IMPROVEMENTS IN THE TANNING OF HIDES OR SKINS, AND IN THE LEATHER PRODUCED THEREBY
Year: 1882

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
& Co., Patent Agents, Southampton Buildings, London, for an Invention of
"IMPROVEMENTS IN THE TANNING OF HIDES OR SKINS, AND IN THE LEATHER
PRODUCED THEREBY." A communication from abroad by Charles Vander-
straeten, of Jomapes, Belgium, Tannor.
PROVISIONAL SPECIFICATION left by the said William Robert Lake at
the Office of the Commissioners of Patents on the 30th January 1882.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co. Patent Agents,
Southampton Buildings London. "IMPROVEMENTS IN THE TANNING OF HIDES OR
SKINS AND IN THE LEATHER PRODUCED THEREBY." [A communication from
abroad by Charles Vanderstraeten, of Jemapes, Belgium, Tanner.]
The tanning of hides or skins by the employment of mineral salts is preferable
to vegetable tanning for the reason that it is more economical and more rapidly
effected whilst vegetable tanning is essentially superficial. Two disadvantages
are however incident to such tanning that is to say Firstly the leather produced
is of a color or shade which is not agreeable and is entirely or partially
unknown commercially and secondly, whatever may be the means employed
for eliminating from the hides or skins the mineral substances employed in the
tanning of the same there is always a residue of such substances which only escapes
by degrees in proportion as the deliquescent action of these substances that takes
place.
This Invention has for its object to remedy or obviate these disadvantages by
the employment of means which considered by themselves and taken separately are
known in the art of tanning but which have not heretofore been employed in.
combination in effecting mineral tanning
These means are as follows that is to say :-
Firstly In order to impart to the hides or skins the desired color I first submit
the same to vegetable tanning so as to impart to the said hides or skins such colour
prior to their being subjected to the mineral tanning and

page_text: Secondly. In order to render insoluble the mineral substances which remain in
the hides or skins after the tanning of the same I impregnate the said hides or
skins with glue or gelatine which combines with the said inineral substances and
retains the samo; at the same time this gelatine becomes insoluble by reason of
its combination and remains in the leather so as to strengthen or improve the
same.
The combination of the two tannings namely the vegetable and the mineral
tannings, results in the production of leather which is of the desired shade or colour
and is rapidly tanned throughout its entire thickness. The mineral tanning
completed by the treatment with gelatine furnishes leather which is well tanned
and strengthened or improved and in which all the insoluble mineral substances are
rendered insoluble In fact the entire process comprising as it does three successive
stages in the treatment of the hides or skins namely the vegetable tanning, the
mineral tanning, and the treatment of the hides or skins with gelatine produces
leather which is thoroughly tanned and strengthened or improved and well adapted
for commercial use by reason of its dye or color.
I will now proceed to describe in detail the manner in which the said invention
may be practically carried into effect.
The skins or hides properly washed or scoured and deprived of the materials
employed for removing the hair therefrom, are subjected to solutions of vegetable
tannin or tanning material suitably proportioned to afterwards withstand the
subsequent chemical treatment and give by the continuation of this treatment the
desired color. I preferably employ for this purpose valonia catechu and other
similar or analogous vegetable tanning materials. For example assuming two baths
to each contain three cubic metres for treating hides or skins by a vat of twelve, I
employ for the whole, five kilogramines of valonia which is caused to boil in order
to extract from it the tannin which it contains. The skins or hides are left in the
first bath for about a day and then left in the second bath which is a little stronger
than the said first bath for the same period. When the baths become weak or
impaired I strengthen the same by bringing them up to their original density. I
prefer to employ the vats ordinarily termed "coudreuses."
The vegetable tanning effected by means of the valonia imparts to the leather an
iron grey tint or colour. By the subsequent mineral tanning by means of
bichromate of potash which constitutes the second part of the process this iron-grey
colour or tint is transformed into a mahogany tint or shade.
If it is desired to produce a color or tint approaching more nearly to the
ordinary colour of leather I replace one half of the valonia by an equal quantity
of mimosa.
In all cases I vary the proportion of the ingredients used, the duration of the
operation, and the composition of the baths, to suit the colour which it is desired to
obtain.
The skins or hides thus coloured superficially are subjected to mineral tanning
in baths of alum, sulphate of alumina, chromate, iron salts or any other nineral
substances possessing tanning properties. I prefer however to employ bichromate
of potash.
The skins or hides are first subjected to the action of a feeble or weak bath of a
density of about from one hundred and two and a half (102) degrees to one
hundred and three and a half (1034) degrees; they are frequently raised and
moved or stirred so that the chemical action, with a view to the colour and the
touch of the hair or grain side of the skin, may be accomplished systematically and
uniformly, one or two hours being ordinarily sufficient for this purpose. If the
operation is properly carried into effect the leather produced will have a fine graiu,
the grain or hair side of the skin will be soft to the touch, and the swelling is
perceptible although not excessive. The colour or tint previously obtained is also
modified so that it becomes fast and will not change.
After this first mineral treatment the hides or skins are immersed in a second
and stronger bath of 105 degrees or less, composed of the same materials as the

