AN IMPROVED METHOD OF AND APPARATUS FOR TANNING AND OTHERWISE TREATING HIDES AND SKINS
Year: 1873

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane,
in the County of Middlesex, Patent Agent, for the Invention of
"AN IMPROVED METHOD OF AND APPARATUS FOR TANNING AND OTHERWISE
TREATING HIDES AND SKINS."-A communication from abroad by
Madame Malvina Frédérique Maric Schmidt-Ramspacher, of Paris,
France.
PROVISIONAL SPECIFICATION left. by the said Alexander Melville
Clark at the Office of the Commissioners of Patents, with his
Petition, on the 21st June 1873.
I, ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, do hereby declare the nature of
the said Invention for "AN IMPROVED METHOD OF AND APPARATUS FOR
TANNING AND OTHERWISE TREATING HIDES AND SKINS," to be as follows:-
The improved tanning process of this Invention is based on the
employment of an apparatus by means of which hides and skins are
impregnated with any suitable tanning liquors. This apparatus is com-
posed of a casing A, A, Figure 1, of square or rectangular form, made

page_text: perfectly tight and of materials not liable to be acted on by the tanning
liquors. At the centre T is a pipe Q having a tap R, and made funnel
mouthed at O. The casing A has a false bottom with apertures K, on
which is a filtering surface M. Pipe Q communicates with a reservoir
in which a vacuum is produced by any suitable means. The apparatus
is placed horizontally with the tap R shut when the ooze is poured
in until the filtering surface M is slightly covered, the latter having been
previously covered with some fabric. This being done the skin after it
has been washed is spread on the covered filtering surface as flat as
possible, which may be done without difficulty owing to its pliable con-
dition. After being thus spread out a fatty mastic is run around the
edges of the skin and the sides of the apparatus, any cracks or fissures in
the latter being also filled up with the mastic. By this means the tanning
juices are prevented from passing through the filter and are forced to
penetrate the pores of the skin.
The fabric above mentioned as covering the filtering surface is
employed to prevent the adhesion of the mastic thereto, and facilitate
its removal after each operation. The whole being thus arranged the
casing is filled with the liquor to be employed and tap R is opened to
establish communication with the exhausted receiver, and as the pressure
diminishes beneath the skin the liquor covering the same becomes drawn
into the pores, the tanning principle of the liquor combining with the
animal matter with which it is brought in contact.
It is important that the injection should be operated in an intermittent
manner, that is to say, it should be momentarily interrupted, and that
the liquor should be caused to act on each side of the skin alternately.
A constant filtration is unnecessary and even prejudicial as the great
quantity of liquor uselessly traversing the pores of the skin tends to
corrode its substance and render it brittle. By operating also on both
surfaces alternately both the grain and flesh sides relieve one another,
and they are not liable to be overtanned by the prolonged action of the
liquors. Thus when the flesh side has been operated on for some time
the skin is withdrawn and steeped in a tank containing a liquor of
rather stronger quality, other skins being meanwhile treated in the
apparatus. The first skin is then replaced in the apparatus to be
- impregnated on the grain side, after which it is again put into the vat,:,
and so on, until perfectly tanned. It is necessary to brush now and then

page_text: from the surfaces of the hides a mucilaginous substance which is
deposited thereon and forms a coat, which after a few days obstructs the
introduction of the liquor.
It is preferable to previously macerate the skins for some days in a
weak tanning liquor, the strength of which is gradually increased. By
this means a more soft and flexible grain is obtained, as the weak liquor
contains more extractive than tannin.
The lime which notwithstanding the washings remains in the skins,
forms with the tannin an almost insoluble calcareous tannate, which
deprives the hides of their suppleness and renders them dry and brittle.
In order to avoid this and obtain leather having great suppleness from
skins unhaired by means of lime I fix them in the machine and impregnate
them with a weak solution of glucose or other saccharine matter; the
sugar combines with the lime and forms a saccharate of lime, very
soluble in water. When the whole of the lime is thus transformed I
remove the saccharine liquid and filter pure water through them, which
dissolves and carrics off the saccharate of lime, which is thus effectually
removed from the skins.
The machine employed for tanning may thus also serve for other
purposes, according as it is desired to extract from the skins or hides
different substances; or, on the other hand, as it may be desired to
impregnate therewith certain matters in order to augment their weight
to render them supple, impermeable, or impart any other property. Thus
when I employ as tanning liquor the residues from distilleries, known as
essential or empyreumatic oils, an excellent leather is obtained, possessing
all the properties of the best Russia leather.
If instead of using these oils for tanning I inject tanned hides there-
with they are rendered absolutely impermeable.
The mastic which I generally use is a simple mixture of tallow and
arcanson melted together, but I may also use caoutchouc, the fat lute of
chemists, gutta percha melted or dissolved, tars, fatty, gummy, or
resinous bodies, plaster, or other luting.
To prevent the alteration of the ooze I preserve it in vats covered with
a layer of mastic, and each time that it has been used I filter it through
pulverized pumicestone impregnated with pyroligneous acid, creosote,

