulphuretted
colouring matters of the groups herein specified, and afterwards to the action
of mineral agents in solution, substantially as and for the purposes hereinbefore
described.
3. The herein described process of dyeing and tanning skins, by first subjecting
untanned skins to the action of a sulphuretted colouring matter of the groups
herein specified, then to the action of a chromic salt in solution and then to the
action of a reducing agent, substantially as, and for the purpose, hereinbefore
described.
4. The herein described combined process of dyeing and tanning skins, by
impregnating said skins with a solution of a sulphuretted colouring matter of the
groups herein specified fixing the said colouring matter by means of a chromic
salt and reducing by means of an alkaline, or other, sulphite, bisulphite, thio-
sulphite, or with sulphurous acid, substantially as, and for the purpose herein-
before described.
1000
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.