page_text: first bath or differently. The skins or hides are suspended in this bath and have
imparted to them a gentle and regular movement. The action of this bath upon
the skins or hides is allowed to proceed until the same are completely and uniformly
penetrated, this action requiring not more than from twelve to fifteen days.
The tanned skins or hides are then withdrawn from the baths or vata, left to
drain, and well washed after which they are subjected to considerable pressure by
suitable means such for instance as a hydraulic press whereby a very large
proportion of the chemical substances or materials is extracted or eliminated.
Some of the latter however always remains in the skins or hides and is rendered
insoluble by treating the said skins or hides with gelatine.
Tho gelatine bath is prepared in the ordinary manner from the cuttings of fresh
hides or skins, And is heated so that the gelatine will not solidify. Into this bath
the tanned hides or skins as they leave the press aro immersed. The said hides or
skins impregnated with this gelatine are then placed in a fulling-machine wheroin
they are allowed to roll for about an hour that is to say until the leather has
entirely absorbed the gelatine. The gelatine which is thus caused to penetrate the
leather renders insoluble the bichromate of potash or other mineral materials or
substances remaining in the same and in addition improves such leather and
strengthens it in the hollow parts. Such gelatine moreover replaces the natural
gelatine which has been dissolved to a greater or less extent by the prior treatment
to which the skin or hide has been subjected.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent_and
of an Order of the Lord Chancellor filed by the said William Robert Lake
in the Great Seal Patent Offico on the 21st August 1882.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN THE TANNING OF ПIDES OR
SKINS, AND IN THE LEATHER PRODUCED THEREBY." A communication from
abroad by Charles Vanderstraeten of Jemapes, Belgium, Tanner.
The tanning of hides or skins by the employment of mineral salts is preferable
to vegetable tanning for the reason that it is more economical and more rapidly
effected, whilst vegetable tannin does not tan the whole thickness of the leather.
Two disadvantages are, however, incident to such mineral tanning, that is to
say Firstly, the leather produced is of a colour or shade which is not agreeable
and is entirely, or to a great extent, unknown commercially; and secondly,
whatever may be the means employed for eliminating from the hides or skins the
mineral substances employed in the tanning of the same, there is always a residue
of such substances which only escapes by degrees in proportion as the deliquescent
action of these substances takes place
The object of the said Invention is to obviate these disadvantages by the
employment of means, which, considered by themselves and taken separately, are
known in the art of tanning, but which have not heretofore been employed in
combination in effecting mineral tanning.
The means I employ are as follow, that is to say-In order to impart to the
hides or skins the desired colour I first submit the same to vegetable tanning which
colours them prior to their being subjected to the mineral tanning. In order to
render insoluble the mineral substances which remain in the hides or skins after
the tanning of the same, I impregnate the said hides or skins with glue, size, or
gelatine which combines with the said mineral substances and retains the same;
at the same time this gelatine becomes insoluble by reason of its combination and
remains in the leather so as to strengthen and improve the same by filling up the
pores therein.
The combination of the two tannings, namely the vegetable and the mineral
tanning, results in the production of leather which is of the desired shade or colour
and is rapidly tanned throughout its entire thickness. The mineral tanning
completed by the treatment with gelatine furnishes leather which is well tanned,
strengthened and improved, and in which all the mineral substances are rendered
insoluble, and the entire process, comprising as it does three successive stages in
the treatment of the hides or skins, namely, the vegetable tanning, the mineral
tanning, and the treatment of the hides or skins with gelatine, produces leather
which is thoroughly tanned, strengthened and improved and well adapted for
commercial use by reason of its colour.
I will now proceed to describe in detail the manner in which the said invention
may be practically carried into effect.
Tho skins or hides, properly washed or scoured and deprived of the materials
employed for removing the hair therefrom, are subjected to the action of solutions
of vegetable tannin suitably proportioned to withstand the subsequent chemical
treatment and give, by reason of this treatment, the desired colour. I preferably
employ for this purpose valonia, catechu, or analogous vegetable tanning materials.
For example assuming two baths to each contain three cubic metres, for treating
twelve hides or skins in each vat or basin, I employ, for the whole, fivo
kilogrammes of valonia which is caused to boil in order to extract from it the

