IMPROVEMENTS IN THE PRODUC- TION OF PRINTING SURFACES BY PHOTOGRAPHIC AGENCY, AND IN OBTAINING PRINTS THEREFROM
Year: 1865

page_text: LETTERS PATENT to Joseph Wilson Swan, of Gateshead, in the County of
Durham, Chemist, for the Invention of "IMPROVEMENTS IN THE PRODUC-
TION OF PRINTING SURFACES BY PHOTOGRAPHIC AGENCY, AND IN OBTAINING
PRINTS THEREFROM."
Sealed. the 2nd January 1866, and dated the 6th July 1865.
PROVISIONAL SPECIFICATION left by the said Joseph Wilson Swan
at the Office of the Commissioners of Patents, with his Petition, on the
6th July 1865.
I, JOSEPH WILSON SWAN, of Gateshead, in the County of Durham, Chemist,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
THE PRODUCTION OF PRINTING SURFACES BY PHOTOGRAPHIC AGENCY, AND IN
OBTAINING PRINTS THEREFROM," to be as follows:-
My Invention consists of improved modes of producing by means of light
engraved plates, typographic blocks, lithographic or zincographic printing
surfaces, and of improved inodes of printing from the same, whereby I obtain
prints possessing more perfect gradation of light and shade than has hitherto
been secured by means of photographically produced plates, blocks, or other
printing surfaces.

page_text: To produce a photographically engraved plate adapted to a style of
printing which I afterwards describe under the denomination of "photo-
mezzotint printing," I proceed as follows:-I produce au image in gelatine,
and colour as described in the Specification of my Patent dated Feby. 29th,
1864, No. 503, mounting the tissue previous to development upon a surface
of slate or other suitable material; after development I surround the image
with a wall or border, and then act upon the image with a solution of a proto-
salt of iron, or with alum, or other suitable substance, with a view to prevent
the gelatine image from swelling in the electrotyping solution. I afterwards
produce a coating of silver upon the image, or otherwise render its surface
electrically conductible, and I then take an electrotype cast of it in copper.
After the removal of the electrotype cast from the vat, in order to strengthen
it, I fill in upon the back with plaster of Paris or other cement to the level of
the top of the border or wall. I use the electrotype cast produced as above
described for what I term " photo-mezzotint printing," which is performed as
follows:-I grease the surface of the engraved plate by means of a stiff brush
or in any convenient manner; I then pour on it a small quantity of slightly
warm gelatinous ink, composed of water, gelatine, and china ink, or other
suitable colouring matter; I place a piece of paper over this, and then apply
an even pressure to the back of the paper in such a manner as to cause the
gelatinous ink to spread over the entire surface of the plate, fill up all its
recesses, and cause the excess of ink (over and above what is required to fill
up the recesses to the level surface of the plate) to be squeezed out from
between the under surface of the paper and the highest points or level surface
of the engraved plate; I maintain the pressure until the solidification of the
ink, and then carefully remove the paper, which carries with it the print. Before
applying the paper, I generally prepare its surface by coating it with collodion>
albumen, or gelatine, with a view to prevent the discoloration of the paper in the
high lights. The press which I prefer to use is provided with a thin and elastic
plate of metal.
In the act of taking an impression the elastic plate is bent
so that it comes in contact with the back of the paper at one end, or across
the middle, and by being gradually straightened its pressure extends over the
entire surface required to be pressed, and the excess of the gelatinous ink is
thus easily and effectually displaced from the lights of the print. After
printing I subject the impression to the action of alum or other chemical
agent capable of rendering the image less liable to the softening action of
moisture.
To produce a photographically engraved plate adapted to ordinary" copper-
plate printing," and capable of rendering inversely in graduated tints the light,

