IMPROVEMENTS. IN PREPARING FOR TANNING, AND IN TANNING HIDES AND SKINS
Year: 1856

page_text: LETTERS PATENT to Etienne Sterlingue, Manufacturer, of Paris, Town in
the French Empire, for the Invention of "IMPROVEMENTS. IN PREPARING
FOR TANNING, AND IN TANNING HIDES AND SKINS."
Sealed the 80th January 1857, and dated the 23rd August 1856.
PROVISIONAL SPECIFICATION left by the said Etienne Sterlingue at
the Office of the Commissioners of Patents, with his Petition, on the
28rd August 1856.-
I, ETIENNE STERLINGUE, Manufacturer, of Paris, Town in the French
Empire, do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN PREPARING FOR TANNING; AND IN TANNING HIDES AND' SKINS," to-be as
follows:-
My Invention consists in an improved treatment of skins and hides, in
order to remove the hair, &c. therefrom previously to their being tanned; in
tanning skins and hides without subjecting them to the preliminary treatment
with acids or acid baths, usually practised for the purpose of "raising" the
hides and skins and swelling the fibres; also in an improved method of
tanning, in which a single skin or hide is submitted separately to the action
of the 'tan; and in the arrangement and construction of tan pits.
I have ascertained that the action of acids on the skins tends to separate
the gelatine from the fatty matters contained therein, and thereby retard the

page_text: process of tanning. In my process of tanning, therefore, I take skins and
hides after the flesh and hair have been stripped off, and without preliminary
treatment I place them in direct contact with the ground bark or tan, and
the ooze, tan liquors, or tannic acid solutions. In preparing thick hides, such
as strong sole leather, after washing the hides, as usual, I proceed to loosen
the hair by steaming; but for this purpose, instead of suspending them in
drying stoves or smoke houses, I steam them in my improved tan pits, which
are made of wood, strengthened with iron hoops, and are shaped like the
frustum of a cone, being larger at bottom than at the mouth. The hides are
stretched on wooden frames, which are lowered into the pit, being guided in
their descent by ribs formed on the inside of the pit; the pit is then covered
over, and steam admitted from the bottom. The temperature should be
carefully regulated, for which purpose pipes or flues are carried from the
bottom to the outside of the pits at different heights. The hide is then
stretched on the frame or on a table, smoothed by hand or otherwise, to
remove defects and unevenness, and the desired shape, size, and thickness aro
given to it, which is facilitated by the flexibility of the gelatine. Each hide
is then placed singly in a shallow frame, and rolled on to a layer of tan
strewn therein, another layer of tan is placed on the top, and the frame
holding the hide and tan is lowered into the pit. Other frames, each con-
taining a single hide with two layers of tan are added, and when a sufficient
number of frames and hides have been placed in the pit it is closed, steam is
admitted through the double bottom, and the temperature of the pit raised to,
say, 60° Fahrenheit. The steam is shut off after a time, and ooze or tanning
liquors, or solutions of tannic acids, are poured in the pit until it is full. In
about a fortnight the tanning liquors may be drawn off, the pit opened, and
the hides withdrawn, removed from their frames, and piled in heaps in suitable
pits, in which the tannin not used up is allowed to drain off. The operation
is then repeated, but deeper frames are used, so that several hides may be
laid in one frame, a layer of tan between each hide. The frames are placed
in the pit and treated as before. This may be repeated for a third and fourth
time, if needful, each time, the operation lasting about a fortnight, the doses
of tannic acid being increased. The tan liquor that remains in the hides after
their removal from the pits, and which is drained off, as before stated, is
collected and pumped up into tanks from which the pits are supplied. The
tanning is now completed, and the hides have only to be dried and beaten.
For skins, such as those for upper leather, calf skin, &c., I treat them with
milk of lime, and wash them in a running stream, and, as usual, they are

page_text: then smoothened and worked up into shape by hand or otherwise. Each
single skin is then stretched on a separate frame between two layers of tan
and lowered into the pit, which, when a sufficient number of frames have
been placed in it, is covered over. Steam is admitted and shut off, and
tanning liquor or ooze poured in, all as described with reference to hard hides;
but in repeating the operation for this description of skins each skin should
be placed in a separate frame. Kids and sheep skins for gloves, &c., and all
skins that have to be grained, are washed in running water as usual, then
immersed and stirred about or "handled" in a weak bath of liquid, after
which they are laid in frames in alternate layers of skin and tan (the latter
being in sufficient quantity to completely tan the skin) and lowered into the
pit. They will be completely tanned in about a fortnight.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Etienne Sterlingue in the Great Seal Patent Office on the
23rd February 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ETIENNE.
STERLINGUE, Manufacturer, of Paris, Town in the French Empire, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-third day of August, in the year of our Lord
One thousand eight hundred and fifty-six, in the twentieth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Etienne Sterlingue, Her special licence that I, the said Etienne Sterlingue,
my executors, administrators, and assigns, or such others as I, the said
Etienne Sterlingue, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times there-
after 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 "IMPROVE-
MENTS IN PREPARING FOR TANNING, AND IN TANNING HIDES AND SKINS," upon the
condition (amongst others) that I, the said Etienne Sterlingue, 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

