Improvements in Tanning..
Year: 1894

page_text: Date of Application, 8th Nov., 1894
Complete Specification Left, 30th July, 1895-Accepted; 28th Sept., 1895
Improvements in Tanning..
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 com-
municated to me from. abroad by Friedrich Kornacher, Technical Expert and
Journalist of Frankfort-on-the-Main, and 'the Firm of Diesel & Weise of Poessneck,
Manufacturers both in the Empire.of Germany) to be as follows:-
The object of this invention is to accelerate the manufacture of thoroughly
tanned leather, and it mainly, consists in submitting skins or hides, before.they are
steeped in the actual tanning.solution to a preliminary treatment calculated to work
the skins or hides into a state of readiness for the subsequent tanning process
which may be then fully carried out within a very small space of time, say, a few
hours.
The preliminary treatment referred to partly consists in what is termed "mineral
tanning." Attempts have already been made to subject skins or hides to the action
of minerals before treating them with tans and the product obtained by this process
was known as "half-tanned" leather, which however in the opinion of specialists
was deficient in quality (see the Vienna periodical "Die Weissgerberei" p. 298)
and consequently soon disappeared from the market.
Now the leather. obtained by the improved process described in this invention
is not half-tanned but completely tanned leather and does not in any way differ
from leather tanned by any of the ordinary known processes.. The improved
process does not merely replace the so-called "mineral" tanning in a partial
or superficial manner, but is adapted thoroughly and completely to supersede
mineral tanning, so that no vestiges thereof remain behind or are traceable in the
leather obtained as a final product.
This result is attained by several manipulations which have some connection with
mineral tanning.
The following is a description of the process carried out as a whole, according
to this invention.
The hides or skins prepared substantially in the manner as hitherto but if
desired somewhat more lined and oozed and very carefully cleansed are first
tinctured with a weak acidulated tanning decoction or solution. The object of
this operation is partly to enable the grain of the hides or skins more. effectually
to resist subsequent reactions and partly to remove the particles of lime which
would otherwise remain behind in the hides or skins and interfere with the
operations which are to follow. The skins or hides thus tinctured and thoroughly
washed are then treated. by the well known mineral process and after undergoing
the treatment with the accessory operations involved they are again slightly
washed.
After this process the hides or skins in place of being. immediately, submitted to
the action of tan as has been usual hitherto are first treated in a preliminary
operation which is of the greatest importance and absolutely necessary if thoroughly
tanned leather is to be obtained. To this end the.hides or skins after undergoing
the mineral treatment are lightly washed, dried, pared or split, and if necessary,
stretched or otherwise dressed or prepared according to the nature of the leather
to be produced.

page_text: By this and the subsequent operations the skin or hide is opened or made
porous and capable of absorption to such an extent that the vegetable tanning
process, which is now to follow, may be performed completely in about as many
hours as has taken mouths hitherto to complete while at the same time any tangible
or appreciable trace of the previons mineral tanning is entirely done away with.
The paring, splitting or other dressing of the leather may, if preferred, be
proceeded with in the course of the tanning process itself, in which case these
operations are performed after the fresh tanning operation has been started, the
skin being once more dried for the purpose. Heavy skins or hides may, after
undergoing the first stage of tanning, be dried, pared, or split, and they are
preferably tauned in a vat which is so arranged that the said skins or hides may
be tightly stretched in frames before being steeped in the tan.
દ
As a strong tanning solution. or ooze "is employed at the very outset of the
process it is advisable to rub fat or the like into the grain of the skin before it is
placed in the tanning solution. By such means the delicate layer or film which
forms the grain is protected from too energetic an action of the solution and
prevented from becoming hard and liable to split or crack; while at the same time,
in consequence of the fat or the like which gradually issues from the skin, being
transformed into a delicate substance of the nature of an emulsion, the absorption
of the tan by the skin, far from being delayed is on the contrary very materially
promoted.
Another essential condition, on which the rapid and thorough completion of the
tanning depends, is that the tanning solution employed should be slightly acidulated,
whereby the skin is made to swell and its pores are opened so that it may more
readily absorb the tanning liquid.
The skin prepared in the manner described is now placed in the acidulated
tanning solution which should not be far below 3° or 4° Baumé, as regards density
or strength and which is heated to from 30 degrees to 50 degrees Centigrade.
While in this solution the skins or hides are constantly stirred for which purpose a
rotary drum should in preference be used. In a short time after commencing the
operation, it will be found that the solution of tan has become saturated with the
mineral salts which have been expelled or eliminated from the skins or hides and
the solution must then be at once renewed. This renewal of the tanning solution
may be repeated several times until it is found that the liquid after the skins or
hides have been treated therein for a considerable space of time no longer contains
an appreciable proportion of mineral salts or kindred matter.
The tanning takes place in any suitable apparatus such as a fulling tank or vat
or the like, in which, by means of any suitable arrangement the tanning solution is
maintained at the desired temperature and which should enable the liquid to be
readily discharged and renewed.
The admission of fresh supplies of tanning liquid is preferably effected by means
of a pipe connected with an extraction battery and extending into the vat or the
like through the hollow shaft or trunnion of the latter and in this manner the skins
may be fed with fresh tanning liquid during the rotation of the vat (which may be
cylindrical) whereby tauning is also assisted.
The vegetable tanning material employed is, as usual, in the condition of an
aqueous solution. Its composition depends on the nature of the hides or skins
which are to be tanned and the purposes for which the leather is required whether
of a finer or coarser quality such as for example either for the manufacture of boots
and shoes, or for saddle and harness making purposes indeed the tauning compound
may vary in a manner corresponding to the variations involved in the usual practice
for similar purposes.
By the process herein described comparatively light hides and skins may be
thoroughly tanned in a few hours and the heavier sorts in one or more days, aud
the leather obtained in this manner does not differ, either in appearance, in quality
or in weight from the leather tanned by the long and tedious tanning methods
hitherto in use.

