IMPROVEMENTS IN TANNING ALL ANIMAL SKINS
Year: 1868

page_text: LETTERS PATENT to Louis Clozel, of No. 6, Rue des Filles du
Calvaire, in the City of Paris, in the Empire of France, Medical
Doctor, for the Invention of "IMPROVEMENTS IN TANNING ALL ANIMAL
SKINS."
Sealed the 23rd March 1869, and dated the 14th October 1868.
PROVISIONAL SPECIFICATION left by the said Louis Clozel at the
Office of the Commissioners of Patents, with his Petition, on the
14th October 1868.
I, LOUIS CLOZEL, of No. 6, Rue des Filles du Calvaire, in the City of
Paris, in the Empire of France, Medical Doctor, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN TANNING ALL ANIMAL
SKINS," to be as follows:-
The two essential features of my Invention are,-
First, the substitution for the lime (ordinarily employed in preparing
skins for the removal of the hair) of caustic soda or potash, or
sulphuret of sodium, better known under the name of eau de javelle.

page_text: The quantity of soda or potash or sulphuret of sodium employed must
necessarily vary according to the nature of the skins, sulphuret of
potassium may also be used in solution. After the skins have remained
four or five days in the, solutions thus formed they are in a condition
for having the hair removed, having been previously steeped in a bath
containing from one to three parts of sulphuric acid, nitric acid, or
acetic acid.
Secondly, after the removal of the hair the skins are plunged into
baths containing animal or vegetable substances capable of a rapid and
specially putrid fermentation, but not alcoholic, acetic, or lactic as is the
case with the bran or other amylaceous baths at present employed.
I compose my baths of matters either in a state of putrifaction or
capable of rapidly becoming so; I generally employ urine either pure
or mixed with water, or I make use of meat, blood, or the water used
for hemp retting; under the influence of these baths the putrefaction
is communicated to the skins and they become softened, the fatty
matters saponifying by the action of the ammoniacal salts formed;
the skins are thus more readily cleansed and the labour is considerably
reduced.
Finally, the skins being sufficiently softened are placed in bran or
other amylaceous baths for dressing them, or instead of the bran bath
a solution of acetic acid and water may be used.
My method therefore consists in the use of the solutions of caustic
potash, soda, or other substances above described in lieu of the lime
ordinarily employed for removing the hair, and in the use of the putrid
fermentation baths not specially acid as herein-before mentioned.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Louis Clozel in the Great Seal Patent Office on the
7th April 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, LOUIS 30
CLOZEL, of No. 6, Rue des Filles du Calvaire, in the City of Paris, in the
Empire of France, Medical Doctor, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fourteenth day of October, in the

page_text: year of our Lord One thousand eight hundred and sixty-eight, in the
thirty-first year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Louis Clozel, Her special licence that
I, the said Louis Clozel, my executors, administrators, and assigns, or
such others as I, the said Louis Clozel, my executors, administrators,
and assigns, should at any time agree with, and no others, from time to
time and at all times thereafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend, within the
United Kingdom of Great Britain and Ireland, the Channel Islands,
and Isle of Man, an Invention for "IMPROVEMENTS IN TANNING ALL ANIMAL
SKINS," upon the condition (amongst others) that I, the said Louis
Clozel, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and seals, should particularly
describe and ascertain the nature of the said Invention, and in what
manner the same was to be performed, and cause the same to be filed
in the Great Seal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Louis Clozel, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement, that is to say :-
This Invention relates to a new method of tawing skins of animals,
or in other words in the manufacture and dressing of white leather.
In order to clearly show in what my Invention consists I will here
explain the old method. The skins after being steeped in pure water
for several days are plunged into a bath of lime either pure or mixed
with a little sulphide of ars or orpin, and after remaining therein for
some time they are withdrawn in a condition for shaving or having
the hair removed; after this latter operation they are again subjected
to a water bath in which they are turned about so as to remove as much
as possible all foreign matter; it is necessary that the water for this
purpose should be as pure as possible, and it is consequently frequently
changed. After the washing the skins are placed in bran baths and
after a time they are dressed, that is to say, they are steeped and
stirred about in a mixture of water, corn, the yolk of eggs, alum, and
sea salt; having now described the old principle, I will proceed to
mention the new, the first modification of which consists in tho