page_text: י
shade, and half tone of an ordinary photographic negative, I proceed in the
same manner as has been already described for the production of plates for
the "photo-mezzotint printing," with this difference, that in this case I
guard against the removal of the printing ink from the recesses of the plate
in the act of wiping. I do this by forming in the recesses numerous extremely
thin walls, the tops of which are in the same plane as the unengraved surface
of the plate. The walls may be either in one series of parallel and equidistant
lines, or in two or more series intersecting each other. The single series of
walls gives to the recesses of the plate a trenched structure, while two or more
series give them a cellular structure. Where the trenched or cellular structure
of the recesses is objectionable I give them ink-holding capacity by studding
them with numerous slender spikes or bristles, the tops of which are in the
same plane as the unengraved portion of the plate. To produce a plate with
the trenched, cellular, or spiked recesses, ' form in or upon the negative of
the object to be engraved numerous opaque lines or dots, extending over its
entire surface, the lines or dots being equidistant, or nearly so; or I produce
the said lines or dots in the film of collodion, upon which the sensitive
gelatinous tissue is formed. I obtain the opaque lines by taking (in the
ordinary way) a photographic negative of a plate of glass coated with an
opaque etching ground, and with the required series of lines drawn upon it
with a point cutting through the etching ground to the surface of the glass.
The lines are cut closer or more open, as may be deemed necessary for the
kiud of work to be done, and the amount of reduction to be made in the size
of the negative obtained from them. I obtain the opaque dots by taking (in
the ordinary way) a photographic negative of a dark screen perforated with
numerous minute holes, equidistant, or nearly so; or I sometimes obtain the
dots by means of fine particles of some pulverulent opaque matter, either
dusted upon the negative of the object to be engraved previous to its removal
from the glass by means of gelatine in the well known manner used for
transferring negatives froin glass, or I diffuse fine particles of some opaque
pulverulent matter through a solution of gelatine, and apply a coating of this
to the negative previous to its removal from the glass. In all those cases
where the negative has had fine particles of opaque pulverulent matter applied
to it, I remove such negative from the glass on which it was formed, and in
using it I place its smooth or non-gelatinised surface in contact with the
sensitive gelatinous tissue in the act of exposure to light in the photographic
printing frame. In this exposure to light I arrange the printing frame so
that the rays of light may fall upon and enter the sensitive tissue perpen-
dicularly to its surface. After exposing the tissue in the printing frame I

page_text: mount it upon a smooth surface, and for this purpose I prefer slate. I then
develop with warm water, and treat with a solution of alum or a protosalt of
iron. I next render the image electrically conductible, and submit it to the
electrotyping process, performing these operations in the manner stated in
describing my mode of producing plates for photo-mezzotint printing. I use
the plate produced as above described in the ordinary manner of a copper-
plate engraving. When necessary 1 modify the ink used in printing from
such plate by reducing its colorific power and opacity, so as to obtain a print
possessing gradation of light and shade proportional to the different depths of
the recesses of the engraved plate.
That part of my Invention which relates to typographic and lithographic
printing consists chiefly in the production of what I terma crayon photograph,
that is to say, a photographic image in which gradation shade is produced by
dots of coloring matter more or less aggregated in proportion as the shading
is darker or lighter, and therefore corresponding to a crayon drawing in the
principle on which the gradation of shade is produced. Gradation of shade
in an ordinary photograph is continuous, and is produced by thicker or thinner
strata of semi-opaque colouring matter. Surface printing is not capable of
rendering this kind of gradation of shading, but it can give the granular or
dotted gradation which characterizes the crayon drawing, and I therefore
convert by photographic means the continuous gradation, such as an ordinary
photograph possesses, into the granular gradation, similar to that of a crayon
drawing. I produce the crayon photograph as above described in the following
manner: I make a solution of gelatine, and add to it an alkaline bichromate,
and also a certain proportion of charcoal or other opaque substance in such a
state of division or granulation that when diffused through the gelatine solu-
tion, and spread upon glass in a thin layer, the opaque particles will show
distinct granularity and interstices between particle and particle. In using the
above-described gelatinous solution I spread it upon a level surface of glassor
other suitable substance previously prepared with ox gall, or otherwise, to
facilitate the subsequent removal of the gelatinous sheet. I place the
gelatinised surface in a suitable position for quick drying, and guard it from the
action of injurious light; when the gelatinous coating is dry I coat it with
collodion, india-rubber solution, or other suitable film-producing substance, and
again dry; I then separate the gelatinous sheet from the glass plate or other
surface employed in its formation, and I place it in a photographic printing
frame beneath an ordinary photographic negative or positive of the object to
be printed. In doing this I put that surface which was uppermost during the
solidification of the gelatinous solution next to the negative or positive plate,

