AN IMPROVED PROCESS OF TANNING
Year: 1880

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for an Invention of "AN IMPROVED
PROCESS OF TANNING." A communication from abroad by Gaudenzio Dalla
Zonca, of Venice, in the Kingdom of Italy.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark
at the Office of the Commissioners of Patents on the 13th July 1880.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent.
"AN IMPROVED PROCESS OF TANNING." [A communication from
abroad by Gaudenzio Dalla Zonca, of Venice, in the Kingdom of Italy.]
This Invention has for its object to reduce the time required for tanning hides
and skins with the ordinary vegetable matters, and without having recourse to
chemical substances, which injure their quality. To this end the hides after
undergoing the depilatory operation, say, to the number of 175 pieces, weighing
(dry) about 400 kilogrammes, are placed in a number of casks together with about
130 kilos. of ground fir bark, which is distributed among the several casks,
according to the weight of the hides contained in each. The casks with the hides
are then immersed in an infusion of the same bark, in which the casks are rotated
for about 12 hours by steam power, and after this the hides are taken out and
drained. By this first operation the desired color is obtained.
The hides are then sewn together in pairs to form bags with the hair side.
outwards, leaving an opening either at the end, corresponding to the head of the
animal, or at any other point, such as at one of the legs, for example, at which to
introduce a mixture of oak bark, valonia, and fir bark in powder, in the proportion
of about 3%, kilogrammes per kilogramme of hide (dry). For 175 hides weighing
400 kilogrammes when dry I employ about 1100 kilogrammes of oak bark,
110 kilogrammes of valonia, and 250 kilogrammes of fir bark. I then put the
bags in a pit or large vat about half filled with an infusion or decoction of the
same substances, which may be used without changing for about 10 or 12 days.
The bags are then filled up with the cold liquor, the mouths closed by being
twisted and tied tightly; they are then laid horizontolly in the pit or vat, where
they remain half covered with liquor. The liquor is removed from the bags after
the lapse of an hour, and they are again filled up with liquor from the pit or vat.

page_text: The bark mixture remains in the bags until the operation is terminated. The
bags are again emptied of liquor after the lapse of another hour, and again filled up
with the same liquor, but in this case slightly heated by means of a small furnace
in communication with the vat.
The same operation is repeated five times at intervals of 2 hours, the tempe-
rature being raised to a higher degree each time until the hand can hardly bear
the beat. The bags require to be shaken from time to time throughout the whole
operation in order that the tanning principle of the contents may be developed
and caused to act uniformly.
After the above operations are terminated the bags are emptied of the liquor
they contain and laid at the bottom of the vat for the next 12 hours, after which
the same operation is recommenced with another batch of hides, which are laid
upon those in the vat. The first batch of hides is withdrawn at the end of the
-12-hours-and the bags unsewn. The hides will then be perfectly tanned, but in
order that they should not lose in weight they are again placed-in the casks and.
rotated for about 48 hours in a solution of 300 kilos. of oak bark and 100 kilos. of
fir bark for every 175 pieces weighing 400 kilos. in a dry state. The tanning
operation is thereby not only improved, but the loss in weight is reduced to a
minimum.
The above process is that employed for light skins, but it equally applies to
hides used for sole leather, except that after having divided them in the usual
manner they are piled one upon another in large vats, a layer of valonia being
pluced upon each in the proportion of 1%, kilos. per kilogramme of skin in a dry
state. At the end of 38 days the hides, if of medium weight, will be perfectly
tanned, but if they are very heavy they are, after the first 35 days, again sprinkled
with-valonia-in-the-same-proportion as before, and allowed to remain for another
35 days, when they will be thoroughly tanned.
By means of the above process light skins weighing about 13, kilogramines
may be tanned in 3 days instead of requiring from 4 to 5 months, as in ordinary,
while hides weighing from 3 to 4 kilogrammes occupy but 6 days instead of 5 to
6 months by the old process. Heavy hides are perfectly tanned in from 40 to
70 days, whereas hitherto they have required from 6 to 7 or from 8 to 10 months,
according to their thickness to obtain the same results.
The substances specified in the process before described are those which I prefer
to employ, but other substances may be used in lieu thereof, such as common
valonia, catechu, extract of chestnut, Müller tannin, myrabolans, or any other
vegetable substances possessing sufficient tanning power, and capable of affording
the same the same results.
Another advantage is that a gain of upwards of 10 per cent. in weight is
obtained as compared with the ordinary processes.

page_text: 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
13th January 1881.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent. "AN IMPROVED PROCESS OF TANNING." A communication from
abroad by Gaudenzio Dalla Zonca, of Venice, in the Kingdom of Italy.
This Invention has for its object to reduce the time required for tanning hides
and skins without having recourse to chemical substances, which impair their
quality, but merely using the vegetable substances ordinarily employed in tanning.
To this end the hides after undergoing the depilatory operation are placed, say, to
the number of 175 peices, weighing (dry) about 400 kilogrammes, in a series of
casks, together with about 130 kilos. of ground fir bark, which is distributed
among the several casks, according to the weight of the hides contained in each.
The casks containing the hides and bark are then immersed in an infusion of the
same bark, in which the casks are rotated for about 12 hours by steam power.
The hides are then taken out and drained. By this first operation the desired
color is obtained.
The hides are then sewn together in pairs to form bags with the hair side
outwards, leaving an opening at the neck, or at any other point, preferably at one of
the legs, at which to introduce a mixture of powdered oak bark, valonia, and fir
bark in the proportion of about 3 kilogrammes per kilogramme of hido (dry).
By leaving the opening at the leg the tanning materials are brought into direct
contact with the thickest parts of the hide towards the head, which are thus as
well tanned as the other parts. For 175 hides weighing 400 kilogramines when
dry I employ about 1100 kilogrammes of oak bark, 110 kilogrammes of valonia,
and 250 kilogrammes of fir bark. I then put the bags in a pit or vat about half
filled with an ooze of the saine substances, which may be used without changing
for about 10 or 12 days. The bags on being placed in the pit are filled up with
the same liquor, and the mouths closed by being twisted and tied tightly. They
are then layed horizontally in the pit, where they remain half covered with liquor.
The bags are emptied of liquor after the lapse of an hour, and are again filled up
with liquor from the pit. The bark mixture remains in the bags until the
operation is terminated.
The bags are again emptied of liquor after the lapse of another hour, and filled
up afresh with the same liquor, but in this case the liquor is slightly heated by
means of a small furnace in communication with the pit or vat.
The same operation is repeated five times at intervals of two hours, the tempe-
rature being raised to a higher degree cach time until the hand can hardly bear
the heat. The bags require to be handled from time to time throughout the whole
operation in order that the tanning principle of the contents may be developed
and caused to act uniformly.
After the abovo operations are terminated the bags are emptied of liquor only,
and laid at the bottom of the pit for the next 12 bours, after which the summe
operations are repeated with another batch of hides, which are subsequently laid
upon those in the pit.
The first batch of hides is withdrawn at the end of the 12 hours and the bags
unsown.
The hides will then be perfectly tanned, but in order that they shall not lose,
but rather gain, in weight, thoy are again placed in the casks and rotated for
bout 48 hours in a solution of 300 kilos. of oak bark and 100 kilos. of fir bark for
every 175 pieces weighing 400 kilos. in a dry state. The tanning operation is

page_text: thereby not only improved, but a gain of 10 per cent. is obtained over the weight
of hides tanned by the old process.
The above process is that employed for light skins, but it equally applies to
hides used for sole leather, except that after having divided them in the usual
manner they are piled one upon another in pits, a layer of valonia being placed
upon each, weight for weight of the skins in a dry state, and at the end of 50 days
the hides will be perfectly tanned.
By means of the above process light skins weighing (dry) about 13, kilo-
grammes may be tanned in 3 days instead of requiring from 4 to 5 months, as in
ordinary, while hides weighing from 3 to 4 kilogrammos occupy but 6 days instead
of 5 to 6 months by the old process. Heavy hides are perfectly tanned in from
40 to 50 days, whereas hitherto they have required from 6 to 7 or from 8 to
-10-months, according to their thickness, to obtain the same results.
The substances specified in the process before described-are-those which I prefer
to employ, but other vegetable substances may be used in lieu thereof, such as
common valonia, catechu, extract of chestnut, Müller tannin, myrabolans, or any
other vegetable substances possessing sufficient tanning power, and capable of
affording the saine results.
Having described the nature of the said Invention, and the manner of performing
the same, I declare that what I claim as the Invention to bo protected by the
herein before in part recited Letters Patent is,-
The improved rapid process of tanning with vegetable matters only, consisting
of the several successive steps or operations, substantially as herein described.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my baud and seal, this Thirteenth-day-of-January, A.D. 1881.