CERTAIN IMPROVED PROCESSES OF TANNING
Year: 1841

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN Cox,
of Gorgie Mills, Edinburgh, Tanner and Glue Maker, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Twenty-first day of December, in the Fifth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
John Cox, Her especial licence, full power, sole privilege and authority, that I,
the said John Cox, my exors, adññors, and assigns, or such others as I, the
said John Cox, my exors, adiñiors, or assigns, should at any time agree with,
and no others, from time to time and at all times during the term of years,
should and lawfully might make, use, exercise, and vend, within England,
Wales, and the Town of Berwick-upon-Tweed, my Invention of " CERTAIN
IMPROVED PROCESSES OF TANNING;" in which said Letters Patent is contained
a proviso that I, the said John Cox, shall cause a particular description of the
nature of my said Invention, and in what manner same is to be performed,
to be inrolled in Her said Majesty's High Court of Chancery within six
calendar months next and immediately after the date of the said in part,
recited Letters Patent, as in and by the same, reference being thereunto had,
will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
John Cox, do liereby declare the nature of my said Invention, and the manner

page_text: in which the same are to be performed, are fully described and ascertained in
and by the following statement thereof; that is to say:-
The nature of my Improved Processes of Tanning consists in superio
methods to any yet practised of the application of the principle of infiltration
or percolation, produced by hydrostatic pressure of tanning liquor through the
fibres and pores of hides and skins when formed into a bag, and also of
superior methods of causing alternate absorption and expression of liquor into
and out of the pores of hides and skins, and of increasing the action or effect
of endosmosis and exosmosis, and of softening, cleansing, and preparing hides
and skins for tanning or other process of leather manufacture, thereby saving
time, labor, and capital, and improving the quality of the leather. Various
have been the methods hitherto attempted or proposed to facilitate the tanning
of hides and skins by causing percolation of tanning liquor through their
pores, but these have been always attended with great inconvenience and
expence in the working, or the leather produced has been unequally tanned
and inferior in color and quality. The processes I am now about to describe
remedy more or less all these disadvantages.
After the hides and skins have been prepared in the usual way (as is well
understood), or by the assistance of my preparatory process (to be afterwards
described) for the tanning liquor, each is to be made into a bag, by carefully
sewing the corresponding edges of the different parts together with good pack
thread, so as to cause as little waste as possible of any part of the said hides
and skins; or more hides and skins than one, or only a part or parts thereof,
may be so formed into a bag, but in all cases leaving an aperture at any
convenient place by which the tanning liquor can be produced therein, and
taking care to sew or close up any holes that may otherwise exist in the hides
or skins, that they may contain the liquor the more securely. In this state of
bags they are in a condition to undergo or be submitted to any of four of my
improved processes of tanning; but, previous to commencing, it may be of
some advantage for color to handle them in liquor in the usual way for
a day or two.
My first improved process of tanning is, to take the hide or skin bag and
lay it upon a floor of wood or other suitable surfaces, and introduce into the
aperture in the said bag, left for the purpose, (which may be at the head,
shanks, or other convenient place), a rigid tube or a rigid nozzle, attached to a
flexible tube, and tie or fix the said bag at the said aperture tightly to the said
tube or nozzle, so as to prevent the escape of the tanning liquor from out of
the bag by the said aperture when liquor is introduced into the said bag.
The rigid or flexible tube is to be attached to or connected with a cistern or

page_text: vessel, of such depth or at such an elevation as will admit of hydraulic
pressure being exerted upon every part of the interior of the hide or skin bag
when the said cistern or vessel contains tanning liquor. Suppose that a full-
grown ox hide is taken to be operated upon, the diameter of which, when
sewed into a bag and filled with liquor, would be about two feet; I prefer
that the surface of the liquor in the cistern be at an elevation of about four
feet above the floor or surface on which the bags lay (which floor or surface
may be either hard or soft, porous or close, rigid or flexible), and by allowing
the liquor to flow from the cistern through the connecting tube into the bag
(which I prefer to lay in nearly a horizontal position), such bag will swell up
like a bladder filled with wind or water, and from the liquor in the cistern
being about two feet above the top level of the bag when swollen up with
liquor, there will be percolation or infiltration induced through every part.
thereof, at the upper surface as well as at the lower surface and sides, which
will speedily effect the tanning of the whole hide or skin without the necessity
of turning it from side to side, as has hitherto been necessary where hide or
skin bags have been merely filled with tanning liquor, without applying any
additional hydrostatic pressure, and when unconfined in any cage or rack,
and unconnected with a feeding cistern. If the feeding cistern be kept always
or generally or frequently full of liquor (say from twenty degrees to forty
degrees of strength), so as always or generally or frequently to keep the bag
fully distended or swollen, the process of tanning will be completed in a few
days. The hide or skin may lay either upon its side or back, as may be most
convenient for affixing it to the feeding tube or nozzle.
My second improved process of tanning is upon the same principle of
infiltration of liquor through the pores and fibres of hides and skius, but it is
better calculated than my first process to save space and quantity of liquor
requisite at a time, and prevent any over distension of the fibres. The hide or
skin being formed into a bag, as before mentioned, I confine or support it
within a narrow compartment or stall, say four inches (more or less) wide, and
sufficiently long and deep as fully to contain the said bag when free from folds
or wrinkles. It is necessary that the partitions forming the sides of the com-
partment or stall should be of an uniform continuous smooth surface, or nearly
so, and not racked or roughel, which has been found not to succeed) so that
the hide or skin sball not be injured or marked, or unequally turned from
unequal reaction or support to the hydrostatic pressure, but that the reaction
or support of the partitions shall be exactly equal to the hydrostatic pressure at
any given part of the hide or skin in contact with them. I prefer that the
partitions be made of wood, as smooth as possible, but which may be lined with

page_text: cloth or other porous substance if wished, which however is not necessary. The
liquor is to be supplied to the hide or skin bag in a manner exactly similar to
that described above as applicable to my first process, but greater altitude
may be given to the feeding cistern or liquor therein, as by confining the bag
within a compartment it is not apt to suffer from over distension. When the
liquor is introduced into the bag which is placed into the compartment, caro
must be taken to keep it free from wrinkles or folds by drawing it upwards and
lengthwise as it fills, so that the surface of the hide or skin may be pressed
uniformly and smoothly against the sides of the compartment. In turning in a
compartment I prefer that the belly of the hide or skin be placed uppermost,
and that the partitions of the compartment be placed vertically and parallel to
each other, and of such strength that they will not yield or give way by the
hydrostatic pressure they will have to support. When a series of compart-
ments are to be used in a row, the pressure from one hide or bag will counter-
balance that from the one next it, and thus render it unnecessary to use very
strong wood for the partitions. The partitions should rest upon a good floor,
to which they should be firmly fixed, and their tops or upper edges should be
bound together by bars of wood. More than one bag may be put into a com-
partment if care be taken to supply them nearly equal with liquor, and to
prevent them from being wrinkled as percolation goes on, although one hide be
in contact with or press against another.
My third process of tanning upon the principle of infiltration or percolation
is, to suspend the hide or skin by cords entirely or partially from off the ground
or floor. The hide or skin being thus formed into a bag, as before described,
I puncture holes through both plies or sides of the hide or skin, close to the
sewing of the belly, neck, and shanks, so that vertical lines drawn from them
will be about three inches apart. I then introduce through these holes cords
of sufficient strength to bear the weight, having a knot tied at one end which
cannot get through the holes; I then tie or fix these numerous cords to a bearer
or pole sufficiently strong to bear the necessary weight, so that the hide or
skin shall be suspended with the belly uppermost, and kept in as horizontal a
position as possible, so that nearly an equal weight may be sustained by each
cord. By introducing and fixing a tube or nozzle into the bag connected with
à cistern of liquor slightly elevated above the top level of it, it will fill and
swell out, and the liquor will percolate through every part of the hide or skin
without being obstructed by the contact of any rigid or porous substance what-
ever, and thus the tanning will speedily be effected. These three processes
now described are all to be conducted in the atmospheric air.
My fourth improved process of tanning by infiltration is still more perfect

page_text: than any of the other three above described, as it causes equal percolation or
equal effective pressure through or upon every part of the hide or skin, and
admits of said pressure being regulated to the greatest nicety and exactness,
from less than an ounce to several pounds per squaro inch, so as to produce
the most proper and equal degree of tension of the fibres of the hide or skin.
It is also the most convenient process, can be applied in existing tan yards,
improves the colour and quality of the leather, and causes less loss of tanning
principle by decomposition from exposure of hide and liquor to the air. This
process, then, is to cause percolation or infiltration of tanning liquor through the
fibres and pores of hides and skins, when sewn into bags, by means of hydro-
static pressure, when the hides or skins at the same time immersed in liquor.
The position in which I prefer to have the hide or skin (when formed
into a bag) when tanning according to this process, is perpendicular in the
direction of its length, but it may also be in any of the positions, or confined in
a compartment, as already described, with the addition that the hide or skin be
immersed or suspended in liquor. The pit or cistern into which the hide or
skin is to be immersed should be sufficiently deep to admit of its being totally
submerged in liquor without or merely touching the bottom. The manner
in which I prefer to tan, according to this process is, to sew up the hide or skin,
as before mentioned, but leaving the aperture for the introduction of liquor at
the head, into which I introduce and fix a rigid tube connected with a cistern
about two feet above the level of the pit. I do not, however, confine myself to
any given height for the feeding cistern or liquor therein to be, which may be
varied advantageously according to the strength of the hides or skins under
process, the strength of the liquor, or stage of tanning. The connecting tube
through which the liquor is to be introduced into the bag should be some
inches in diameter (four inches being suitable) so as to admit of a plunger or
rod being introduced into it occasionally to stir up the bark or sediment that
may lodge at the bottom parts. The hide or skin bag being tied tightly
at the neck end to the feeding tube (which tube should be long enough to
dip a little down amongst the liquor in the pit in which the bag is to be
immersed), tanning liquor is to be supplied to the feeding cistern, when the
bag will swell until it can contain no more liquor, when percolation will
commence and be continued with a vigour proportionately to the height of
the liquor in the feeding cistern above the liquor in the pit of immersion.
As the bag fills with liquor the pit (having been previously full) will overflow
(unless the liquor is supplied from the pit of immersion), and therefore a run-
way must be made for the liquor to flow to a reservoir, from which it may be
pumped or lifted again to the feeding cistern, and as the percolation goes on

page_text: the liquor will flow to the reservoir, again to be raised and circulated as
before. The hides or skins turned according to this process may also be con-
fined in compartments, or jammed against each other, for the sake of saving
room and quantity of liquor necessary at a time, as described as being prac-
ticable in the atmosphere; but I prefer that each bag should have ample
room for swelling out as far as its dimensions will permit, as the tanning goes
on rather more rapidly and equally in all the parts, while the tension generated
by the hydrostatic pressure is more equal, rendering the leather more equal in
texture and quality. In this process of tanning there is a double hydrostatic
pressure exerted, a greater which is exerted inside of the bag, and a lesser
which is exerted outside of the bag, and it is the surplus pressure (which is
equal at all parts of the bag) of the one above the other that causes the per-
colation of liquor from within outwards.
In all these four processes now
described, I prefer that the grain side of the hide or skin be outwards, though
I do not confine myself thereto, and I also prefer that some bark or other
solid tanning ingredient be introduced into the bags, so as to help to keep up
the strength of liquor, and to stop up any holes or apertures that may be in
the hide or skin. Although pits are not deep enough to admit of the total
immersion of the hides or skins, it is of no great consequence whether the
necks be above the liquor and thereby have rather less hydraulic pressure
upon them, provided there be as much pressure as to cause them to tan nearly
as quickly as the thickest part of the hide or skin. The gentle hydrostatic
pressure exerted inside of the hide or skin bag when tanning according to this
process improves the quality, as it consolidates the texture of the leather and
equalize its rigidity and elasticity, and thereby will save the currier and shoe-
maker considerable trouble in setting it out or beating it out to its natural
limits of extension. For belt hides for machinery the tension kept up during
the tanning will be of great benefit, as from every part being brought to an
equal degree of elasticity or rigidity, unequal stretching, twisting, or screwing
will be prevented after the belts are cut from the hides. By increasing the
hydrostatic pressure as the tanning progresses, the hide or skin will stretch
more nearly to its ultimate limits of tension, and being thoroughly tanned' in
that position, its capability of future tension will be greatly decreased.
When
the tanning is completed the sewing is to be opened or cut out to allow the
liquor to escape, or it may be run out by means of a syphon, by gently
elevating the hide or skin as the liquor is run off, after which it may be laid
away for a short time in a pit in the ordinary way to improve colour, or dried
and finished as usual, care being taken to free it of the pack thread that
may be adhering, and paring off any unseemly parts.