page_text: I then expose the printing frame to light in the usual manner, but I take
care that the light falls on the plate as nearly as possible perpendicularly to
its plane. After exposure to light I remove the photograpically impressed
gelatine sheet from the printing frame, and cement it with its impressed
surface downward upon a plate of glass or other suitable material; the
cement I prefer to use is a solution of india-rubber and gum dammar in
benzole. After mounting the gelatine sheet as described I subject it to the
action of warm water so as to dissolve away those portions of the gelatine
that have not been rendered insoluble by the action of the light which obtained
access to it while exposed under the negative or positive plate; I then coat
the gelatine image with a clear solution of gelatine, and after allowing it to
dry I separate the image from the glass, using ifnecessary benzole to facilitate
the separation. I thus obtain an image consisting of different thicknesses of
gelatine corresponding to the different degrees of lightand shade of the plate.
The gelatine having granules of opaque matter diffused through it, which
when viewed by transmitted light appear more or less aggregated in propor-
tion to the varying thickness of the gelatine. Having produced the crayon
photograph in the manner above described, I employ itinstead of an ordinary
negative or positive photograph in any of the well-known processes of photo-
typography, photo-lithography, or photo-zincography.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Joseph Wilson Swan in the Great Seal Patent Office on
the 6th January 1866.
TO ALL TO WHOM THESE PRESENTS SHALL COME, J, JOSEPH
WILSON SWAN, of Gateshead, in the County of Durham, Chemist, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Sixth day of July, in the year of our Lord
One thousand eight hundred and sixty-five, in the twenty-ninth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Joseph Wilson Swan, Her special licence that I, the said Joseph
Wilson Swan, my executors, administrators, and assigns, or such others as
I, the said Joseph Wilson Swan, my executors, administrators, and assigns,
should at any time agree with, and no others, from time to time and at all
time thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great Britain and

page_text: Ireland, the Chaunel Islands, and Isle of Man, an Invention for "IMPROVE.
MENTS IN THE PRODUCTION OF PRINTING SURFACES BY PHOTOGRAPHIC AGENCY,
AND IN OBTAINING PRINTS THEREPROM," upon the condition (amongst others) that
T, the said Joseph Wilson Swan, 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 mauner 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 Joseph Wilson Swan, 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) :-
My Invention relates to improved modes of producing by means of light
sunken or raised printing surfaces, and also lithographic or zincographic
printing surfaces, and also to an improved mode of printing from sunken or
intaglio printing surfaces. By means of this Invention I obtain, amongst
other advantages hereafter noted, prints possessing more perfect gradation of
light and shade than has hitherto been secured by means of photographically
produced plates, blocks, or other printing surfaces.
To produce a photographically engraved plate adapted to a style of printing
which I afterwards describe under the denomination of photo-mezzotint
printing, I proceed as follows:-I produce an image by means of bichromated
gelatine and coloring matter as described in the Specification of my
Patent
dated February Twenty-ninth, One thousand eight hundred and sixty-four,
No. 503. In applying the process described in the Patent referred to for the
purpose now contemplated I obtain, amongst other advantages, that of
governing the depth of the lights, penetration into the film of sensitive gelatine,
as a consequence of the mixture of a pigment or coloring matter with the
gelatinous solution from which the sensitive film is produced. For the present
purpose I mount the gelatinous tissue after it has received the actinic impres-
sion, and previous to its developement (as described in the above-mentioned
Patent) upon a surface of slate, glass, or other suitable material. Or instead
of producing the actinic impression upon the gelatinous tissue, and by means
of the superposition of a negative, as described in the Patent referred to, I
produce it by means of the camera, and in this case I do not use the tissue
described in my Patent of February Twenty-ninth, One thousand eighthundred
and sixty-four, No. 503, but instead of it I employ a plate of glass coated on
one of its surfaces with a solution of bichromated gelatine and pigment similar

