IMPROVEMENTS ON DEPILATION AND LEATHER TANNING
Year: 1867

page_text: LETTERS PATENT to Charles Erba, Chemist, of Milan (Italy), for the
Invention of "IMPROVEMENTS ON DEPILATION AND LEATHER TANNING."
Sealed the 13th December 1867, and dated the 15th June 1867.
PROVISIONAL SPECIFICATION left by the said Charles Erba at the
Office of the Commissioners of Patents, with his Petition, on the 15th
June 1867.
I, CHARLES ERBA, Chemist, of Milan (Italy), do hereby declare the nature
of the said Invention for "IMPROVEMENTS ON DEPILATION AND LEATHER TANNING,"
to be as follows:-
The object of this Invention is to produce better leather than heretofore, to
economize the tanning materials, the time employed in tanning, and to obtain
the greatest possible produce of leather from a given quantity of skin. From
the study of the tanning of skins I have proved two facts, first, that tannin
combines almost instantaneously with the fibrous and gelatinous constituents
of the skin when it is in contact therewith under the most favorable conditions ;
second, that leather is so much the better in proportion to the speed with which
it is tanned. On this data I have established the theory of my process for
improving leather by shortening the tanning process, and which I will now
describe.
The cleansing or depilation.-The skins to be cleaned or to have the hair
removed therefrom may be fresh, salted, or dry; the latter must be brought
to a similar state as the fresh skins before preparing them for the cleansing or

page_text: depilation. The operation consists in soaking the skins in a bath composed
of the following ingredients:-Ninety-six parts of water, two parts of carbonate
of soda, and two parts of hydrated oxide of lime, and reduced to a milky state.
After several hours immersion in this liquid the skins are ready to be cleansed
or depilated, and which is accomplished in the ordinary manner.
The distension and softening.-The skins being well stripped of hair and
washed in running water are afterwards immersed for from four to ten hours,
according to the nature and the thickness of the skins, in a bath composed of
a hundred parts water and a half of ammoniacal liquid. Instead of this a
bath of ammoniacal carbonate may be substituted containing one per cent. of
the said salt. The skins when taken from these baths are washed in running
water, and afterward a hand with the round knife is passed over them to
express the water they have imbibed, after this operation the skins are ready
to be submitted to the tanning process.
The tanning. After the treatment above described the skins are immersed
in a first bath of tannin marking two to four degrees of density, Beaumé, which
is obtained by treating the vegetable tanning materials by displacement (la
methode de displacement). In this bath the skins remain from ten to fifteen
days according to their nature and thickness. The operation may be considered
finished when the liquor has penetrated to the centre of the skin; the skins
are then placed in a second bath of tannin marking six to seven degrees of
density, Beaumé, obtained by the preceding process. Four to six weeks of
immersion in this liquid, according to the quality and thickness of the skins,
is sufficient to perfect the tanning even for skins of the greatest thickness.
The leathers being removed from this strong bath are allowed to soak for
twenty-four hours in a tannin bath marking about two degrees Beaumé, after
this the leathers are ready for the currier. By my process the cleansing and
softening of the skins is obtained in a few hours, and the tanning proper in
from four, six, or ten weeks, according to the thickness and quality of the skins.
Leathers thus obtained are of a superior quality, and the produce in leather is
greater than is produced by the ordinary tanning.
It must be understood that I reserve to myself the right of employing in the
different operations herein-before given not only doses or varying proportions
of the substances given, but that I can also employ other substances producing
similar or analagous results.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Charles Erba in the Great Seal Patent Office on the 14th
December 1867.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
ERBA, Chemist of Milan, Italy, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fifteenth day of June, in the year of our Lord One
thousand eight hundred and sixty-seven, in the thirtieth year of Her reign,
did, for Ierself, Her heirs and successors, give and grant unto me, the
said Charles Erba, Her special licence that I, the said Charles Erba,
my executors, administrators, and assigns, or such others as I, the said
Charles Erba, 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,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS ON
DEPILATION AND LEATHER TANNING," upon the condition (amongst others)
that I, the said Charles Erba, 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 Charles Erba, do hereby declare
the nature of my 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 Drawings hereto annexed and to the
letters and figures marked thereon, that is to say:-
The object of this Invention is to produce better leather than heretofore, to
economize the tanning materials, the time employed in tanning, and to obtain
the greatest possible produce of leather from a given quantity of skin. Froni
the study of the tanning of skins I have proved two facts, first, that tamnin
combines almost instantaneously with the fibrous and gelatinous constituents
of the skin when it is in contact therewith under the most favorable con-
ditions; second, that leather is so much the better in proportion to the
speed with which it is tanned. On this data I have established the theory
of my process for improving leather by shortening the tanning process, and
which I will now describe.