page_text: The treatment of the hides or skins by mineral salts does not constitute the
main object of the process, but is employed in conjunction with the other manipu-
lations hereinbefore described, for opening the pores of the skin or hide, while all
traces of such mineral treatment are entirely obliterated in the subsequent phases
of the process. Such mineral treatment may if preferred be replaced by other
operations capable of serving the purpose which the mineral salts are employed, viz.,
that of rendering porous the hides or skins under treatment, provided that the
agents employed in carrying out such operation may subsequently be eliminated
from the hides or skins by the action of the heated tanning solution or liquid.
Other means which will serve also this purpose are known under the names of
9966
soap tanning glycerine tanning" and "fat tanning." When one of these said
means is employed as a substitute for the "mineral tanning" the remaining portion
of the process remains unaltered, except that, where the fatty method is used it is,
of course, unnecessary to grease the skins or hides before placing them in the
vegetable tan solution.
66
Dated this 8th day of November 1894
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.
Improvements in Tanning.
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 Friedrich Kornacher Technical Expert
and Journalist of Frankfort-on-the-Main and the Firm of Diesel & Weise of
Poessneck Manufacturers both in the Empire of Germany) and in what manner
the same is to be performed to be particularly described and ascertained in and
by the following statement:-
The object of this invention is to accelerate the manufacture of thoroughly
tanned leather, and it mainly consists in submitting skins or hides, before they are
steeped in the actual tanning solution to a preliminary treatment calculated to
work the skins or hides into a state of readiness for the subsequent tanning
process which may be then fully carried out within a very small space of time say
a few hours.
The preliminary treatment referred to partly consists in what is termed "mineral
tanning." Attempts have already been made to subject skins or hides to the action
of minerals before treating them with tan and the product obtained by this process:
was known as "half-tanned" leather, which, however, in the opinion of specialists
was deficient in quality (see the Vienna periodical "Die Weissgerberei" of the
year 1877, p. 298) and consequently soon disappeared from the market.
Now the leather obtained by the improved process according to this invention is
not half-tanned but completely tanned leather and does not in any way differ from
leather tanned by any of the ordinary known processes. The improved process
does not merely replace the so-called "mineral" tanning in a partial or superficial
manner, but is adapted thoroughly and completely to supersede mineral tauning, so
that no vestiges thereof remain behind or are traceable in the leather obtained as
a final product.
This result is attained by several manipulations which have some connection
with mineral tanning. The following is a description of the process carried out as
a whole according to this invention.
.
The hides or skins, prepared substantially in the manner practised hitherto but
if desired somewhat more limed and "oozed" and very carefully cleansed, are first
tinctured with a weak acidulated tanning decoction cr solution. The acidulation is

