Improvements in the Treatment and Tanning of Hides and Skins.
Year: 1899

page_text: Date of Application, 27th June, 1899-Accepted, 9th Dec., 1899
COMPLETE SPECIFICATION.
Improvements in the Treatment and Tanning of Hides and Skins.
I, LUIGI CONSONNO, of Como, Italy, Manufacturer, do hereby declare the nature
of this invention and in what manner the same is to be performed, to be particu-
larly described and ascertained in and by the following statement:―
This invention relates to improvements in the unhairing and preliminary treat-
ment and tanning of hides and skins, and is easily applicable in all its operations
and effective in converting in two or three days haired skins or hides into tanned
skins or hides and in very economically obtaining products of the highest quality
and best appearance and possessing all the attributes of the very best feather
produced by the best tannings of very long duration.
The improved system also has the advantage of allowing the preparatory work
to be done according to two distinct methods adapted to meet different require-
ments, that is to say either with lime and various soluble salts for the purgation,
or with soluble salts without lime, avoiding thus the formation and precipitation
of tannate of lime and the consequent considerable loss of tannin, the latter method
being applied to the unhairing and preparing operations, when, in the after treat-
ment, I use soda salts, ammoniacal solutions, benzine or carbonic acid under
special conditions of temperature and of combinations which have not hitherto
been used; I then effect the tanning in a limit of time of from three to thirty
hours according to the quality of the product desired to be obtained, using revolving
containers such as heretofore employed, but applying thereto a suitable means
of rotating the same in opposite directions, and using extracts of different qualities
applied in their ordinary state of manufacture, that is to say, such as found in
commerce, without addition or dilution, and afterwards effecting the finishing
according to the various systems demanded by the numerous applications for which
the products are intended; since, without any difference from such systems even
the oldest, the skins or hides tanned by the improved process are very susceptible
to any kind of finishing by virtue of the improved process of preparation of the
skin for the tanning.
'
For the unhairing, the skins fresh or brought to a fresh state, are submitted
to a solution of soluble salts alone or in combination with lime, at a temperature
of about 50-60 degrees Centigrade or more; the operation being carried out in
vessels of stone, wood or iron, if the semi-rapid process be employed; and in
rotating containers if the quickest process be employed, which has not been done.
hitherto.
The soluble salts have soda as their base, sodium sulphide and soda crystals
being mentioned by way of example, and are used in quantities known to be neces-
sary to obtain the desired effect in proportion to the strength and consistency of
the hair to be treated.
According to the requirements of the product to be obtained, I commence the
treatment of the skins or hides by one or other of these preliminary operations,
in a well determined manner.
I employ the soluble salts alone, when I want to obtain the best result in weight
and the depilation in a very limited time, say 45 minutes or even much less; this

page_text: L
application attaining the end of destroying the hair of the hide or skin without
the assistance of milk of lime and fermentation; being based on the violent
agitation or fulling in a suitable vessel or container having a rotative motion
in which the treating liquid can preferably be introduced without stopping it.
The hides or skins, once in the cask put in motion and receiving a number of
turns according to its diameter and after ten minutes washing in pure water in
quantity about the weight of the hides or skins, are submitted to a solution
composed of 83 p. c. pure water, 12 p. c. of commercial sodium sulphide, 4 p. c. of
soda crystals, and 1 p. c. of biiodide of mercury, the solution being well mixed, kept
at 50-60 degrees Centigrade and introduced as aforesaid into the cask if possible
while in motion, in the proportion of ½ of the weight of the hides or skins, and
being kept in contact therewith for a time which may vary from 5 to 45 minutes,
according to the different qualities and thicknesses of the hides or skins; after
which they are washed, scoured and passed to be fleshed.
'
On the other hand, I use the soluble salts in combination with lime when I
desire to obtain a better result as regards suppleness and colour rather than a
maximum increase in weight, because, evidently, the decomposition of the fibrine
or the lixiviation of the fibres of the hide or skin is more considerable. I carry
out the treatment in the said vessels of stone, wood or iron by placing therein the
hides or skins, which should remain covered by the solution referred to, milk of
lime and arsenic being added thereto in any suitable proportions; the hides or skins
should be agitated once or twice during the operation the duration of which may
vary from 6 to 18 hours according to the quality of the hides or skins and the
nature of the hair. But, I can also carry out the treatment in a rotating con-
tainer, obtaining the unhairing in % of an hour, and even less, proceeding in
the manner described for the extra-rapid process.
I then effect the cleaning and fleshing of the skins by hand or by machinery
according to circumstances and to the apparatus at command.
The operations of scouring and final washing of the skins (so as to make the
same ready for forced tanning by the application from the very start of extracts
of full normal strength) are alternately effected in a revolving barrel, or if neces-
sary in fulling apparatus or vessels, supplied with a sufficient quantity of clean
water, the operations being conducted in every case according to the method best
suited to the product to be ultimately obtained, taking care that in every detail
of working there is the complete elimination of saline or alkaline (basic) solutions,
but employing different quantities of solvents containing soda preparations and of
ammonia solutions and of benzine, or carbonic acid gas, in proportions carefully
determined with reference to the weight, nature and thickness of the skins to be
treated, and avoiding an excessive diminution of the fatty matters which surround
the corium or dermis of the skin and protect the epidermis, whilst yet causing the
most efficient condition of the pores for the tanning.
Having seen that the container is quite clean, I place the skins therein and,
after a washing with clean water, apply a solution of 2% of soda in crystals or any
other basic preparation of soda; 05% of commercial liquid ammonia, and
05% of Benzine, and I leave the whole until the operation is complete, the
time depending on the nature and thickness of the hides or skins under treat-
ment, or I use, for the better dissolution of the alkaline substances, carbonic acid
gas with which I saturate ordinary water and pass the hides or skins therethrough
as above described.
The main object of this improved preparatory treatment of the hides or skins
is to produce suppleness or softness with the necessary but not any excessive
swelling, so that they can, in the first instance, take to tannic solutions in the
highest degrees of concentration, as they are found in commerce, keeping in all
their best conditions of morphological predisposition, the most rational and best
suitable for the absorption of the tanning matters.
I regulate the duration of all these operations in such manner as to attain the
improvement hereunder claimed, avoiding a prolonged contact of the dissolving

page_text: olutions with the hides or skins and consequently any weakening of the bre
ubstances as a whole, which progressively is produced by reason on fermentation,
ne latter in its turn being caused of necessity partly by the organic germs presen
n the hide or skin and partly by germs present in the atmosphere.
It is thus that I prepare the hides or skins and in a manner to obtain as desired
he best result in weight and a leather of firmness and solidity only hitherto
obtained by the best tannings of very long duration.
The preparatory treatment being finished, 1 use, for the tanning operation,
cylindrical receivers or containers such as those long adopted in many tanneries
and adapted also tor tanning with dilute tannic extract solutions; but, to the
receivers, apply means for rotating them in opposite directions, that is to say
for obtaining the rotation as desired alternately from right to left and vice versu;
in the said receivers the hides or skins with the tannic extracts which I use from
the beginning in their normal state of concentration, undergo absorption, partly
in consequence of chemical effects under the action of the combination of the
astringent substances with the hide or skin rendered pure in accordance with the
described preparatory treatment and partly in consequence of the physical effects
produced by the strong penetration of the solutions into the interstices of the
Tissues of the hide or skin brought about by the movement in opposite directions,
of all together.
I thus constitute an essential characteristic in the improved system of preparing
the hide or skin in connection with the violent tanning which i effect, and by the
rotation of the receiver alternately in opposite directions, thus clearly marking a
complete change in the process of treatment.
The quantity and the quality of the hides or skins to be introduced in each
receiver is proportionate or suitable to its size; I introduce into the receiver a
quantity of tannic extract, such as is found in commerce and which is normally
of 25 degrees Beaumé, never more than twelve hundred grammes for each kilo-
gramme of fresh hide or skin, adding thereto at the most a little animal or vegetal
oil according to the products desired to be obtained.
In addition to the special preparation enabling me to effect the complete tau-
ning in a minimum space of time, converting in from two to three days haired
consider as useful--in
hides or skins in a fresh state into tanned hides or skins,
addition only the production of vacuum in the rotative receiver by means of a
pneumatic pump or the lowering of the temperature by an injector of cold air or
an exhauster of hot air; these supplementary operations however only rendering
certain advantages with regard to economy of time, and can be omitted at will
and are not therefore indispensable to the process.
The constant rotation of the receiver wherein the tanning is effected is not
necessary and stoppages do not cause any harm to the hides or skins.
The necessary apparatus for my improved system are those most usually
employed in tanneries; it only being necessary to adapt them for motion in
opposite directions and any container would be utilizable; the objects I have
proposed to obtain have been specially studied with a view of utilizing existing
devices found in most tanneries, thus facilitating the application of my improved
system with economy by avoiding radical modifications or new constructions.
The results which I obtain are thus perfect, the products being speedily and
economically obtained and of the highest quality and best appearance and possess-
ing every required durability and all the attributes of the very best leather, and
O sole leathers also of a density firmness and solidity hitherto obtained only by
the best tannings of very long duration.
55
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
The herein described improvements in the treatment and tanning of hides
and skins, the same being characterized:-

page_text: (a) By the treatment of hides or skins in preparation at a degree of heat of
from 50-60 degrees Centigrade-even more rendering the hides or skins com-
pletely predisposed for violent and perfect tanning and consequently to the
absorption, from the first, of tanning solutions of normal concentration such as
found in commerce, thus permitting of the conversion in two or three days of
haired hides or skins in a fresh state, into tanned hides or skins.
(b) By the facility with which the hides or skins may be unhaired by two
methods differing according to the needs and requirements of the product:
either the method which can be carried out in 3 of an hour or even less, by using
rotating receivers never before used for such purpose, or the method which can
be carried out in 6 to 18 hours in vessels: by the addition of substances, or their
variation with reference to their physical action or a reduction or increase of the
mixed salts, the reduction of the biiodide of mercury, the substitution for the
soda crystals or for biiodide of mercury of other salts having the like effect; the
same considerations being observed as to the operation of preparing the hides or
skins for the treatment with soda crystals, amnionia and benzine or carbonic acid.
(c) By the great advantage in the operation of tanning obtained by the applica-
tion from the first, of tanning extracts in their normal state of concentration and
in quantity not exceeding in any case twelve hundred grammes for each kilo-
gramme of fresh hide or skin.
(By the rotation, in opposite directions, of the receiver which should turn
alternately from right to left and vice versa, and, if desired, by the formation of
vacuum, by the injection of cold air or by the aspiration of hot air,--in special
cases, advantageous actions, when duly applied with the view of avoiding the
production of an excessive heat and with the object of obtaining the hide or skin
tanned free from liability of corruption or chemical alteration.
All substantially as hereinbefore described.
1000
DAY, DAVIES & HUNT,
Chartered Patent Agents,
321, High Holborn, London, W.C.,
Agents for the Applicant.