An Improved Method of Preserving and Tawing Skins,
Year: 1898

page_text: Date of Application, 18th Mar., 1898-Accepted, 29th Oct., 1898
COMPLETE SPECIFICATION.
An Improved Method of Preserving and Tawing Skins,
I, URY DE GÜNZBURG, of 52, Boulevard Lamouroux, Vitry-sur-Seine, Seine
Department, in the Republic of France, do hereby declare the nature of this inven-
tior. and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement:-
In the method to which the present invention relates the removal of the fleshy
fibre from the skin is obtained and putrescibility is prevented without the help or
the formation, during the operation, of any soluble and crystallizable salt, which
would have the effect of diminishing the strength of the skin. The result is that
skins thus treated contain none of the said cyrstallizable salts, remain permanently
flexible, and lose none of the strength they possessed before being treated.
Nor has water, whether cold or hot, any action whatever on a skin thus pre-
pared.
This new method makes the skin as firm, as supple, and as elastic as may be
required for any purpose for which it may be intended.
The application of my method also makes the skin white, and when the skin
has to be dyed the colours become rapidly and completely fixed on it.
The new method is applicable, on the one hand, to the preservation of skins of
different kinds, and on the other hand, to the tawing of certain of the said skins
either with or without the hair, wool, or feathers.
the skins; wool being
The method also improves the hair or the wool on
bleached without losing any of its strength, a great part of the foreign matter of
vegetable origin mixed up with the wool and decreasing its value, being removed.
My method of preserving and tawing skins may also be applied to either wet
or dry skins, the latter being soaked and restored to the state of hides.
In order to depilate the skins, they are put, for a time which depends on their
thickness, but which should in no case exceed one hour, in a water bath containing
one-third of its weight of sulphohydrate of calcium sulphide in a nascent state.
When removed from the bath, the skins may readily be freed, either mechanically
or by hand, from their hair or their wool, and also from the fragments of flesh
which may still adhere to them.
On the other hand, this treatment has the effect of causing the skins to swell
out considerably, so that they are then ready to undergo the operation of tawing.
The skins are then immersed in a bath containing one part of bisulphite of
alumina to ten parts of water, the skins being allowed to remain in the bath from
ten to forty minutes, according to their nature and thickness. The action of this
bath, due to the presence of sulphurous and hyposulphurous acids, which in the
nascent state, pass through the skin, and to alumina salt which completely
of the
impregnates the skin, has the effect of loosening the fibres
skin and of preparing it for the subsequent operations. The action of the said
bath may be rendered more vigorous by a very small addition of hydrochloric
acid intended to facilitate the liberation of the sulphurous and hyposulphurous
noide

page_text: When removed from the said bath, the skins are allowed to drain for a few
moments; they are then immersed in an ammoniacal bath, which produces a white
gelatinous persistent precipitate, the skins being taken out after a few moments
and left to drain. The liquid ammoniae added to the water to form the bath is
sufficient in quantity to produce the said precipitate.
In order to obtain skins which are closer and better prepared for dyeing, a
portion of a salt of chromium such as neutral chromate of soda may be added to
the ammoniacal bath.
Upon the completion of these operations, in order to dress the skins I cause them
to absorb within fulling mills à firm paste constituted by the mixture of eight
parts of wheaten-flour to one part of glycerine, to which latter is added a small
quantity of the residues of the precipitate of the ammoniac-bath in order to obtain
a sufficiently firm paste.
Such paste should be absorbed completely before removing the skins from the
fulling mills and before drying them, if they are intended to be used in a white
condition or before dyeing them, which operation may be undertaken at once with-
out further preparation.
The skins are then finished in the usual manner.
The qualities of preservation possessed by the skins treated by this method are
owing:
1st. To the deoxidation of the constituent matters of the skin, by the sulphurous
or sulphurous and hyposulphurous acids in a nascent state:
2nd. To the action of a small quantity of sulphur precipitated upon the surface
of the fibres of the skin in a nascent state.
3rd. To the action of the alumina precipitated on the surfaces of the fibres of
the skin and applied in the most suitable conditions for tawing. Owing to the
new constitution of the fibres, which are modified by the loss of oxygen, they aggre-
gate more intimately, thus increasing the closeness, the strength and the insolu-
bility of the skin, as is clearly shown by the contraction of the molecules of the
skin after having lost the oxygen. It is owing to the action which I have just
explained that the process is applicable not only to tawing skins, but also to the
preservation of skins of every kind, such preservation commencing, with the first
operations by which the skins are prepared for dressing, and being finished com-
pletely, as specified above, being capable of resisting any destructive action and
any putrefaction for an almost indefinite period.
The treatment to which the skins are submitted may thus be effected alone to
insure the indefinite preservation of the skins or it may be combined with the
tawing in order to obtain a degree of perfection which has not hitherto been
attained.
Owing to the presence of chlorides in the first bath a very brilliant bleaching is
obtained. I therefore wish it to be understood that my process includes the use
of the substances mentioned and of congenerous substance for the preservation of
hides and skins of every kind for bleaching and tawing them, and consequently,
the bleaching and cleaning of the wool and hair of such skins, these results being
obtained by the action of the chloride of aluminium formed after the second
operation.
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:
(1) A process for treating skins without the help or the formation of any soluble
and crystallizable salt essentially characterized by the fact that the skins treated
may be kept indefinitely without returning to their natural state and without
losing in suppleness or strength, being likewise unaffected by the action of cold or
hot water, the said process consisting essentially

page_text: (a) In taking previously shaved skins or skins in either a dry or fresh condition
and immersing them in water in order to convert them into shaved skins or hides.
(b) In submitting them for the requisite time but in any case for less than an
hour, to the action of a bath consisting of three parts of water to one part of
sulphohydrate of calcium sulphide in a nascent state.
(c) In depilating the skins and freeing them from adhering flesh either by
hand; or mechanically.
(d) In tawing the skins if they are to be tawed.
(e) In immersing the skins thus tawed, or after they have undergone the first
three operations, in baths consisting of ten parts of water to one part of bisul-
phite of alumina, to which according to circumstances and to the nature of the
skin, a small quantity of hydrochloric acid may be added which will facilitate the
liberation of hyposulphurous and sulphurous acids.
(In removing the skins from the bath and allowing them to drain.
(g) In immersing the skins for a short time in a final bath of water to which is
added liquid ammoniac which forms a persistent gelatinous white precipitate the
said bath advantageously containing a salt of chromium and, preferably a neutral
chromate of soda.
(h) In allowing the skins to drain thoroughly.
(2) In putting the skins into fulling-mills, with a firm paste consisting of eight
parts of wheaten flour, one part of glycerine and the residues of precipitation of
the ammonia bath and in causing the fulling mills to operate, until complete
absorption of the mixture takes place.
() In dyeing the skins if desired, and in subsequently treating them by the
well known processes and preparation.
(2) In the process for the treatment of skins for preserving and tawing them in
accordance with the preceding claim, the special use under the stipulated condi-
tions of baths of hyposulphate of sulphide of calcium in a nascent state of bisul-
phite of aluminium with the addition of hydrochloric acid and of liquid ammonia
with the addition of neutral chromate of soda, substantially as described.
(3) In the process for the treatment of skins for preserving and tawing them,
the employment of a paste of wheaten flour and glycerine for incorporation in the
skins by means of a mechanical operation, substantially as described.
Dated this 18th day of March 1898.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.