page_text: effected by means of tanning extract which has become acid by fermentation.
This acid extract is added to the tanning extract in the proportion of 10 or 16 parts
of acid extraet to 100 parts of ordinary extract. The object of the operation is
partly to enable the grain of the hides or skins more effectually to resist subsequent
reactions, and partly, to remove the particles of lime which would otherwise remain
behind in the hides or skins and interfere with the operations which are to follow.
The skins or hides thus tinctured and thoroughly washed are then treated by the
well known mineral process and after undergoing the treatment with the accessory
operations involved they are again slightly washed.
After this process the hides or skins in place of being immediately submitted to
the action of tan as bas been usual hitherto are first treated in a preliminary
operation which is of the greatest importance and absolutely necessary if
thoroughly tanned leather is to be obtained. To this end, the hides or skins after
undergoing the mineral treatment are lightly washed, dried, pared or split, and, if
necessary, stretched, or otherwise dressed or prepared, according to the nature of
the leather to be produced.
By this and the subsequent operations, the skin or hide is opened or made porous
and capable of absorption, to such an extent that the vegetable tanning process,
which is now to follow, may be performed completely in about as many hours, as
has taken months hitherto to complete while at the same time any tangible or
appreciable trace of the previous mineral tanning is entirely done away with. The
paring, splitting, or other dressing of the leather may, if preferred, be proceeded
with in the course of the tanning process itself, in which case these operations are
performed after the fresh. tanning operation has been started the skin being once
more dried for the purpose. Heavy skins or hides may after undergoing the first
stage of tanning be dried, pared, or split and they are preferably-tanned in a vat
which is so arranged that the said skins or hides-may be tightly stretched in frames
before being steeped in the tan.
As a strong tanning solution or ooze is employed at the very outset of the
process, it is advisable to rub fat or the like into the grain of the skin before it is
placed in the tanning solution. By such means the delicate layer or film which
forms the grain is protected from too energetic an action of the solution and
prevented from becoming hard and liable to split or crack; while at the same time,
in consequence of the fat or the like which gradually issues from the skin being
transformed into a delicate substance of the nature of an emulsion, the absorption
of the tan by the skin instead of being delayed is very materially promoted or
expedited.
Another essential condition on which the rapid and thorough completion of the
tanning depends is that the tanning solution employed should be slightly acidulated
whereby the skin is made to swell and its pores are opened so that it may more
readily absorb the tanning liquid.
The skin prepared in the manner described is now placed in the acidulated tanning
solution which should be of a density or strength of 3° or 4° Baumé or not much
below that and which is heated to from 30 degrees to 50 degrees Centigrade. While
in this solution the skins or hides are constantly stirred for which purpose a rotary
drum should in preference be used. In a short time after .commencing the opera-
tion, it will be found that the solution of tan has become saturated with the
mineral salts which have been expelled or eliminated from the skins or hides and
the solution must then be at once renewed. This renewal of the tanning solution
may be repeated several times until it is found that the liquid after the skins or
hides have been treated therein for a considerable space of time no longer contains
an appreciable proportion of mineral salts or kindred matter.
The tanning takes place in any suitable apparatus such as a fulling tank or vat
or the like, in which by means of any suitable arrangement the tanning solution is
maintained at the desired temperature and which should enable the liquid to be
readily discharged and renewed. The admission of fresh supplies of tanning
liquid is preferably effected by means of a pipe connected with an extraction

page_text: battery consisting of a series of vessels in which the bark is boiled with water for
extracting therefrom the tanning agent. The said pipe extends into the vat or th
like through the hollow shaft or trunnion of the latter and in this manner the skin;
may be fed with fresh tanning liquid during the rotation of the vat (which may be
cylindrical) whereby tanning is also assisted.
The vegetable tanning material employed is as usual, in the condition of an
aqueous solution.
Its composition depends on the nature of the hides or skin:
which are to be tanned and the purposes for which the leather is required whether
of a finer or coarser quality such as for example either for the manufacture of
boots and shoes or for saddle and harness making purposes indeed the tanning
compound may vary in a manner corresponding to the variations involved in the
usual practice for similar purposes.
By the process berein described, comparatively light hides and skins may be.
thoroughly tanned in a few hours, and the heavier sorts in one or more days, and
the leather obtained in this manner does not differ, either in appearance, in quality,
or in weight from the leather tanned by the long and tedious tanning methods
hitherto in use.
The treatment of the hides or skins by mineral salts does not constitute the
main object of the process, but is merely employed in conjunction with the other
manipulations hereinbefore described, for opening the pores of the skin or hide,
while all traces of such mineral treatment are entirely obliterated in the sub-
sequent phases of the process. Such mineral treatment may if preferred be replaced.
by other operations capable of serving the purpose for which the mineral salts are
employed vizt. that of rendering porous the hides or skins under treatment, provided
that the agents employed in carrying out such operation may subsequently be
eliminated from the hides or skins by the action of the heated tanning solution or
liquid. Other means which will serve also this purpose are known under the
names of "soap-tanning," "glycerine-tanning" and "fat-tanning." When one of
these said means is employed as a substitute for the "mineral-tanning" the
remaining portion of the process remains unaltered, except that, where the fatty
method is used it is of course unnecessary to grease the skins or hides before
placing them in the vegetable tan solution.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is :-
A process for the rapid and thorough tanning of hides or skins the said process
mainly consisting in subjecting the hides or skins after they have been washed or
cleansed and it necessary "tinctured" by means of a weak acidulated tan-solution
to treatment by the mineral process (or its equivalent as herein before explained)
then to washing, paring splitting and drying (and also greasing the grain if desired)
and then to tanning by means of acidulated vegetable tanning liquid, continuously
agitating or stirring during the operation; the said liquid being heated and during
the whole of the tanning process, maintained in a state of concentration of from
3° to 4° Baume or thereabouts and the liquid being renewed from time to time
with a view to the complete removal of the matter due to the preliminary treat-
ment by mineral tanning (or its equivalent) all substantially as hereinbefore
explained.
Dated this 24th day of July 1895.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents..