Iм- PROVEMENTS IN TANNING HIDES, AND IN APPARATUS EMPLOYED THEREIN
Year: 1858

page_text: LETTERS PATENT to William Clark, of 53, Chancery Lane, in the County
of Middlesex, Engineer & Patent Agent, for the Invention of "Iм-
PROVEMENTS IN TANNING HIDES, AND IN APPARATUS EMPLOYED THEREIN."-
ination déning Louie Adelaho Tavio
Sealed the 1st April 1859, and dated the 14th October 1858.
PROVISIONAL SPECIFICATION left by the said William Clark at the
Office of the Commissioners of Patents, with his Petition, on the 14th
October 1858.
I, WILLIAM CLARK, of 53, Chancery Lane, in the County of Middlesex,
Engineer & Patent Agent, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN TANNING HIDES, AND IN APPARATUS EMPLOYED THEREIN,"
to be as follows:-
This Invention relates to new processes for tanning hides rapidly, which
consist in causing the tanning liquid to be filtered through the hide, and also
in improved means for effecting that object; 1st, by augmenting the pressure
of the tanning liquid on that side of the hide at which it is introduced;
2ndly, by diminishing the pressure of the atmosphere on that side of the hide
at which the tanning liquid leaves the hide. For this purpose two methods are

page_text: employed; 1st, effecting the tanning operation by the simple pressure of
the liquid which is filtered through the hide from one side; 2ndly, by the
pressure of the liquid which is filtered through from one side of the hide, and
by a vacuum produced on the other side of the hide.
First Process. After the hide has been deprived of the hair by the ordinary
processes, and it has undergone the preparation which usually procedes the
placing it in the tan pit in ordinary tan yards, it is folded, placing the two
surfaces in contact and the edges together, it is then placed between the two
parts of a double jointed frame of wood or copper, the parts of the frame are
then forcibly tightened by means of pincers, bolts, or thumbscrews. The
whole is then suspended, so that the back of the skin shall be undermost, by
means of rods or chains hooked to different parts of the frame, and supported
by one or two horizontal cross bars of wood. A space is left at a point of the
frame between any two corresponding arms for the passage of a pipe, through
which to introduce into the hide (which is formed into a completely closed
pocket or sack) a solution of tannic acid or other substance suitable for
tanning hides. This solution suitably concentrated is introduced into the
hide at a pressure of about one atmosphere, either by forcing by means of a
pump, or by pouring it in from a reservoir placed at about twelve or fifteen
yards above the floor of the place in which the tanning is effected. The
solution may also be introduced into the hide when in the form of a closed
packet by a hole made in the hide at any part of its surface, but preferably at
one of its extremities near the head or the tail. The edges of this hole are
held between two plates of copper, which are clipped together by means of
thumbscrews, and which plates are fixed at their centre to the pipe for the
introduction of the tanning substance. The pipe is furnished at its lower
extremity where it is in contact with the hide, 1st, with a stop-cock, which
serves to open or close the communication between the pocket formed by the
hide, and the reservoir above filled with tannic acid; and, 2ndly, with a knee
pipe fitted between the hide and the first stop-cock, which is also supplied
with a stop-cock. During the tanning operation the stop-cock in the knee
pipe is closed, and that of the principal pipe is opened, but when it is required
to empty the hide after the operation, and also during the operation for
renewing the solution with which the hide is filled, the stop-cock in the
principal pipe is closed and the hole in the knee pipe opened. The hole for
the introduction of the solution should be made in the lowest part of the hide,
so as to completely empty it when necessary. The hide being suspended as
above described, and having no part in contact with surrounding bodies, the