page_text: to that employed in the preparation of the gelatinous tissue as described in my
Patent of February Twenty-ninth, One thousand eight hundred and sixty-four
No. 503, the surface of the glass to be coated with the gelatinous solution
being previously coated with a thin film of caoutchouc or coagulated albumen.
Before using the plates prepared in this way I dry the gelatinous coating, and
in producing the actinic impression upon it I place the uncoated surface of the
glass towards the light transmitted by the negative and camera lens. I
develop the actinic impression produced on the plate as above described, or on
the tissue as described in my Patent of February Twenty-ninth, One thousand
eight hundred and sixty-four, No. 503, by subjecting the gelatinous coating
or film to the action of warm water so as to dissolve the soluble portions;
after developement I surround the plate bearing the gelatine image with a
wall or rim, usually of metal, which being a conductor or rendered a conductor
of electricity on its inner surface, becomes coated thereon with copper; when
the image is electrotyped, and by the deposit of copper uniting with that
formed on the image, rigidity is imparted to the electrotype, and liability to
warp during its formation (which is a difficulty hitherto experienced in taking
electrotypes from gelatine photographs) is thereby removed. Before placing
the gelatine image in the electrotyping vat I act upon it with a solution of a
protosalt of iron, or with a solution of sulphate of alumina, with a view to
surface hardening, and while wet I produce upon it by chemical decomposition
a coating of silver, or I otherwise render its surface electrically conductible;
I then submit it to the electrotype process and obtain a counterpart of the
gelatine image in copper. After the removal of the electrotype from the vat,
and its disengagement from the gelatine image, in order to strengthen it I fill
in upon the back with soft metal other suitable backing to the level of the
top of the rim or wall.
The electrotype plate, produced as above described, I use for what I term
photo-mezzotint printing, which is performed as follows:-Igrease thesurface
of the electrotype by means of a stiff brush, or in any convenient manner; I
then pour ou it a sufficient quantity of slightly warm gelatinous ink, composed
of water, china ink, or other suitable coloring matter, and gelatine in sufficient
proportion to cause the ink to solidify on cooling; over the ink I place a piece
of paper, and then apply an even pressure to the back in such a manner
as to cause the gelatinous iuk to spread over the entire surface of the electro-
type, fill up all its recesses, and displace the excess of ink (over and above
what is required to fill.up the recesses) from between the under surface of the
paper and the upper surface of the electrotype; I maintain the pressure until

page_text: the ink is solidified, and I then remove the paper, which carries with it the
print. I prepare the paper for photo-mezzotint printing by coating its surface
with gelatine, collodion, albumen, or other substance suitable for preventing
coloration of the paper in the high lights of the print. The press which I
employ for giving the impression to the printing paper is fitted with a thin
steel or other metal plate, which forms a kind of elastic tympan, and serves
to impart a gradual pressure (commencing, say, at the middle of the paper)
and extending to the margin so as to spread the ink over the copper-plate
and cause the excess of ink (if any) to exude between the paper and plate at
the ends or margin thereof. This plate may be conveniently fitted to the
under side of a rigid flat plate forming the fixed head of a press, and the
electrotype plate may be raised up to impart the impression to the paper by
means of a screw and hand wheel. The flexure of the plate may be produced
either by a weighted lever acting on a plunger at the back of the steel plate,
or by springs placed between it and the fixed head, which springs are capable
of receding into recesses formed in the under face of the fixed head; or the
elastic plate may have a curved" set," its ends being left free to allow of its
flattening under pressure; or this elastic plate or tympan, either with the
curved set," or curved by pressure from behind, may be fitted to a rigid flat
plate hinged to the bed of a press, and capable of receiving pressure either by
hand or mechanical means. With the view of fixing the prints thus obtained,
that is, of rendering them not liable to injury by water or moisture, I subject
them to the action of a solution of alum, or its equivalent as respects the
property of rendering gelatine more or less insoluble in water; or the same
effect may be obtained by introducing a suitable fixing chemical into the
gelatinous ink.
To produce a photographically engraved plate adapted to ordinary copper-
plate printing, and capable of rendering inversely and in graduated tints the
lights and shades of an ordinary photographic negative, I proceed in the same
manner as has been above described for the production of plates for the photo-
mezzotint style of printing, with the following differences, viz., first, in pro-
ducing the gelatine relief, which constitutes the matrix of the engraved plate, I
add an increased quantity of pigment or coloring matter to the bichromated
gelatine so as to diminish the depth of penetration of the light in the act of
printing the actinic impression upon it. I thus control the height of relief in
the gelatine matrix, and consequently the depth of the engraving of the electro-
type cast taken from the matrix; second, I omit the use of the metallic rin
or wall; and third, I guard against the removal of the printing ink from the