page_text: My fifth improved process of tanning is, to submit hides and skins fre-
quently to alternate greater and lesser hydrostatic pressure than has been
hitherto practised, by causing them to be frequently sunk and raised in tanning
liquor to and from a greater depth than usual. The general depth of tan pits
has heretofore been from five to seven feet, and therefore I do not claim the
using of such; but what I claim is, the improved method of tanning in pits
which shall contain liquor above ten feet in depth, or of greater depth than
has hitherto been usual, and I prefer that the depth shall be from thirty to a
hundred feet, as the deeper the liquor is the greater will be the hydrostatic
pressure at the bottom of the pit, and the more effective will the process of
tanning be. Provided with a pit of such unusual depth containing tanning
liquor, I prefer to conduct my process as follows:-I erect over the top or
in the pit a sparred reel or other suitable figure, which shall reach across the
whole breadth of the pit, and be of such strength as to bear the necessary
weight to be put upon it. I then form the hides or skins into endless belts
or bands of such dimensions as will reach to the depth wished, and place or
suspend them on or from the reel so that they shall dip or hang down into
the liquor. I continue to put one endless belt above another until the space
in the pit is sufficiently occupied, taking care that each belt shall be rather
larger than the one immediately under it, so that they may all circulate freely.
To keep the belts in their proper place, the reel should have side flanges or
guides, so that they may not rub against the supports. By giving suitable
rotatory motion to the reel, circulating motion will be communicated to the belts
of hides or skins hanging from or upon it, which will cause every part of said
belts to be gradually subjected to the hydrostatic pressure due from the depth
of immersion into the liquor contained in the pit; and as the circulation of the
belts proceeds, each hide or skin will be alternately subjected to increasing
pressure (as it descends in the liquor), and to decreasing pressure (as it ascends
in the liquor); and by this alternate sinking to and rising from a great depth
of immersion, alternate compression and expansion of the substance of the
hide or skin will be the consequence, thereby causing alternate absorption and
expression of liquor into and from the pores of said hides or skins, which will
promote or facilitate the tanning. If the hides or skins be not sufficiently
specifically heavy to sink easily in the liquor, weights may be attached to the
belts, or a reel may be placed near the bottom of the pit, around the under
side of which reel the belts may circulate, and there may be vertical partition
in the pit (leaving, however, a free space near the bottom for the turning or
revolving of the belts,) which would prevent the descending parts from coming
in contact with the ascending parts of the said belts.

page_text: My sixth improved process of tanning consists in the application of a
bleacher's common wash or dash wheel (being a closed cylindrical box or
drum divided into radial compartments, mostly four in number, with apertures
in the side to admit the goods, and an axis through the centre on which to
revolve), the dimensions of which I prefer to be seven feet in diameter and
three feet in breadth, and into which I place the hides and skins to be tanned,
and supply them with tanning liquor. I prefer that the dash wheel revolvo
into or above a cistern containing tan liquor, and that the liquor be supplied
to the inside of the wheel by means of a pump throwing it on the circum-
ference of the wheel, in which are holes for its admittance, or it may be
injected at the side or otherwise. Motion being given to the wheel in any
convenient way and at any convenient speed, the bides or skins will be jolted
and knocked and turned about, so as to promote the tanning. The principle
upon which this process depends is that of momentum and compression. When
a bide or skin is jolted, or its velocity or motion suddenly checked, or stopped,
or changed, the solid particles are compressed against each other, causing a
closer texture for the moment, thereby forcing some liquid from the interstices
or pores, and thereby creating a fresh capacity for absorbing fresh liquor. And
as the momentum of liquids is not so suddenly checked as that of solids, the
liquid contained in the pores or interstices continue in motion when that of the
solid particles is checked, whereby a circulation of liquid in the pores and in-
terstices is the consequence. The effect from compression is further produced by
the weight or gravitation of the hides and skins upon each other. By subjecting
the hides or skins to the operation of the wheel for an hour (more or less) daily,
and letting them lay the remainder of the day in good liquor, the tanning of thick
hides may be effected in a few weeks. I find also that it saves labor, and is
otherwise advantageous to use this wash wheel for softening, cleansing, and
preparing hides and skins for tanning or other process of leather manufacture.
Hides for sole leather are sufficiently cleansed from lime and dirt by one opera-
tion in the wheel, which, with a good supply of water, will cleanse them in an
hour or two. Dressing leather may be subjected to the influence of the wash
wheel every time the hides or skins require working upon the beam, and dried
hides and skins may be softened in it previous to being put into the lime, it
being always advantageous to supply plenty of water, either cold or slightly
warm, to the interior of the wheel, which promotes the beneficial effects.
An experienced workman will easily sce on cach occasion when the hides and
skins have been sufficiently subjected to the action of the wheel, the time
depending on the speed, quantity of hides or skins in the wheel, and supply of
liquor given. Leather for dressing, after being tanned, may be subjected to