page_text: stop-cock in the principal pipe is partially opened, so as to slowly fill the sack
formed by the hide, and when filled it is completely opened. The liquid now
passes through the hide in the same manner as through a filter, and in
proportion as the liquid enters the hide, the tannin, which is held in solution
in it, combines with the elements of which the hide consists, and the tanning
is effected so rapidly as to be complete in about thirty-six hours, or forty-eight
hours at most.
For quickening the tanning operation the hide should be completely
emptied about twelve or fifteen hours from the commencement of the opera-
tion, to be refilled with a more concentrated solution than the first. This is
rendered easy by putting the tube of introduction in communication by means
of stop-cocks with upper reservoirs containing solutions more or less concen-
trated as determined by experience. A great number of hides may be
arranged in one apartment by placing them perpendicularly to the walls.
The liquid which escapes from the hides falls into troughs placed under each,
and runs from them by means of channels into a reservoir, whence it is removed
for the purpose of being concentrated by evaporation to the degree suitable to
be used again in tanning; when thus concentrated it is transferred to the
upper reservoirs by means of a force pump, adding to it the necessary solution
for replacing that used in the previons operation.
By treating any hide in the manner above described, the tanning operation,
properly so called, is completed in about forty-eight hours at most; the hide is
then emptied and the frame separated at the parts by which the edges of the
hide are held, and there only remains to dry and prepare it as is usual after the
operation of tanning for commercial uses. The time necessary for the tanning
may be reduced one half in the process above described, if during the opera-
tion each hide is enclosed in a case where a partial vacuum is obtained; but
if a vacuum and pressure is required simultaneously, it is preferable to make
use of the process herein-after described as the 2nd process.
Two hides may likewise be tanned together by gripping the corresponding
edges between the parts of the jointed frame, consisting, as before described,
of arms of about ten inches in length; but this arrangement presents incon-
veniences, inasmuch as the hides when thus treated together, not being
exactly alike, are not both tanned completely at the same time, and conse-
quently the tanning of each hide could not be effected so exactly as it may be
wished, which is the case when the hides are treated separately.
2nd Process. In the first place, the form of the hide to be tanned is
modified by cutting the edges according to a polygonal pattern previously

page_text: prepared. The parts of the hide thus cut off are those of the least value, and
which are utilised so as to obviate any loss or waste of the tanned leather.
The bide is then deprived of the hair and prepared as is usual before being placed
in the tan pit of ordinary tan yards; it is then placed on a grating formed of
straight parallel bars of wood or copper, which grating is of a similar form to
that of the pattern used for modifying the shape of the .hide, but is of less
area than the pattern, so that the trimmed edges of the hide may overlap that
of the grating about one inch and a half all round; this inch and a half of hide
rests on a framing of copper, which is independent of the grating & furnished
with small copper points, which penetrate the edges of the hide, and servo to
keep it in position on the grating. This grating rests on a large vat of copper,
of enamelled cast iron, or of sheet iron glazed, having an orifice at the centre,
to which a copper tube is fitted, furnished with a stop-cock, which tube is
extended to an air pump, by means of which a vacuum is obtained under the
hide. The bars of the grating are widened at their lower part, so that a
vacuum may be obtained in all the compartments formed by these bars, and
for allowing the liquid to run freely, which passes through the hide during
the operation.
The stop-cock placed in the vat which carries the gratings is so arranged
as to be able at will to put the interior of the vat in communication with the
air pump, at the same time cutting off the exterior air or to cut off com-
munication with the air pump, and at the same time to put it in communication
with the atmosphere. The hide being spread on the grating to which it is
held by the points, the edges of the frame before-mentioned are covered by a
vat similar to the one which supports the grating, but placed in a reverse
position, and the edges of which are superposed on the frame, to which the
edges of the hide aro secured by means of plates of copper. The hide is
then held at the edges to the extent of about one inch and a half in
width between those plates and the frame of the grating, which are then
forcibly pinched together by means of thumbscrews or other suitable means.
The reversed vat which covers the hide is furnished at the centre with an
orifice, through which a pipe passes furnished with a stop-cock communicating
with reservoirs filled with tannic acid placed about twelve or fifteen yards
above the apparatus.
For the purpose of leaving the least possible passage for the air when pro-
ceeding to obtain a vacuum under the hide, care is taken to place sheets of
gutta percha or india-rubber between the edges of the lower vat and the frame
which surrounds the grating; sheets of gutta percba are also .interposed