page_text: 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.
1.
NOW KNOW YE, that I, the said Etienne Sterlingue, do hereby declare
the nature of my 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 Drawings hereunto annexed, that, is
to say:
My, Invention consists in tanning bides and skins without subjecting. them
to the preliminary treatment with acids or acid baths, usually practised for the
purpose of "raising" the hides and skins, and swelling the fibres; also in,an.
improved treatment of skins and hides in order to loosen the hair, &c., thereon
previously to their being tanned; also in an improved method of tanning, in
which a single skin or hide is in the first instance submitted separately to the
action of the tan or bark, and in which steam is employed and tan liquors
let in, all as to be presently described; and the Invention also includes an
improved arrangement & construction of tan pits.
I have ascertained that the action of acids on skins tends to separate the
gelatine and fatty matters, and thereby retard the tanning. Now, in my
process, the skins and hides, after the flesh and hair have been stripped off,
and without any further preliminary treatment, are placed in direct contact
with the ground bark, tannin or tan, and the ooze, tan liquors, or tannic, acid
solutions, the process of "raising" or swelling with acids being thus wholly
dispensed with.
.In preparing thick hides and skins, such as for strong sole leathers, after
washing and cleansing the hides, as usual, I proceed to loosen the hair by
steaming;. but, for this purpose, instead of suspending them in drying stoves or
smoke houses, I steam them in my improved tan pits, in the manner to be
presently described. My improved tan pits are made of wood, strengthened
with iron hoops, and are of a conical shape, that is to say, shaped like the
frustum of a cone or a truncated cone, being larger at bottom than at the
mouth, but the sides are sloped very slightly. This conical shape is given to
the pits to render them the more solid. The hides are stretched. on circular
wooden frames, which are lowered into the pit, being guided in. their descent by
ribs or guide plates formed on the inside of the pit. These plates are required
to guide the frames, when lowered, on account of the conical shape. of the sides
of the pit; the pit is then covered over, and steam admitted.below..through a
perforated false bottom fitted in the pit. The temperature should be carefully
regulated, for which; purpose; pipes or flues are carried from the bottom to the

page_text: outside of the pit at different heights. The skins are subjected to the action
of steam for ten to fifteen hours. The frames are then hoisted out of the pit,
and the skins are ready to be unhaired and fleshed in the usual manner. The
hide or skin is then stretched on the frame or on a table, and smoothed by
hand or otherwise, in order to remove defects and unevenness, and to impart
to it the desired shape, size, and thickness, which is facilitated by the flexibility
of the gelatine. Each hide or skin is then placed singly in a shallower
frame, and rolled on to a layer or bed of bark, tannin, or tan strewn thereon,
and another bed of tan or bark is placed on the top, and the frame holding
the hide and tan is lowered into the pit. (I have found about 98 lbs. bark to
a hide weighing about 110 lbs. a fair proportion). Other frames, each con-
taining a single hide between two beds of tan, may then be lowered, and when
a sufficient number have been placed in the pit it is closed or covered over,
and steam admitted through the double bottom. The temperature of the pit
is, raised to say, 60° Fahrenheit; the steam is then shut off, and ooze,
tanning liquor, or infusions of tannic acids (weighing about 10 degrees of
the alcohometer) are poured into the pit until it is full. The temperature and
strength of the solutions may be tested at various depths through the flues or
pipes before referred to. In about a fortnight the tanning liquors may be
drawn off, the pit opened, and the hides or skins withdrawn, removed from
their frames, and piled up in heaps in suitable pits or receptacles, while the
waste tan that has not combined with the fibres of the skin is run off into
vats, and the tannin yet remaining is extracted from it. The operation is
then repeated, but deeper frames are used, so that several hides (say 5 or 6)
may be laid in one frame, a bed of tan or bark between each hide; these
frames may be about thrice as deep as the others. The frames are lowered
into the pit, which is covered over, and steam admitted as before, but so as
to be diffused sufficiently slowly as partially to condense, whereby the pores
of the skins are opened, and the tan bark is moistened and prepared to
readily yield its tannin to the infusion. When the temperature is about
60° Fahrenheit tannic acid infusions are poured into the pit (at about 8 of
the areometer). The skins are kept in the pit about a fortnight, when the
liquors are drawn off and the pit opened. The operation may be repeated
a third and a fourth time, if needfull, each time lasting about a fortnight, and
the doses of tannic acid being increased. The tan liquor that remains in the
hides after their removal from the pits, and which is drained off as before
stated, is collected in a common channel, and pumped up into tanks, in which
they may be heated with steam, and from which the pits are supplied. The
tanning is now completed, and the skins are ready to be dried and beaten.