page_text: the influence of the wheel as a substitute for scouring, thereby saving labor to
the currier by the loose tan and bloom being discharged, and the leather
softened. In the construction of the wheel for tanning, care must be taken to
keep all iron bolts and nails beyond the reach of the liquor to prevent staining
or discoloration of the leather.
Ilaving thus stated the nature of my improved methods of tanning, and the
manner of carrying the same into effect, I would have it understood that I do
not claim the principle of tanning hides or skins by causing percolation of
liquor by hydrostatic pressure through their pores and fibres, nor the sewing of
hides and skins into bags, nor simply filling them with liquor when unconnected
with a feeding cistern, and without causing additional hydrostatic pressure,
nor forming hides and skins into endless belts; but I do claim the peculiar
methods of tanning by hydrostatic and mechanical pressure, momentum, and
otherwise, as described.
First, I claim the tanning of hides and skins by means of hydrostatic
pressure, when a cistern or tank or liquor therein is kept above the level of the
said hides and skins when sewed into bags and connected with the said cistern
or tank by a tube or pipe, and when said bags are allowed to expand or swell
to their natural dimensions when lying on a suitable floor or surface when
unconfined or unsupported by any racked cage or frame, and when such hides
or skins are not turned from side to side to cause and equalize the tanning, as
has hitherto been necessary when no additional hydrostatic pressure was exerted,
and when they are not laced into a porous bag for support, and to assist the
percolation. And I further claim the mode of supplying tanning liquor to a
hide or skin bag by means of a rigid or flexible tube or pipe fixed thereto, and
connected with a tank or cistern, whether such tank or cistern be elevated
to such a height as admit of the said bag being filled fully or partially with
liquor, when said bag lays free or unconfined on a floor or surface.
Secondly, I claim tanning hides and skins by hydrostatic pressure when
formed into bags,' when they are confined or supported or suspended into
continuous smooth-sided narrow compartments or stalls, as described.
Thirdly, I claim tanning by hydrostatic pressure when a hide or skin is
formed into a bag, and totally or partially suspended from off the ground or
floor by means of cords, as described.
Fourthly, I claim the tanning by hydrostatic pressure when a hide or skin
is formed into a bag and immersed totally or partially into liquor, and either
confined in a continuous smooth-sided compartment, or allowed to expand or
swell to its natural dimensions without confinement, or jammed against other
hides and skins, as described.

page_text: Fifthly, I claim the method or manner of tanning hides or skins by
frequently subjecting them, when formed into belts, to alternate greater and
lesser hydrostatic pressure, produced by alternately and frequently immersing
them to and raising them from a greater depth of tanning liquor than has
hitherto been practised. I do not, however, claim the use of reels or other
suitable figure, or the forming of hides and skins into endless belts when
unconfined with deep pits; but I claim the putting of one or more endless
belt or belts above or over another, and causing them to circulate or have
motion all at once in the same pit, thereby saving and economising space and
liquor to a greater degree than has been yet practised.
Sixthly and lastly, I claim the tanning of bides and skins by introducing
them into a machine called or known by bleachers as the "wash" or "dash
wheel," and causing a frequent change of liquor to be supplied to them while
kept in motion in the wheel, and cleansing, working, and softening hides
or skins previous to being dressed into leather, and also for cleansing and
scouring tanned dressing leather, so as to save manual labour, and render the
leather soft and pliant.
In witness whereof, I, the said John Cox, have hereunto set my hand
Inrolled the Twenty-first day of June, in the year of our Lord One
thousand eight hundred and forty-two.