page_text: between one copper plates covering the cages of the ages of the
upper vat.
The whole being arranged as above described, the stop-cock of the pipe for
the admission of the tannin is opened, the solution then fills the upper vat, and
is filtered through the hide, leaving behind the greater part of the tannin
which it contained, and which combines with the elements composing the hido
as in the former process, for the purpose of hastening the passage of the liquid
through the hide, and consequently the tanning operation; the stop-cock
placed under the lower vat is opened, and the air pump worked so as to create
a partial vacuum under the hide in the spaces which exist between the bars of
the grating which carry it. The liquid which passes through the hide after
parting with the greater part of the tannin it contained runs through the pipe
of the air pump to a closed reservoir placed at any point of its length in a
downward direction from the apparatus which contains the hide, from which it
is withdrawn by a stop-cock after the operation, to be concentrated to the
required degree to be again made use of in subsequent operations, as mentioned
in the description of the first process. When the hide has been submitted for
five or six hours at most to the double action of a vacuum below and pressure
from above, the stop-cock for the introduction of the tannin is closed, and the
air pump continued to be worked for about half an hour, so as to force through
the hide the liquid which is still contained in the upper vat so as to empty it
completely. Communication is then cut off between the lower pipe and the
air pump by means of a peculiar stop-cock for that purpose, at the same time
the interior of the apparatus containing the hide is placed in communication
with the exterior atmosphere.
This being done, the apparatus is disconnected and the upper vat removed,
the hide is then unhooked at one end, at it is lifted up for the purpose of
slightly displacing the grating, which supports it in such manner that the parts
which first rested on the bars of the grating may coincide with the spaces
existing between them; the hide is then replaced in its former position, as also
the upper vat, and the operation is recommenced as above detailed, opening
successively the cock for the admission of the tannin, and the one com-
municating from the apparatus to the air pump.
The displacement of the grating in the second stage of the operation is
intended to allow the tannin to pass through those parts of the hide which
previously rested on the bars of the grating, and so to insure the perfect tanning
of the leather.
After the hide has been thus treated by means of a vacuum, and also by

page_text: pressure at two different intervals of time, about six hours or more each, the
tanning, properly so called, is completed, the hide may then be dried, and
afterwards applied to commercial purposes.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Clark in the Great Seal Patent Office on the
9th April 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
CLARK, of 53, Chancery Lane, in the County of Middlesex, Engineer &
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourteenth day of October, in the year of our Lord
One thousand eight hundred and fifty-eight, in the twenty-second year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said William Clark, Her special licence that I, the said William Clark, my
executors, administrators, and assigns, or such others as J, the said William
Clark, my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland, tho
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
TANNING HIDES, AND IN APPARATUS EMPLOYED THEREIN," a communication,
upon the condition (amongst others) that 1, the said William Clark,
my executors or administrators, by an instrument in writing under my, or
their, or one of their hands and seals, should particularly describe and ascer-
tain the nature of the said Invention, and in what manner the same was
to be performed, and cause the same to be filed in the Great Seal Patent
Office within six calendar months next and immediately after the date of the
said Letters Patent.
NOW KNOW YE, that I, the said William Clark, do hereby declare the
nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, reference being had to the Sheet of Drawings hereunto annexed,
and to the letters and figures marked thereon (that is to say) :-
:-
This Invention relates to certain new processes for tanning hides rapidly,
and consists in causing the tanning liquid to penetrate through the fibres of s