page_text: recesses of the plate in the act of wiping, by forming in the recesses numerous
extremely thin walls, the tops of which are in the same plane as the face of
the plate. The walls may be either in one series of parallel and equidistant
lines, or in two or more series intersecting each other. The single series of
walls gives to the recesses of the plate a trenched structure, while two or more
series gives them a cellular structure; or where the trenched or cellular
structure of the recesses is objectionable, I give them ink-holding capacity by
forming therein numerous spikes or points which terminate in the plane of the
face of the plate. To produce a plate with the trenched cellular or spiked
recesses I form in or upon the negative of the object to be engraved numerous
opaque lines or dots extending over its entire surface, the lines or dots being
equidistant or nearly so, or I produce the said lines or dots in the film of
collodion or albumien upon which the chromo-gelatine tissue or coating is
formed. I obtain the opaque lines by taking in the ordinary way a photo-
graphic negative of a plate of glass coated with an opaque etching ground, and
having the required series of lines drawn upon it with a point, by the aid of a
ruling machine or otherwise, the point cutting through the etching ground to
the surface of the glass. The lines are drawn closer or more open as may be
deemed necessary for the kind of work to be done, and the amount of reduction
to be made in the size of the negative produced from them; I obtain the
opaque dots by taking (in the ordinary way) a photographic negative of a
dark screen, perforated with numerous minute holes, equidistant or nearly so;
or I obtain the dots by means of fine particles of pulverulent opaque matter,
either dusted upon the negative of the object to be engraved, or applied thereto
by means of a solution of gelatine or other suitable vehicle having the
said fine particles of opaque pulverulent matter diffused through it. The
actinic impression having been obtained by the use of the negative pre-
pared as above described on the gelatine coating or film, and developed by
means of warm water, as described above, I treat it with a solution of alum or
a protosalt of iron with a view to indurate the gelatine image; I then render
its surface electrically conductibleas above mentioned, and produce therefrom
a copper-plate by the electrotype process. This plate I use in the ordinary
manner of a copper-plate engraving, except that in printing from it I employ
an ink of such transparency or weak colorific power as to yield prints
possessing gradation of light and shade proportional to the different depths of
the recesses of the engraved plate.
That part of my Invention which relates to typographic and lithographic
printing consists chiefly in the production of what I term a crayon photograph

