IMPROVEMENTS IN THE MANUFACTURE OF GELATINE
Year: 1852

page_text: LETTERS PATENT to Theophilus Redwood, of Montagu Street,
Russell Square, London, for the Invention of "IMPROVEMENTS IN
THE MANUFACTURE OF GELATINE."
Sealed the 30th March 1853, and dated the 2nd October 1852.
PROVISIONAL SPECIFICATION left by the said Theophilus Redwood
at the Office of the Commissioners of Patents, with his Petition,
on the 2nd October 1852.
I, THEOPHILUS REDWOOD, of Montague St., Russell Sqr, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN THE
MANUFACTURE OF GELATINE" to be as follows:-
The first part of my Invention consists in the treating of skins
or pieces of skins with acid phosphate of lime or a mixture of acid
phosphate of lime and charcoal. 1 usually prepare this mixture
by adding oil of vitriol to animal charcoal, diluting it with water.
The skins are put into this mixture and left there for a day or two.
They are then removed from the acid phosphate and put into lime
water, where they are left until the acid acquired from the previous
mixture has been completely neutralized. They are afterwards put
into water, through which carbonic acid gas is passed, so as to
neutralize and remove excess of lime.

page_text: The second part of my process consists in splitting the skins by
passing knife through the middle parallel with the surface or
cuticle, and turning the two pieces thus produced so that what
were the outer surfaces are brought together, and the newly cut
surfaces are turned outwards. The object of this part of the pro-
cess is to protect the cuticle or outer skin from the solvent action
of the water to which the skins are subsequently exposed. When
the skins are thin, instead of splitting them, I merely place two pieces
together in such a manner that the surfaces from which the hair
has been removed are opposed to each other. The picces are fixed
in this position by placing them between frames of open wirework
by which they are pressed together. The most impure part of the
skin is thus placed inside, where it will not be acted upon in its sub-
sequent treatment.
The third and last part of my Invention consists in submitting the
skin pieces in their frames to the direct action of steam under pressure,
which is effected by putting them into a closed vessel, and allowing
high pressure steam to enter. After this hot water is allowed to run
into the vocal by which the relatine is dissolved.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Theophilus Redwood in the Great Seal Patent
Office, on the 2nd April 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
THEOPHILUS REDWOOD, of Montague Street, Russell Square, London,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Second day of October, in the year
of our Lord One thousand eight hundred and fifty-two, in the six-
teenth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Theophilus Redwood, Her special
licence that I, the said Theophilus Redwood, my executors, adminis-
trators, and assigns, or such others as I, the said Theophilus Redwood,
my executors, administrators, and assigns, should at any time agree

page_text: with, and no others, from time to time and at all times there-
after 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 In-
vention for "IMPROVEMENTS IN THE MANUFACTURE OF GELATINE," upon
the condition (amongst others) that I, the said Theophilus Redwood,
by an instrument in writing under my hand and seal, should par-
ticularly 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 Theophilus Redwood, do hereby
declare the nature of iny 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):
My Invention has for its object the obtaining from skins and hides
gelatine of
pure quality and free from color, and in larger quantities than
has heretofore been obtained of pure quality, and free from color, and con-
sists in the treating of skins or pieces of skins as herein-after particularly
described; for this purpose I first treat the skins or pieces of skins with
acid phosphate of lime, or a mixture of acid phosphate of lime and char-
coal, and with lime water and carbonic acid. The acid phosphate of lime
may be made by adding one part of oil of vitriol mixed with twice its
weight of water to two parts by weight of common bone ash, allowing
the ingredients to macerate together for twenty-four hours, and then
diluting them with twenty parts of water; and the mixture of acid
phosphate of lime and charcoal may be made by substituting in this
process coarsely granulated animal charcoal for the common bone ash.
I prefer the mixture made with animal charcoal as being the most
efficaceous. The skins or pieces of skins, from which the air has been
removed in the usual way, are put into this mixture, and left there for a
day or two, or until the acid solution has penetrated through them.
The time required for this process will depend on the thickness and
closeness of texture of the skins. The skins are then removed from
the acid phosphate, washed with water, and put into line water, where

page_text: they are left until the acid acquired from the previous mixture has
been completely neutralized. The best mode of discovering whether this
result has been attained is to cut into the middle of the thickest pieces
of skin, and to apply there a piece of blue litmus paper which will be
reddened if any free acid still remains. The skins on being removed
from the lime water are washed with water and exposed to the
action of carbonic acid until the excess of lime acquired from the lime
water has been converted into carbonate of lime. I usually effect this
object in the following way:-The skins or skin pieces are first put into
a closed wooden vessel, which is kept filled with carbonic acid gas sup-
plied to it from an apparatus in which the gus is generated, and left
there for about twenty-four hours. They are then put into water con-
tained in another vessel, and carbonic acid gas is made to pass through
the liquid, by which means the carbonate of lime is dissolved, and thus
removed from the skins. After having been thus treated the skins
yield gelatine of a purer quality and with less color than that produced
by the ordinary process.
The skin so treated is subject to the next part of the process,
which has for its object the protecting the cuticle or other impure
surface of skin from the solvent action of the water used for dissolving
the gelatine, the grain side or cuticle of the skin and the flesh side
containing impurities, and not yielding so good a quality of gelatine
as the interior portion, and if taken up by tho water used to dissolve
the gelatine they injure the quality of the latter. To prevent as much
as possible these impurer parts being acted upon or dissolved in the
subsequent treatment to which the skins are subjected I proceed as
follows-When the skins or pieces of skins are of considerable thick-
ness they are split by passing a knife through the middle parallel with
the surface or cuticle, and the pieces thus produced are turned so that
what were the outer surfaces are brought together, and the newly
cut surfaces are turned outwards. The process of splitting is per-
formed with a splitting machine, such as is commonly used for
splitting skins. When the skins are thin, instead of splitting them, the
under surface or flesh side is scraped or shaved with a knife,
so as completely to remove all flosh, fat, and dirt, and then two