page_text: the skin, first, by applying the pressure of a column of tanning liquid;
secondly, by means of a vacuum, which two processes can be employed either
jointly or separately.
First Process. Tanning by application of the pressure of the tanning liquid.
Figs. 3 and 4 represent front and side views of the apparatus employed.
a shows the vat, placed at a height depending upon the pressure desired to be
obtained, which vat contains the tanning liquid; b, double frame, consisting of
parts binged together, and capable of being connected by means of screws or
any other suitable means; c, the skin or hide stripped of its hair, the skirts or
edges of which after being placed together are fastened tightly between the
several parts of the frame so as to form a sort of bag; d, tubes provided with
stop-cocks for conveying the liquid from the vat a into the pocket or sack
formed by the skin. With such an arrangement, and the vat a being raised
about thirty-two feet, for instance, above the hide or skin, the tanning liquid
descends from this reservoir, and filters or penetrates through the hide or skin
under the pressure of one atmosphere, and the said skin or hide will thereby
be tanned. The force pump e is intended to force the tanning liquid through
the pipe into the pocket or sack formed by the skin when there is no vat
placed at the upper part.
Second Process. That is to say, when tanning by pressure of the liquid
and by a vacuum. Figs. 1 and 2 represent the front and side views of the
apparatus employed in such case. d is the tube conveying the tanning liquid
from a vat placed above; g and h, upper and lower vats; c shows the hide or
skin stripped of its hair, and forming a diaphragm between the two vats,
its skirts or edges being fastened between the two horizontal flanches of
the vats, and suitably shaped for the purpose; i is a grating movable by
means of a handle, and supporting the stretched skin; j, exhaust pump for
exhausting the air, and communicating with the box or vat h by a pipe k.
All the parts being arranged as shown in the Drawings, the air is then
exhausted or drawn from the vat h by means of the aforesaid pump. The
liquid running from the upper vat will filter or penetrate through the skin at
a rate according to the difference of pressure, and thereby effect the tanning
of the hide or skin. After the filtering process has been in action for a certain
time, the supporting grating i is moved in order that the liquid may act on
those places on which its action has been prevented by the bars of the
grating.
Third Process. For tanning by means of the vacuum alone. Fig. 5 repre-
sents a vertical section of the apparatus employed. h, h, shows the vat, the

page_text: lower part of which is raised to more than thirty-four feet above the surface of
the ground; c, the hide or skin, is stretched on the horizontal flanch of the
vat h, it being suitably shaped for the purpose; i, i, the movable grating
supporting the stretched hide or skin; 1, reservoir placed on the ground, and
communicating with the vat h through a pipe m, provided with a stop-cock;
n, guage indicating the height of the liquid, which guage or liquid is placed
-above the ground at the height of the barometrical liquid.
All the parts being thus disposed, and as shown, and supposing the apparatus
filled with the tanning liquid, if the cock of pipe m is opened, the said liquid
will run down through the said pipe to the barometrical height, and cause a
vacuum in the vat h, h, so that a new amount of tanning liquid poured on the
upper part of the hide or skin c will filter through it at a rate in proportion to
the difference of pressure, and flow out constantly through the pipe m in such
manner that the vacuum is thereby self-maintaining.
The grate can bo moved like that before mentioned, and for the same
purpose. If the vat h be placed on the ground, then the reservoir / must be
placed in a shaft dug to the depth of upwards of thirty-four feet. Instead of a
complete vacuum, a partial vacuum can be obtained by diminishing the height
of the tube m. For the construction of the apparatus no substances are
employed but such as cannot be attacked by the tanning matters.
By the application of the above processes two or more hides or skins can be
tanned at once. Fig. 6 represents an apparatus for similar purposes, but
admitting of a second vat. In using this apparatus the skin is secured by the
skirts or edges between the two flanches of the vat. In this Figure the same
letters stand for like parts in Fig. 5.
Having described the nature of the Invention, and the manner of performing
the same, I declare that what I claim as the Invention, to be protected by the
herein-before recited Letters Patent, is,-'
First, the tanning of hides or skins by forcing the tanning liquid to filter
or penetrate through the skin in proportion to the pressure due to a
corresponding height of liquid, as above described, and as represented at
Figs. 3 & 4.
Secondly, the tanning of hides or skins by causing the tanning liquid to
filter or penetrate through the skin in proportion to the pressure due to a
corresponding height of liquid, and also by a certain vacuum operated on the
opposite side of said skin, as aforesaid, and as represented at Figs. 1 and 2.
Thirdly, the tanning of hides or skins by causing the tanning liquid to
filter or penetrate through the skin in proportion to a certain vacuum

page_text: operated on the opposite side of said skin by means of apparatus producing
the vacuum by the column of fluid, as above described and as represented at
Figs. 4 & 5.
Fourthly and lastly, I claim the arrangement of the two first apparatus for
tanning by pressure alone, and by pressure and a vacuum combined.
In witness whereof, I, the said William Clark, have hereunto set my
band and seal, this Fifth day of April, in the year of our Lord One
thousand eight hundred and fifty-nine.
Witness,
W. G. E. SWINNOCK,
53, Chancery Lane.
W. CLARK. (L.S.)