page_text: employment of caustic potash or soda, sulphuret of sodium, or
hypochlorite of potash or soda, known under the name of eau de javalle,
in place of the lime for preparing the skins for removing the hair.
It is impossible to indicate the precise quantities of the ingredients
alluded to, as they must necessarily vary according to the nature of
the skins to be operated on, nevertheless I commence always by
putting the skins in a solution of one of these substances in the
proportion of one-tenth part to one hundred pints of water; the potash
or soda which I prefer to employ is caustic, or I make use of a caustic
solution of the before mentioned substances, decarbonizing by means
of lime a solution of carbonate of potash, soda, or sulphate of sodium
according to the quantity of lime employed and in the proportions
indicated by the law of chemical equivalents. In the caustic solutions
thus formed and deprived of the carbonates of lime I plunge the skins,
and although this solution is the best it may be used without removing
the carbonate of lime formed or the excess of caustic lime. The skins
after remaining four or five days in this solution are in a condition for
having the hair removed, this is performed on leaving the solution,
having previously plunged them in a simple water bath containing
from one to three parts of sulphuric, nitric, chlorhydric, or acetic acid,
this latter operation facilitates the removal of the hair. Sulphuric acid
must not be used, as the other acids form solubles with the decomposed
lime and admit of the skins being more readily dressed when the hair
is removed. After leaving this water bath they are plunged in baths
containing animal or vegetable substances capable of a fermentation
rapid and specially putrid, but not alcoholic, acetic, or lactic, as I
compose my baths of matters in a state of putrefaction or vegetable or
animal substances capable of rapidly becoming so; I generally make
use of urine either pure or mixed with water according as I wish the
putrefaction of the skins to take place more or less rapidly, or instead
of urine I can employ meat, blood, or water used in hemp retting; this
decomposition is communicated to the skins, and they are softened and
supple, the fatty matters saponify by the action of the aminoniacal
salts and the skins are more readily cleansed, the labour being reduced
considerably. When the skins are sufficiently cleansed and softened,
I place them in a bran or other amylaceous bath after which they are
dressed, or in lieu of the simple bran bath I can employ in conjunction
a solution of water and acetic acid. The substitution of the caustic

page_text: potash or soda, or of the substances already referred to in place of the
lime, is of the utmost importance. As for example, the lime. is almost
insoluble, consequently its action is not uniform; moreover in saponifying
the fatty matters of the skns the lime forms lime soaps, sterates,
oleates, or margrates of lime almost insoluble, therefore it. is only by a
mechanical action that these elements can be removed from the skins,
and very frequently the lime remains in the form of caustic or carbonate
of lime, which renders the skin brittle, uneven, and of a bad colour.
The length of time the skins are kept in the lime greatly impairs them.
The substitution of the ingredients before alluded to in place of the
lime is therefore of the greatest importance whether as regards the
rapidity of manufacture or the quality of the skins. It is for these
reasons that I can plunge the skins as soon as they are ready to have
the hair removed into the putrid fermentation baths; if the hair had
been removed by lime they could not have borne them without a too
rapid change, as they would become eaten before they could be properly
cleansed. It is for this reason that the dressers are obliged to keep
the skins in water and in summer time it is necessary that the water
should be as pure and changed as often as possible.
Having discovered that the skins treated by the old method or water
bath system do not retain their suppleness unless by gentle fermentation,
such fermentation being less active when the water is not changed so
often, I conceived the idea of employing liquid putrefaction baths acting
in a regular and uniform manner on every part of the skin; by this means
the fatty matters become saponified, and the soaps consequently remain
in solution in the bath and the skins attain rapidly and retain their
suppleness after being dyed and the foreign matter is removed from the
skins by the fermentation, and the cleaning is effected more rapidly and
with less trouble.
Having thus described my Invention, what I claim is the employment
of caustic soda, or potash solutions or other substances as herein-before
explained for removing the hair, and the use of the putrid fermentation
baths, not acid, as well as the bran fermentation baths specially acid.
Amongst the advantages of my system over the old I may mention
the reduction in manual labour and in the cost of the manufacture, the
skins being more supple and taking and retaining a brilliant dye; the
time required for the manufacture is also reduced, whilst as regards

page_text: the instruments and apparatus the same as those at present in use are
employed.
In witness whereof I, the said Louis Clozel, have hereunto set my
hand and seal, this Third day of April, in the year of our Lord
One thousand eight hundred and sixty-nine.
LOUIS CLOZEL. (L.S.)