page_text: tannin which it contains. The skins or hides are left in the first bath for about a
day and then left in the second bath which is a little stronger than the first for
the same period. When the baths become weak or impaired I strengthen the same
by bringing them up to their original density. I prefer to employ the vats
ordinary termed "coudreuses," or tan-vats.
The vegetable tanning effected by means of the valonia imparts to the leather au
iron-grey tint or colour. By the subsequent mineral tanning by means of
bichromate of potash, which constitutes the second part of the process, this
iron-grey colour is transformed into a mahogany tint or shade.
If it is desired to produce a colour or tint approaching more nearly to the
ordinary colour of leather, I replace one half of the valonia by an equal quantity of
inimosa. In all cases, I vary the proportion of the ingredients used, the duration
of the operation, and the composition of the baths, to suit the colour which it is
desired to obtain.
The skins or hides thus coloured superficially are subjected to mineral tanning in
baths of alum, sulphate of alumina, chromate, iron-salts, or any other mineral
substances possessing tanning properties. I prefer, however, to employ bichromate
of potash.
"
The skins or hides are first subjected to the action of a weak bath of a density
of about from one hundred and two and a half (102) degrees to one hundred and
three and a half (103) degrees Baumé; they are frequently raised and moved or
stirred so that the chemical action (with a view to the colour and the " " touch of
the hair or grain 'side of the skin) may be accomplished systematically and
uniformly, one or two hours being ordinarily sufficient for this purpose. If the
operation is properly carried into effect the leather produced will have a fine grain,
the grain or hair side of the skin will be soft to the touch and the swelling is
perceptible although not excessive. The colour or tint previously obtained is also
modified so that it becomes fast and will not change.
After this first mineral treatinent, the hides or skins are immersed, in a second
and stronger bath of 105 degrees Baumé, or less, composed of the same materials as
the first bath, or differently. The skins or hides are suspended in this bath and
have imparted to them a gentle and regular movement. The action of this bath
upon the skins or hides is allowed to proceed until the same are completely and
uniformly penetrated, this action requiring not more than from twelve to fifteen
days.
The tanned skins or hides are then withdrawn from the baths or vats, left to
drain, and well washed, after which they are subjected to considerable pressure by
suitable means, such for instance, as a hydraulic press, whereby a very large
proportion of the chemical substances or materials is extracted or eliminated. Some
of the latter, however, always remain in the skins or hides and require to be
rendered insoluble by treating the said skins or hides with gelatine.
The gelatine bath is prepared in the ordinary manner from the cuttings of fresh
hides or skins and is heated so that the gelatine will not solidify. Into this bath
the tanned hides or skins, as they leave the press, are immersed. The said hides
or skins impregnated with this gelatine are then placed in a fulling-mill wherein
they are allowed to roll for about an hour, that is to say, until the leather has
entirely absorbed the gelatine. The gelatine which is thus caused to penetrate the
leather renders insoluble the bichromate of potash or other mineral substances
remaining in the same, and, moreover, strengthens and improve such leather by
filling up the pores of the same. Such gelatine, moreover, replaces the natural
gelatine which has been dissolved, to a greater or less extent, by the prior
treatment to which the skin or hide has been subjected.
Having thus fully described the said invention as communicated to me by my
foreign correspondent, and the manner of performing the same I wish it understood
that I claim
First. The combination of a vegetable tanning which superficially colours the
leather, and a mineral tanning which acts rapidly upon the whole thickness of the

page_text: leather and modifies the colour given by the vegetable tanning, in order to
economically obtain leather well tanned throughout its entire thickness, and coloured
by the vegetable substance, substantially as set forth.
Second. The tanned hides or skins obtained by the above described vegetable and
mineral tanning.
Third. The process of mineral tanning completed by the treatment with gelatine
or a like substance, which renders insoluble the said gelatine and the mineral
substances remaining in the skins or hides and strengthens and improves the
leather, substantially as set forth.
Fourth. The hides or skins tanned by the mineral tanning and improved and
strengthened by the treatment with the gelatine or like substance, substantially as
set forth.
Fifth. The process comprising the three successive operations of the vegetable
tanning, the mineral tanning and the treatment with gelatine, substantially as set
forth.
Sixth. The hides or skins produced by the above described operations, tho
nature of the substances employed, the composition of the bath, the duration of the
operation, the temperature, and other conditions, being varied as required.
In witness whereof I the said William Robert Lake have hereunto set my
hand and seal this nineteenth day of August in the year of Our Lord One
thousand eight hundred and eighty two.