page_text: Figure 1 of the annexed Drawings is an elevation, and Fig. 2 a plan, of
the improved pits employed in carrying the Invention into effect; Fig. 3 is a
sectional elevation; Fig. 4, plan in section. A, B, C, are the pits; B, B', are
the ribs or guide plates, which are broad or spread out at the base, and taper
off towards the top edge of the pit, the base being of the same length as that
of the difference between the top and bottom circumferences of the pit, their
inner edges thus forming the outlines of an imaginary prism described within
the pit, thereby guiding the frames in their descent down the conical sides of
the pit; C, C, are the frames for holding the skins or hides; they are formed
with a flange or rim round their edge, and are made of perforated boards, held
together by wooden stays or ribs D, D, at bottom; E, E, are rings or handles
by which to raise and lower the frames; D¹ is the false bottom of the pit,
under which steam is admitted through a pipe n, having a stop-cock r; E' are
pipes or flues communicating from the bottom of the pit to the outside at any
desired height, and through which a thermometer may be inserted to note the
state of the temperature, in order duly to regulate it. The hides when laid in
the frame to be steamed, in order to loosen the hair, before proceeding to tan
them, may be folded lengthwise, and piled up to the top rims. The frames
are lowered by a crane or other equivalent contrivance, the first frame resting
on the false bottom of the pit by its ledges D, D, the ledge of the next frame
resting on the top edge of the first frame, and so on. To admit the steam, the
tap is turned, and the steam passes through the pipe n and perforated false
bottom, becomes diffused throughout the pit, and condenses on the skins, the
waters of condensation being discharged through the false bottom and pipe m
into a channel M. The temperature of the pit is brought from about 77°
to 95°. During the operation of tanning, the strength of the solutions and
their temperature at various depths may be observed through the test tubes E.
The skins are left in the pits for about a fortnight, after which the tap m is
opened, and the whole of the liquid flows through into the channel M, and
thence into a tank. The channel M may serve for two rows of pits. The
frames for the first tanning may be about two or three inches deep, those for
the second tanning about eight inches. When the hides are subjected to the
second tanning, they are laid, as previously stated, in frames about three times
as deep as the others, say, about 8 inches deep; each frame may contain from
five to six skins (a bed of tan bark being between each); about 75 to 100 lbs.
tan to a skin weighing about 110 lbs. is a satisfactory proportion.
I now proceed to describe the mode of tanning soft skins, such as skins for
upper leather, calf skins, etc., or those of the description usually treated with
a running stream and a cream of lime bath. These skins are first unhaired

page_text: in a milk or cream of lime bath (in large vats), and washed in a running
stream, as is usually practised, after which they are stretched on a table or
frame, smoothed. and worked up by hand or otherwise into the form and
thickness desired. Each skin is then rolled up carefully and unrolled on to
a bed or layer of tan bark spread at the bottom of a shallow frame, and
another bed of bark or tan is spread on the top. The frame with the skin
between the two beds of tan is then lowered into the pit, and other frames
after it, each skin being in a separate frame. When a sufficient number of
frames have been placed into the pit it is covered over, steam let in and shut
off, and tanning liquor admitted, all as before described with reference to hard
hides. The operation is then repeated with deeper frames (say, with from
6 to 8 skins in each frame), and with beds of tan bark between each skin;
the ooze or tanning infusion should be about from 18 to 20 tenths. The
frame rim may be about between 2 and 3 inches; the weight of tan, say,
about 70 to 80 lbs. for a skin of about 100 lbs. weight. The weight of the
tanning liquors should be from 14th to 18th of the areometer. Skins should
be left in the pit for from 12 to 15 days for each operation.
Kid and sheep skins for gloves, etc. and all skins that have to be grained,
are washed in running water, as usual, then immersed and stirred about or
handled in a weak bath of liquid, after which they are laid in frames in
alternate layers of skins and tan bark (the latter being in sufficient quantity
to completely tan the skin), lowered into the pit, and treated as described for
the other skins, the tan liquor being at about 16 to 18th of the aerometer.
They will be completely tanned in about a fortnight, and ready to be dressed
by the currier.
And having now described the nature of the said Invention, and in what
manner the same is to be performed, I declare that I claim,-
First, the tanning of skins and hides without previously subjecting them to
the action of acids for the purpose of "raising" them or swelling the fibres.
Second, the mode herein-before described of steaming skins and hides, for
the purpose of loosening the hair or wool in tan pits, constructed as herein-
before explained with reference to the Drawings annexed.
Third, the method of tanning, herein-before described, in which each hide
or skin is first subjected singly to direct contact with the tan bark, and placed
separately between and in contact with two beds of tan bark in shallow
frames, and steam and tan infusion or liquor admitted, and the operation
repeated in deeper frames, all as herein-before described.
Fourth, the arrangement and construction of tan pits for carrying the
Invention into effect.

page_text: Fifth, the working up, shaping, or smoothing of skins and hides, as herein-
before described.
Sixth, the various processes and modes herein-before described for tanning
skins and hides.
In witness whereof; I, the said Etienne Sterlingue, have hereunto set my
hand and seal, this Tenth day of February, in the year of our Lord
One thousand eight hundred and fifty-seven.
E. STERLINGUE. (L.s.)
Witness,
CH. ARMENGAUD, Ing" Conseil,
No. 23, Boulevard de Strasbourg, à Paris.