IMPROVEMENTS IN PHOTOGRAPHIC PRINTING
Year: 1879

page_text: LETTERS PATENT to Joseph Wilson Swan, of Newcastle-on-Tyne, in the County
of Newcastle, Chemist, for the Invention of "IMPROVEMENTS IN PHOTOGRAPHIC
PRINTING."
Sealed the 20th January 1880, and dated the 22nd July 1879.
PROVISIONAL SPECIFICATION left by the said Joseph Wilson Swan at the
Office of the Commissioners of Patents on the 22nd July 1879.
JOSEPH WILSON SWAN, of Newcastle on Tyne, in the County of Newcastle,
Chemist. "IMPROVEMENTS IN PHOTOGRAPHIC PRINTING."
My Invention has for its object to increase the rapidity of photographic printing
on paper, a want which has greatly diminished the utility of the methods of
photographic printing in common use.
My Invention consists in the preparation and use of paper coated with bromide
of silver in a state of minute subdivision diffused through gelatine or albumen.
This coating is rendered more or less insoluble in water, the effect being produced
in the case of the gelatine and bromide coating by means of chrome alum, sulphate
of alumina, or other suitable agency, and in the case of the albumen and bromidė
coating by steam or other suitable agency. Paper prepared in this manner is used
either for printing from a negative in the usual manner by superposition, or in a
camera obscura, if an enlarged or diminished photograph is required. In either
case the latent impression produced by the action of light during exposure in the
printing frame or camera is developed by a suitable developing agent, preferably a
mixed solution of ferrous and potassic oxalates; the print thus produced is fixed by
an alkaline hyposulphite, or other suitable solvent of bromide of silver, and is
finally washed with water. In all the various operations of the process of printing
on this highly sensitive paper it is essential that the greatest care be taken not to
expose the paper in its sensitive state to any chemically-active light, except that
which has been transmitted by the negative. In printing by superposition, I prefer
to use gas or other artificial light to produce the impression, and I so vary the
distance of the light from the negative or the light's intensity, that negatives,
dissimilar in the degree of their opacity, may all yield their prints at an equal
time-rate. To facilitate printing at a uniform and rapid rate, the sensitive paper
may be used in long bands, and by means of automatic mechanism may be moved
on step by step periodically through a space equal to the width or length of the
print, the negative being screened from the light during the movement.

page_text: 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 22nd
January-1880.
=
JOSEPH WILSON SWAN, of Newcastle-on-Tyne, in the County of Newcastle,
Chemist. "IMPROVEMENTS IN PHOTOGRAPHIC PRINTING."
My Invention has for its object to increase the rapidity of photographic printing,
a want which has greatly diminished the utility of the methods of photographic
printing in common use.
It consists in the preparation and use of paper or white plates of glass, porcelain,
or enainelled metal coated with bromide of silver in a state of minute sub division
diffused through gelatine or albumen, the coating being rendered more or less
insoluble in water by suitable means. In the case of the gelatine and bromide
coating, I render the coating more or less insoluble in water by means of chrome
alum, or sulphate of alumina and ammonia, or sulphate of alumina and potash (i.e.,
common alum), and in the case of the albumen and bromide coating, I render the
'coating insoluble in water by subjecting it to the action of steam.
I employ the paper or plates prepared with the aforesaid coating, either for
printing from a negative in the usual manner by super position on a negative, or if
an enlarged or diminished photograph is required by means of the camera obscura.
In either case the latent impression produced by the action of light during exposure
in the printing frame or camera is developed by a suitable developing agent,
preferably a mixed solution of ferrous and potassic oxalates, and is fixed by means
of a solution of an alkaline hyposulphite or other suitable solvent of bromide of
silver, followed by washing with water. In the various operations of the process
of producing and printing on the highly sensitive paper or plates herein described,
extending from that point of the process at which the bromide of silver is formed
to that other point at which the bromide of silver is dissolved and removed from
the paper or plates, it is essential that the greatest care be taken not to expose the
paper in its sensitive state to any chemically active light, except that which has
been transmitted by the negative employed in the operation of producing the
photogenic impression.
In printing by super position, I prefer to use gas or other artificial light to
produce the impression, and so to adjust it either by varying the distance of the
light from the negative, or by varying the intensity of the light, that negatives
dissimilar in the degree of their opacity may all yield their prints at an equal
time rate. To facilitate printing at a uniform and rapid rate when paper is em-
ployed, it may be used in long bands, and by means of automatic mechanism may
be moved on step by step periodically through a space equal to the width or length
of the print, the negative being screened from the light during the movement.
The manner in which the material for producing the sensitive coating is prepared
is open to great variation as regards the proportions of the several ingredients and
the mode of their combination. I therefore make no claim for any fixed proportions
of the ingredients, nor for any special mode of combination. In order that the
manner of carrying out my Invention into practice may be completely understood,
I give the following examples touching both these points. First, of a gelatino
bromide coating compound; and second, of an albumeno bromide coating compound.
For producing the gelatino bromide coating compound, I take of gelatine 1000
grains; water, 10,000 grains; nitrate of silver, 600 grains; bromide of potassium
450 grains.
I dissolve the gelatine and bromide of potassium in the of water, and the nitrate
of silver in the remaining 1th of the water, and I add the last named solution to the
first named solution at a temperature of 100° Fahrenheit; make the addition
gradually and with agitation sufficient to produce a complete intermingling of the
two solutions. I then subject the mixture to a temperature of 125° Fahrenheit
during three hours, or more or less according to the degree of sensitiveness required.