page_text: phenic acid, or other antiseptic. Instead of pumicestone pounded char-
coal or other porous matter may be employed.
The object of this filtration is to remove or destroy all the germs' of
fermentation often found in the liquors, and it is even advisable to filter
the water used for the extraction of the tannin principles. When the
filter needs revivifying the pumicestone is calcined and again impregnated
with the antiseptic liquor.
Another good precaution is to pass the ooze over fresh bark each time
that it has been purified by the filter.
T
To avoid the employment of a machine to produce the vacuum the
following modification of the apparatus may be made :-The cock R is
placed at the lower extremity of the pipe Q and should dip a short
distance into the ooze or liquor contained in the uncovered vat; then on
opening, cock R the column of liquid tends to run off, and produces on
the skin a suction which draws up the tannin liquor. The strength of
this suction varies according to the vertical distance (which should not
exceed 32 feet) between the filter and the surface of the liquid into
which the pipe dips. The length and inclination of this tube which
thus forms a barometric column having no effect.
+
Notwithstanding the interposition of the mastic and every possible 2
precaution some leakages are to be expected, to guard against which
pipe Q should be of such a size that the action will be slow and the
suction therefore rather less although it will not cease to act on the skin.
A glass tube may be attached to pipe Q composed of several lengths, if
necessary, with india-rubber unions, by which means the speed with
which the liquid runs off can be readily ascertained.
Instead of employing the action of exhaustion to impregnate the skin
I may employ pressure on the liquor, covering the skin with the same
result.

page_text: ་
t
SPECIFICATION in pursuance of the conditions of the Letters Patent
filed by the said Alexander Melville Clark in the Great Seal Patent
Office on the 19th December 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letter's
Patent, bearing date the Twenty-first day of June, in the year of our Lord
One thousand eight hundred and seventy-three, in the thirty-seventh
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Alexander Melville Clark, Her special licence
that I, the said Alexander Melville Clark, my executors, administrators,
and assigns, or such others as I, the said Alexander Melville Clark,
my executors, administrators, and assigns, should at any time agrée
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, the Channel Islands, and Isle of Man, an Invention for
"AN IMPROVED METHOD OF AND APPARATUS FOR TANNING AND OTHERWISE TREATING
HIDES AND SKINS," a communication to me from abroad by Madame
Malvina Frédérique Marie Schmidt-Ramspacher, of Paris, France, upon
the condition (amongst others) that I, the said Alexander Melville
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 ascertain 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 Alexander Melville Clark, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement, reference being had to the accompanying
Sheets of Drawings and to the letters and figures marked thereon (that is
to say):-
:.)
The improved tanning process of this Invention is based on the
employment of an apparatus by means of which the tanning or other

page_text: liquors are caused to penetrate the hides or skins by infiltration. Figure 1
of the accompanying Drawing shows a plan of the apparatus; Figure 2
an elevation, and Figure 3 a section of same on line c, c, Figure 1. This
apparatus is composed of a shallow tray or case A, A, Figure 1, placed
horizontally, of square or rectangular form, made perfectly tight and of
materials not liable to be acted on by the tanning liquor. At the
'centre T is a pipe Q having a tap R and made funnel mouthed at O.
The casing A has a false bottom with apertures K on which is a
porous surface M.
Pipe communicates with an exhausted receiver,
the vacuum being produced by any suitable means. The apparatus
being thus arranged with the tap R shut the ooze is poured in until
the surface M (upon which some woven fabric or covering has been
previously laid) is covered. This being done the skin after it has been
washed is spread on the covered surface as smoothly as possible, which
may be done without difficulty owing to its pliable condition. After
being thus spread out a fatty mastic is run around the edges of the skin
and the sides of the apparatus, any cracks or fissures in the skin
being also filled up with the mastic. By this means the tanning
liquor is prevented from escaping without penetrating the pores of
the skin.
The covering or fabric above mentioned as being placed on the
surface M beneath the skin is employed to prevent the adhesion of the
mastic to the said porous surface and facilitate the removal of the skin
after each operation. The whole being thus prepared the tray is filled
with the liquor to be employed, and tap R is opened to establish com-
munication with the exhausted receiver, and as the atmospheric pressure
is removed beneath the skin the pressure on the liquor covering the
skin forces it through the pores where the tanning principle of the
liquor combines with the animal matter with which it is brought in
contact.
It is important that the infiltration should be intermittent, that is to
say, should be interrupted and that the liquor should be caused to act
on each side of the skin alternately. This intermittent action is
necessary because the liquor would otherwise continue to pass through
the skin without any sensible diminution of its strength, whereas when
once the liquor has permeated the skin time should be allowed for
the chemical changes which it is intended to produce, hence a constant
infiltration would be prejudicial, as the great quantity of liquor uselessly