page_text: pieces are placed together in such a manner that the cuticles or
surfaces from which the hair has been removed are opposed to each
other, and brought into contact, while the scraped or shaved surfaces are
turned outwards. The splitting and turning the skins affords the most
easy and economical means of accomplishing the object contemplated,
but this cannot be advantageously adopted with thin skins, as in such
cases the newly cut surfaces would be too near the cuticle or impure
part to admit of the gelatine being dissolved from the exposed surfaces
without some of the impure parts being at the same time taken up, and
thus contaminating the gelatine. The skin pieces, which I prefer to be
of large size, are fixed with their surfaces placed, as described, between
frames of open wire work, by which or other similar means they are
pressed together, so that the most impure parts of the skin are retained
in the middle between the frames, and are thus in a great measure
protected from the solvent action of the water subsequently used. The
same object may be attained by placing a metallic plate or other hard
substance between the impure surfaces of the split or shaved skin, and
fixing them in that position by tying them with string or other similar
means.
The third and last process consists in submitting the skin pieces
in their frames to the direct action of steam under pressure, by
which the fibrous tissue of the skin is quickly converted into gelatine,
which may be dissolved by hot water. This is effected by putting the
frames between which the skins are contained into closed vessels
or steamers, the covers of which are securely fastened down so
as to confine the steam, and then allowing high pressure steam
to enter. These vessels should be strongly made, and are similar
to what are well known as digesters. The frames aro placed hori-
zontally in the steamers, as many being put onc over the other
in each vessel as will nearly fill it. Each set of two frames with
the skins between them are kept at a distance of half an inch from
those next to them by projecting bars or pieces of metal, so that
the steam can pass into this space, and come into contact with the
exposed surfaces of the skins. I usually employ steam at a pressure of
from ten to fifteen pounds to the square inch above the atmospheric

page_text: pressure, and allow the steam to remain in contact with the skins for
about half an hour. The tissues of the skin are thus converted into
gelatine much more quickly and completely than they would be by
boiling them in the usual way with water. The steam is now turned
off, and hot water at a temperature about the same as or not exceeding
that of the steam previously applied is allowed to run into the vessel,
by which means the gelatine is dissolved from the exposed surfaces of
the skins, while the cuticle or other part of the skins situated in the
middle between the frames remains undissolved. As it is important
not to allow the solvent action of the water to extend to the cuticle or
those parts which are impure, it is desirable that the steam should not
be kept in contact with the skins for more than half an hour before
introducing the hot water, and that the latter be applied for not more
than half an hour. If the pieces of skin are thin they might become
entirely dissolved or disintegrated; on this account, therefore, I prefer
to use large and thick pieces of skin which admit of a considerable
quantity of gelatine being dissolved from the pure and exposed surfaces
before coming to the cuticle or impure part. I find it advantageous in
conducting this part of the process to have two or more of the steamers
connected together by pipes; and having charged them with the skins, and
submitted the latter to the action of the steam, I introduce hot water,
first, into one of the vessels, and after allowing it to remain there ten or
fifteen minutes the solution thus formed is allowed to run into another
of the vessels, whence it may be transferred to others in succession until
it has become sufficiently charged with gelatine to form a very firm jelly
on cooling. A highly concentrated and pure solution of gelatine may
thus be obtained. After getting this first solution, steam may be again
admitted into the vessels for five or ten minutes, and a further portion of
gelatine may now be obtained by using hot water as before. If the
skins be of sufficient thickness, this second quantity of gelatine may be
as good as the first, but if in obtaining it the water should have pene-
trated near the cuticle of the skins the product would be of inferior
quality. By repeating the action of the steam and hot water, or of the
water alone, if the steam has been used for a sufficient length of time
to completely gelatinize the tissues of the skin, the whole or nearly

page_text: the whole of the gelatigenous portion of the skin may be obtained in
the form of solution of gelatine, while the cuticle is left in a thin film
between the frames.
Having thus explained the different parts of the process as parti-
cularly applied by me in the manufacture of gelatine, I wish it to
be understood that I do not claim the exclusive use of the several
above-mentioned processes, except as they may be employed in and for
the manufacture of gelatine as herein-before described. But I claim
as of my Invention the manufacture of gelatine by treating hides or
skins with acid phosphate of lime, or a mixture of acid phosphate of
lime and charcoal, lime water, and carbonic acid, placing the split or
scraped pieces with their outer surfaces in contact with each other, or
with a metallic plate or other hard substance, and subjecting the pieces
so placed to the action of steam under pressure and hot water, as above
described.
In witness whereof, I, the said Theophilus Redwood, have and
seal, this Second day of April, One thousand eight hundred
and fifty-three.
THEOPHILUS (L.S.) REDWOOD.