page_text: I then allow the compound to solidify by cooling, I break it up into small masses,
and wash it with water frequently renewed during one hour, and I finally re-
'dissolve the gelatino bromide compound by raising the temperature to 110°
Fahrenheit, and I then take 10 grains of alum and 30 grains of carbolic acid, and
500 grains of water; I add the carbolic acid and the alum to the water, and stir
until solution has taken place. I then mix this solution gradually with the gelatino
bromide compound, and after straining through a filter of muslin or other suitable
material, I spread the said compound on sheets or bands of paper, or on plates of
opal, glass, porcelain, or enamelled iron or other metal in such a manner as to
produce a thin and even coating.
For producing the albumino bromide compound, I take of gelatine, 200 grains;
water, 10,000 grains; nitrate of silver, 600 grains; bromide of potassium, 450
grains.
I dissolve the gelatine and bromide of potassium in ths of the water, and the
nitrate of silver in th of the water, and I add the last named solution to the first
named solution at a temperature of 100° Fahrenheit. I make the addition gradually
and with agitation sufficient to produce a complete intermingling of the two
solutions. I then subject the mixture to a temperature of 125° Fahrenheit during
three hours, more or less, according to the degree of sensitiveness required; I then
add a sufficient quantity of strong methylated spirits of wine to cause a precipi-
tation of the combined gelatine and bromide of silver. This precipitate I wash
with water so as to remove the nitrate of potash formed as a bye product, and after
such washing, I add it to the whites of twenty eggs previously whipped and filtered,
and apply sufficient heat to cause it to mingle with the albumen solution. I then
filter the compound through muslin or other suitable material, and spread it upon
sheets of paper or upon plates of opal, glass, porcelain, or enamelled iron or other
metal in such a manner as to produce a thin and even coating. The coating being
dry, I subject the coated paper and plates to the action of a bath of steam so as to
produce insolubility of the coating.
In carrying into effect the above described processes for the preparation of the
gelatino bromide compound, and for the preparation of the albumino bromide com-
pound, and also in the subsequent operations yet to be described, using the same, it
is essential the greatest care be taken not to expose these compounds or paper or
plates coated with them to any chemically active light, except that which has been
transmitted by the negative employed in the operation of producing the photogenic
impression. This precaution refers to all the operations extending from that point
of the process at which bromide of silver is formed to that other point at which
the bromide of silver is dissolved and removed from the coated paper or plates.
I apply the paper or plates coated with either of the above described compounds
to the purpose of positive photographic printing in the manner hereinbefore
described, that is to say, I either produce the photogenic impression upon the
sensitive paper or plate by light acting directly through a negative placed in
immediate contact with the paper or plate, or by means of light transmitted by a
negative and lens to the paper or plate placed in the focus of the lens. After
the requisite exposure to the action of light, and preferably to artificial light,
as above described, I immerse the sensitive and impressed paper in a solution
of ferrous oxalate formed by dissolving ferrous oxalate to saturation in a saturated
solution of potassic oxalate, to which is also added bromide of potassium in the
proportion of eight grains to each imperial pint of the said saturate solution of ferrous
oxalate in potassic oxalate solution. By the action of this solution the effect of
the impression produced by light is developed, and a positive image of the object
depicted by the negative results. After development of the image, I wash the
print in water, I then immerse it for an hour in a 20% solution of hyposulphite
of soda, and again wash in water until the hyposulphite of soda is completely
removed.
In the case of prints produced upon paper, if it be desired to give a glossy
surface to the print, I apply the printed surface while wet to a plate of glass waxed

page_text: in_a_manner_usual in producing glazed photographs, and I allow the print to dry in
this position.
Having stated the nature of my Invention, and the manner in which the same is
carried into effect, I wish it to be understood that I do not claim the particular
mode of producing the sensitive gelatino bromide compound, nor the particular
mode of producing the albumino bromide compound herein described, but I claim
the application of these or any similar mixtures of bromide-of-silver with-gelatine-
or albumen to the forming of an insoluble sensitive coating for paper or plates for
the purpose of producing positive photographic prints thereupon, and I claim the
application of such coated paper or plates to the production of positive photographic
prints in conjunction with the employment of the solution of ferrous oxalate herein
described as the developing agent.
In witness whereof, I, the said Joseph Wilson Swan, have hereunto set my
hand and seal, this Twentieth day of December, in the year of our Lord One
thousand eight hundred and seventy nine.
JOSEPH WILSON SWAN. (L.S.)