AN IMPROVED METHOD OF TANNING SKINS AND HIDES
Year: 1882

page_text: LETTERS PATENT to Peter Jensen of 33 Chancery Lane in the County of
Middlesex for an Invention of AN IMPROVED METHOD OF TANNING SKINS
AND HIDES Communicated to him from abroad by Stavanger Aktie
Garveri of Stavanger Norway
"
PROVISIONAL SPECIFICATION left by the said Peter Jensen at the Office
of the Commissioners of Patents on the 13th December 1882.
PETER JENSEN of 33 Chancery Lane in the County of Middlesex
'AN IMPROVED
METHOD OF TANNING SKINS AND HIDES" (A Communication to me from abroad by
Stavanger Aktie-Garveri” of Stavanger Norway).
The object of the ordinary method of tanning is to render skins and hides strong
and waterproof.
This is usually attained by laying them in a solution of tannic acid which after a
long time combines with the substance of the hide.
This method of tanning has the inconvenience that it takes a very long time.
Of late years it has been tried to prepare leather by the help of certain mineral
materials. Certainly this is a quick way of attaining the object, but it is supposed
the leather so treated is not so strong. This invention consists in using both a
tannic and a mineral material simultaneously. Hereby is attained that the leather
receives as good a surface as the ordinary leather which is of great consequence for
the treatment later on and colouring of the leather and besides that it is rendered
strong throughout in a short time.
Catechu is preferably used as a tannic material still other materials containing
tannic acid may be used such as birch and oak bark, Sumach and the like.
The mineral material which is found to be most suitable is ordinary copper
vitriol, the soaking and softening treatment in lime and unhairing are done in the
usual manner. After the cleaning the sole leather with the lime contained therein
is put into the liquid. This latter is composed of catechu, copper vitriol and
enough sulphuric acid to keep the liquid acid, after the skins have been laid in it.

page_text: A weak solution is employed the first day but it is gradually increased in strength
in the course of a fortnight to three weeks when the copper vitriol has penetrated
the whole hide. Then the hide is laid in clean water for about a day to get rid
of the superfluous acid thereupon it receives a coating of a mixture of well boiled
linseed oil and resin. Hereby is obtained that the interior of the hide is covered
and protected against the air.
-
For tanning leather for uppers the lime must be removed as much as possible
and for this purpose muriatic acid is used instead of sulphuric acid.
After the tanning the leather is put into a decoction of birch bark for a day to
remove the superfluous acid, then it is washed out and blackened directly.
It is then greased and hung up until it is half dry, stretched grained, greased
again, well dried and finished in the ordinary way.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Peter Jensen in the Great Seal Patent Office on the 13th June
1883.
"
PETER JENSEN of 33 Chancery Lane in the County of Middlesex "AN IMPROVED
METHOD OF TANNING SKINS AND HIDES (a Communication to me from abroad by
Stavanger Aktie-Garveri of Stavanger Norway
The object of the ordinary method of tanning is to render skins and hides strong
and waterproof.
This is usually attained by laying them' in a,solution of tannic acid which after
a long time combines with the substance of the hide.
This method of tanning has the inconvenience that it takes a very long time.
Of late years it has been tried to prepare leather by means of certain mineral
materials. Certainly this is a quick way of attaining the object, but it is supposed .
the leather so treated is not so strong. This Invention consists in using both a
tannic and a mineral material simultaneously, and in the manner hereinafter
described
Hereby is attained that the leather receives as good a surface as the ordinary
leather, which is of great consequence for the treatment later on and coloring of
the leather, and besides that it is rendered strong throughout in a short time.
Catechu is preferably used as a tannic material, still other materials containing
tannic acid may be used such as birch and oak bark, Sumach, and the like..
The mineral material which is found to be most suitable is ordinary copper
vitriol. The soaking and softening treatment in lime and unhairing are done in
the usual manner. After the cleansing, the sole leather with the line contained
therein is put into the liquid This latter is composed of Catechu copper-vitriol
and enough sulphuric acid to keep the liquid acid after the skins have been laid in
it. A weak solution is employed the first day but it is gradually increased in
strength in the course of a fortnight to three weeks when the copper vitriol has
penetrated the whole hide.
As an example I will describe the usual mode of treatment of 100 hides for
making them into sole-leather. After the hides have been unhaired and freed from
fleshy parts and lime they are ready to be tanned. For this purpose I prepare a
solution consisting of 18 lbs birch bark 18 lbs copper vitriol 4 lbs "Glaubers" salt
and 88 lbs good catechu all mixed with water sufficient to dissolve these
ingredients. One third of this solution is now put in a vat with water; the vat
must be of such a size and capacity that the hides are covered by the liquid and can
be driven round easily. I also at this stage add /, lb sulphuric acid. The hides are
now driven round in this vat, 3 to 4 times daily. and after the third day the liquid in
the vat is raised to about 68 F.. Another one third of the solution is added about eight
days after together with 1/2 lb sulphuric acid. The hides are driven round 3 to 4
times each day and after the lapse of two to three weeks the rest of the solution is
added together with a strong tannic extract from birch bark and the hides being
driven round 3 to 4 times daily until they are "dressed" that is to say in the
course of 8 to 12 days. The hides are during the whole tanning process struck up
each day and the water is kept at the even temperature of 68 F The dressed
leather is put, in clean cold water for one or two days in order to get rid of the
superfluous acid and then rubbed over with a mixture of oil and resin 1 lb resin
to, gallon well boiled linseed oil. Hereby is obtained that the interior of the .
hide is covered and protected against the air.
The ingredients will vary slightly according to the nature of the various hides.
Thus for 100 goat skins we should use 9 lbs Copper Vitriol 66 lbs. Catechu and

page_text: 7 lbs salt. For thick and heavy hides which are to be applied for driving belts and
soles I use Glauber's salt but for other purposes I use common salt.
For tanning leather for "uppers", the lime must be removed as much as possible
and for this kind of leather muriatic acid is used instead of sulphuric acid. After
the tanning the leather is put into a decoction of birch-bark for a day in order to
remove the superfluous acid and it is then washed out and blackened directly. It
is then greased and hung up until it is half dry and is stretched, grained, greased
again, well dried and-finished in the ordinary, way.
And having thus described and ascertained the nature of this Invention as
communicated to me I declare that I claim the tanning process herein before
described having the destinctive feature of the employment of a solution of Catechu,
birch bark. copper vitriol, Glaubers salt; (or common salt) and sulphuric acid (or
muriatic acid) in such a manner that the strength of the solution is gradually
increased in the manner described and finally obtains an addition of strong tannic
extract from birch bark all substantially as described.
In witness whereof I the said Peter Jensen have hereunto set my hand and
seal this Twelfth day of June in the year of our Lord One thousand
eight hundred and eighty. three.
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