AN IMPROVED PROCESS OF TANNING
Year: 1864

page_text: LETTERS PATENT to François Pfanhauser, of Winsley Street, in the
County of Middlesex, for the Invention of "AN IMPROVED PROCESS OF
TANNING."
Sealed the 17th January 1865, and dated the 23rd November 1864.
COMPLETE SPECIFICATION filed by the said François Pfanhauser at the
Office of the Commissioners of Patents, with his Petition and Declaration,
on the 23rd November 1864, pursuant to the 9th Section of the Patent
Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FRANÇOIS
PPANHAUSER, of Winsley Street in the County of Middlesex, send greeting.
WHEREAS I am in possession of an Invention for "AN IMPROVED PROCESS
OF TANNING," and have petitioned Her Majesty to grant unto me, my executors,
administrators, and assigns, Her Royal Letters Patent for the same, and
have made solemn Declaration that I believe myself to be the true and first
Inventor thereof.
NOW KNOW YE, that I, the said François Pfanhauser, do hereby
declare that the following Complete Specification under my hand and seal
fully describes and ascertains the nature of my said Invention, and the manner
in which the same is to be performed, that is to say:-
The preliminary preparation of the hides, whether fresh, dry, or salted, to
render them suitable for immersion in the tanpit is precisely the same as

page_text: hitherto practised. When the calf skins or ox hides are freed from hair, well
cleaned, and washed, they are placed in the tan pit or vat, the best manner of
doing so being to suspend them.
The substance which in my improved process replaces oak bark or other
tannin is obtained by transforming sulphate of iron by means of a chemical
operation, furnishing a solution possessing the property of tanning the stoutest
hides in a few days.
The transformation of the nature of the sulphate of iron is very simple, and
is effected by burning it in an oven on a cast-iron platform heated from
beneath until red hot, and the substance being constantly moved about becomes
transformed into a powder of a reddish colour, when it is removed and the
operation repeated for a fresh supply.
The liquid is obtained by pouring water into an earthenware vase or other
suitable receptacle, then adding a part of the substance obtained as above
described, which rapidly dissolves if continually stirred with a stick or ladle,
the liquid is then allowed to rest and deposit until perfectly limpid, when it is
run off. This liquid being very strong serves to prepare the liquid in the tan
pits or vats according to the degree of strength which it is desired to give it,
using for this purpose Baumé's hydrometer or any hydrometer which the
tanner may prefer.
It is advisable to commence the operation of tanning by immersing the
hides, firstly, in a very weak solution, and to pass them by degrees to a
stronger, as, for example,―
The first day give to the solution but half a degree ("Baumé,") and when
the hides have remained therein during twenty-four hours remove them,
wash them well in pure water, and pass them into a solution of one degree
(Baumé); the third day into a solution of one and a half degrees; the fourth
day into a solution of two degrees; the fifth day into a solution of two and a
half degrees; the sixth day into a solution of three degrees; the seventh day
into a solution of four degrees; the eighth day into a solution of five degrees;
and if on the ninth day the hides are not yet well tanned and fit for removal
leave them for another day or two in a solution of the same strength, taking
care to add to the solution as much strength as the hides have absorbed, unless
to accelerate the operation it be preferred to increase the strength to six
degrees, which could not be hurtful.
When the hides are perfectly tanned throw them into water, and having
well washed them with brushes and pressed out as much of the tannin as
possible, leave them for twenty-four hours in pure water, and after another
washing and pressing immerse them in a slight solution of soft soap during

page_text: half a day, often moving them about, then well wash them again in this same
bath and suspend them for drying.
Having now described the nature of my said Invention, and the manner in
which I carry the same into practical effect, I would have it distinctly under-
stood that I do not confine myself to any precise strength of solution, or
precisely to the several operations above set forth, as such may be varied and
modified without departure from my improved process of tanning by means of
sulphate of iron treated substantially as herein-before described, and that I
claim the exclusive application of sulphate of iron so prepared to the tanning
of hides of every description.
In witness whereof, I, the said François Pfanhauser, have hereunto set
my hand and seal, this Twenty-third day of November, in the year of
our Lord One thousand eight hundred and sixty-four.
FRANCOIS PFANHAUSER. (L.S.)