page_text: The cleansing or depilation.-The skins to be cleansed or to have the hair
removed therefrom may be fresh, salted, or dry; the latter must be brought to
a similar state as the fresh skins before preparing them for the cleansing or
depilation. The operation consists in soaking the skins in a bath composed
of the following ingredients:-Ninety-six parts of water, two parts of carbo-
nate of soda, and two parts of hydrated oxide of lime, and reduced to a milky
state. After several hours immersion in this liquid the skins are ready to be
cleansed or depilated, and which is accomplished in the ordinary manner.
The distension and softening.-The skins being well stripped of hair and
washed in running water, are afterwards immersed for from four to ten hours,
according to the nature and the thickness of the skins in a bath composed of a
hundred parts water, and a half of ammoniacal liquid. Instead of this a bath
of ammoniacal carbonate may be substituted containing one per cent. of the
said salt. The skins when taken from these baths are washed in running
water, and afterwards a hand with the round knife is passed over. them to
express the water they have imbibed, after this operation the skins are ready
to be submitted to the tanning process.
The tanning. After the treatment above described, the skins are immersed
in a first bath of tannin, marking two to four degrees of density, Beaumé,
which is obtained by treating the vegetable tanning materials by displacement.
In this bath the skins remain from ten to fifteen days, according to their nature
and thickness. The operation may be considered finished when the liquor has
penetrated to the centre of the skin. The skins are then placed in a second
bath of tannin, marking six to seven degrees of density, Beaumé, obtained by
the preceding process. Four to ten weeks of immersion in this liquid, according
to the quality and thickness of the skins, is sufficient to perfect the tanning
even for skins of the greatest thickness. The leathers being removed from
this strong bath are allowed to soak for twenty-four hours in a tannin bath,
marking about two degrees, Beaumé, after this the leathers are ready for the
currier. By my process the cleansing and softening of the skins is obtained
in a few hours, and the tanning proper in from four, six, or ten weeks, according
to the thickness and quality of the skins.
The process of tanning which I have just described still requires much
space, hand labour, and immersing vats. With the view of avoiding these
inconveniences, and at the same time of obtaining better and more economical
results, I have introduced a vat or tanning vessel, in which the skins being
laid flat are continually in contact with a tanning liquid at a strong and con-
stant density during the whole tanning process; it is necessary therefore to
provide such a displacing vat or vessel as to be capable of furnishing a liquid

page_text: always at the same degree of saturation by new editions of the tanning
elements in proportion as they become absorbed by the skins during the
progressive advance of the tanning, without disarranging the layers of skins
in the vat or vessel until the tanning is complete. This result I obtain
by means of an apparatus which I call a displacing vat or [vessel, with an
intermittent motion of the liquid at a constant density, which I am about

page_text: The vat or vessel A being filled to four-fifths of its height with alternate
layers of skins and tanning substances, the last of which for about two inches
is covered with a thick fabric and a wood grating kept fixed by weights, the
tanning liquid is then introduced by means of the tube m, n, previously
obtained by the displacement method at a density of five to six degrees in
sufficient quantity to extend from eight to ten inches from the surface of the
last layer. With this arrangement all the mass composed of skins and tanning
materials are immersed in the liquid. In this state the apparatus is left at
rest for twenty-four hours, then by means of the opening in the tape the liquid
is set in motion, which by its gravity flows into the reservoir B, and is raised
by a pump H into the vat A by the pipe m, n. This operation is done twice
in the first week, and afterwards during forty to sixty days once each two
days, after this lapse of time the skins will be completely tanned and trans-
formed into leather, but before withdrawing them the liquid in the vat A is
run off, leaving the mass to drain for twenty-four hours. The liquids thus
obtained will serve for other successive operations, avoiding in this manner the
preparation of new liquids by the displacing method. The residue of the
tanning materials being removed from the vat A, can be afterwards treated
by the displacing method to extract from it all the active principles which they
still possess; the liquids thus obtained of a density from two to four degrees
serve for a first immersion, as I have previously shown, or by dispensing with
this immersion the same substances may be directly employed to prepare a
first tanning vat or vessel, in which the skins without any other operation are
laid in layers after having received the first ammoniacal bath described; in
this case care must be taken to have previously arranged an apparatus inde-
pendent of the first, and after fifteen or twenty days the skins may be removed
from this first apparatus to be replaced in a second with the new tanning
materials as before described. I would observe that in this first operation the
displacing vat A will be filled with water or weak liquid (obtained by the
washing of the old materials) up to about eight inches above the last layer,
and these liquids must be introduced by the air pipe a, b, thus determining an
ascentional motion of the liquids in the vat A. In this condition the vat A
must be allowed to rest four days, and afterwards the liquids are allowed to
flow to raise them into the reservoir D, to pour them afresh into the appa-
ratus A, which will be allowed to rest for two days, afterwards the liquids
must be allowed to run once in two days for fifteen to thirty days according
to the quality and thickness of the skins. With these modifications just

page_text: described, which do not in any way alter the theory on which my method of
tanning is founded, the same results are obtained, whether for quality or for
the relative produce of the leather; the two operations are obtained, the pre-
paration of the liquid and the tanning in a single receiver, and at the same
time a considerable economy of space and hand labour are effected as well as
a great regularity in the progress of the operation with a similar economy of
time, seeing that it can be accomplished in the brief space of from fifty to
ninety days, according to the quality and thickness of the skins. Leathers
thus obtained are of a superior quality, and the produce of leather is greater
than by the ordinary tanning process.
I would have it understood that I reserve to myself the right of employing
in the different operations indicated, not only doses where the proportions of
the substances vary, but that I can also use other substances producing
similar or analagous results.
And having now described the nature of my said Invention, and in what
manner the same is to be performed, I declare that I claim, the new or
improved method of and apparatus for preparing, unhairing, and tanning skins
or hides, substantially as herein-before described and illustrated in the accom-
panying Drawings.
In witness whereof, I, the said Charles Erba, have hereunto set my
hand and seal, this Ninth day of December, in the year of our Lord
One thousand eight hundred and sixty-seven.
CARLO ERBA. (LS.)