page_text: (that is to say) a photographic image in which gradation of shade is produced
by dots of opaque matter, more or less aggregated as the shading is darker or
lighter, and therefore corresponding to a crayon drawing in the principle on
which the gradation of shade is produced. In an ordinary photograph
gradation of shade is continuous, and is produced by thicker or thinner strata
of semi-opaque coloring matter. Surface printing is not capable of rendering
this kind of gradation of shading, but it can give the granular or dotted
gradation which characterises the crayon drawing. I therefore convert by
photographic means the continuous gradation, such as an ordinary photograph
possesses, into the granular gradation similar to that of a crayon drawing.
The crayon photograph may be produced in various ways.
The following are the methods which I prefer :-I make a solution of
gelatine, and add to it bichromate of potash or ammonia, or other suitable
compound of chromic acid, and also a certain proportion of charcoal or other
opaque substance in such a state of division or granulation that when diffused
through the gelatine solution, and spread upon glass in a thin layer, the opaque
particles will shew distinct granularity with interstices between particle and
particle.
In using the above-mentioned gelatinous solution, I spread it upon a
level surface of paper, glass, or other suitable substance. (When glass is used
to receive the gelatine it is previously prepared with oxgall, or otherwise, to
facilitate the stripping of the sheet therefrom previously to its being used in
the printing frame.) The coated surface is suitably placed for rapid drying,
and guarded from the action of injurious light. Where the gelatine tissue
is not required for immediate use I prepare it on a basis of paper, and omit
the bichromate in its preparation; and when required for use I render such
tissue sensitive by impregnating it with a solution of the bichromate salt.
When the sensitive gelatinous sheet is dry I place it in a printing frame
beneath an ordinary photographic negative or positive of the object to be
printed. In doing this I put that surface which was uppermost during the
solidification of the gelatinous solution next to the negative or positive plate;
I then expose the printing frame to light in the usual manner, taking care
that the incidence of the light is at right angles with the plane of the photo-
graphic surfaces; after exposure I remove the tissue from the printing frame,
and coat its actinically impressed surface with a solution of caoutchouc and
dammar in benzole; I also coat a plate of glass with the same solution, and,
having allowed the solvent to evaporate, I press the two coated surfaces
together to effect their adhesion.
After mounting the tissue on the glass in

page_text: the manner above described I subject it to the action of warm water, so as
to dissolve away those portions of the gelatine which have not been rendered
insoluble by the action of the light. Instead of producing the actinic im-
pression by the superposition of a negative or positive as above described
I sometimes obtain it by means of the camera, and when operating in
this way I form the chromo-gelatine coating on glass in such a manner
that the particles of opaque matter are fewest and smallest next to the
glass, and increase in size and number towards the exterior surface
of the coating; this I am enabled to do by inverting the glass while the
gelatine is in a fluid state. When the opaque particles are thus distributed
through the gelatine coating, instead of removing it from the glass I expose
the coated plate (when the gelatine is set or dry) in the camera, placing the
uncoated surface of the glass towards the light. The impression obtained is
developed by means of warm water, as in the case of the tissue mounted on
glass after exposure.
The crayon photograph may also be produced by diffusing the iodide,
chloride, or bromide of silver in a granular or pulverulent form through col-
lodion, albumen, gelatine, or other suitable vehicle, the image being obtained
in the usual manner, and either in the camera or in the printing frame.
Another mode of forming the crayon photograph is by dusting the charcoal or
other granular opaque powder upon a photographically impressed surface of
such character that by exposure its hygroscopic properties have been modified
in different parts by light transmitted through a negative or positive photo-
graph. The means of producing such surfaces are well known.
Having obtained the crayon photograph in the manner above described, I
employ it instead of an ordinary negative or positive photograph to produce
with the aid of any of the well-known processes a typographic, lithographic, or
zincographic printing surface.
Having now set forth the nature of my Invention of "Improvements in the
Production of Printing Surfaces by Photographic Agency, and in Obtaining
Prints therefrom," I claim with respect to the photo-mezzotint process,-
First, the improvements above set forth in producing the printing surfaces,
aud in obtaining prints therefrom.
With
And, secondly, the means above described for removing from gelatine
prints the liability to injury from contact with water or moisture.
respect to the copper-plate system of printing, I claim the process above
described for producing the ink-holding printing plates.
And, lastly, with respect to typographic and litho or zincographic printing,

page_text: I claim transmitting the continuous gradation of shade peculiar to the
ordinary photograph into an equivalent of the granular shading peculiar to a
crayon drawing, as above described, for the purpose of obtaining printing
surfaces.
In witness whereof, I, the said Joseph Wilson Swan, have hereunto set
my hand and seal, the Sixth day of January, in the year of our
Lord One thousand eight hundred and sixty-six.
Witness,
FRED. WALKDEN,
66, Chancery Lane.
JOSEPH WILSON SWAN. (L.S.)