page_text: .
-
traversing the pores of the skin would tend to corrode its substance
and render it brittle. By operating also on both surfaces alternately
both the grain and flesh sides of the skin relieve one another, and they
are not liable to be overtanned by the prolonged action of the liquors.
Thus when the flesh side has been operated on for some time the skin is
withdrawn and steeped in a tank containing a liquor of rather stronger
quality, other skins being meanwhile treated in the apparatus. The first
skin is then replaced in the apparatus for the liquor to infiltrate it on
the grain side, after which it is again put in the vat and the operation
repeated until it is perfectly tanned. It is necessary to brush now and
then from the surfaces of the hides a mucilaginous substance which is
deposited thereon and forms a coat which after a few days obstructs the
introduction of the liquor..
It is preferable to previously maccrate the skins for some days in a
weak tanning liquor the strength of which is gradually increased.
By this means a softer, and more flexible grain is obtained, as the weak
liquor containing more extractive than tannin the leather is enabled
to absorb that proportion of the former which is necessary to render it
supple.
The lime which, notwithstanding repeated washing remains in skins
forms with the tannin an almost insoluble calcareous tannate, which
deprives leather of its suppleness and renders it dry and brittle. In
order to avoid this and obtain leather having great suppleness from
skins unhaired by means of lime I fix them in the apparatus and
impregnate them with a weak solution of glucose or other saccharinė
matter, whereupon the sugar combines with the lime and forms a
saccharate of lime very soluble in water. When the whole of the lime
is thus transformed I remove the saccharine liquid and substitute purė
water, which percolates the skins and dissolves and effectually removes
the saccharate of lime.
The apparatus employed for tanning may thus also serve for other
purposes, according as it is desired to extract from the skins or hides
different substances, or on the other hand as it may be desired to
impregnate them with certain matters in order to augment their weight
to render them supple, impermeable, or impart any other property:
Thus when I employ as tanning liquor the residues from distilleries
known as essential or empyreumatic oils, an excellent leather is obtained
possessing all the properties of the best Russia leather.

page_text: "
:
If instead of using. these oils for..tanning I impregnate tanned hides.
therewith they are rendered absolutely impermeable.
The mastic which I generally use is a simple mixture of tallow and
colophony melted together, but I may also use caoutchouc, the fat lute
of chemists, gutta percha melted or dissolved, tars, fatty, gummy, or
resinous bodies, plaster, or other luting,
To prevent alteration of the ooze I preserve it in vats covered with 'a
layer of mastic, and each time that it has been used I filter it throughì
pulverized pumicestone impregnated with pyroligneous acid, creosote,
phenic acid, or other antiseptic. Instead of pumicestone pounded
charcoal or other porous matter may be employed! we hop
1
The object of this filtration is to remove or destroy all the germs of
fermentation often found in the liquors, and it is even advisable to
filter the water used for the extraction of the tanning principles. When
the filter needs revivifying the pumicestone is calcined and again
impregnated with the antiseptic liquor.
1
• T
Another good precaution is to pass the ooze over fresh bark cach time
that it has been purified by the filter.
migo chiub
177
"
domi!
(11 T
P
(
To avoid, the employment of a machine to produce the vacuum, the
following modification of the apparatus may be made:-The cock R is
placed at the lower extremity of the pipe Q and should dip a short
distance into the ooze or liquor contained in an uncovered vat. Then
on opening cock R the column of liquid tends to run off and produces
a suction which draws the tanning liquor through the skin. The a
force of this suction, varies according to the vertical distance (which
should not exceed 32 feet) between the hide or skin and the surface of
the liquid into which the pipe dips, the actual length and inclination
of the pipe (which thus forms a barometric column) having no effect.
"
".
་་་་
Notwithstanding the interposition of the mastic and every, possible a
precaution leakages are to be expected, to guard, against which pipe Q
should be of such a size that the action will be slow and the suction
therefore rather less, although it will not cease to act on the skin.. A ;
glass tube may be attached to pipe Q composed of several lengths, if
necessary, with india-rubber unions, by which means the speed with 3
which the liquid runs off can be readily ascertained. Nodi na glikog
t

page_text: Instead of employing the action of exhaustion to infiltrate the liquor
through the skin I may employ hydrostatic or other pressure on the
liquid covering the skin with the same result. The only difference will
be in the construction of the apparatus which will require greater
strength, and will therefore be more expensive.
It will be evident that by making the receptacle of sufficient height
several diaphragms may be arranged therein one above the other to
support several skins.
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 in part recited Letters Patent is, a tray or
casing with inner perforated false bottom supporting a porous surface
covered with some woven fabric, on which the skin to be tanned is
spread and luted to the edges of the casing with mastic, the bottom of
said casing communicating by means of a pipe with an exhausted
receiver or with any apparatus for producing a vacuum and consequently
a pressure upon the ooze or liquor whereby it is caused to penetrate the
skin by infiltration (or the pressure may be applied directly upon the
skin) all as herein specified.
In witness whereof, I, the said Alexander Melville Clark, have
hereunto set my hand and scal, this Eighteenth day of
December, in the year of our Lord One thousand eight hundred
and seventy-three.