IMPROVEMENTS IN PHOTO-MECHANICAL PRINTING AND IN APPARATUS TO BE USED IN SUCH PRINTING
Year: 1873

page_text: LETTERS PATENT to William do Wiveleslie Abney, of St. Margaret's
Street, Rochester, in the County of Kent, for the Invention of
"IMPROVEMENTS IN PHOTO-MECHANICAL PRINTING AND IN APPARATUS TO BE
USED IN SUCH PRINTING."
Sealed the 13th May 1873, and dated the 19th February 1873.
PROVISIONAL SPECIFICATION left by the said William de Wive-
leslie Abney at the Office of the Commissioners of Patents,
with his Petition, on the 19th February 1873.
I, WILLIAM DE WIVELESLIE ABNEY, of St. Margaret's Street,
Rochester, in the County of Kent, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN PHOTO-MECHANICAL PRINTING AND IN
APPARATUS TO BE USED IN SUCH PRINTING," to be as follows:-
This Invention consists in improvements in that form of photo-
mechanical printing in which a film of gelatine or other gelatinous
substance is made sensitive to light by the addition of bichromate of
potash, and after having been dried and exposed to light under a photo-
graphic "negative" is inked with greasy inks for the purpose of printing
from it, or making it what is known as a transfer, the greasy inks

page_text: adhering to those parts of the gelatinous film which have been affected
by the light, and are consequently repellent of water, and being rejected
by those parts which have not been affected by light and are conse-
quently absorbent of water. It relates especially to improved methods
of transferring such gelatinous films, and the pictures formed upon them
by the action of light, to the surface of stone, zinc, or other suitable
material, from which pictures are obtained in an ordinary printing press
in the method well understood and practised.
In order to carry out my Invention I take a sheet of paper, linen,
india-rubber, or other flexible material, the surface of which I coat with
a solution of gelatine or gelatinous substance, to which chrome alum,
tannin, or other substance which will render gelatine insoluble may be
added, as herein-after to be described, which is rendered sensitive to the
action of light by the addition of a sufficient proportion of bichromate of
potash in the manner well understood and practised.
The gelatine solution may be applied to the surface of the flexible
sheet described either by floating the sheet upon the solution or by
pouring or brushing the solution upon the sheet. The other solutions
used for the purpose of rendering the gelatine insoluble, or of rendering
it sensitive to the action of light as above described, may be similarly
applied after the gelatine is dried, or they may be added at once to the
gelatine solution, and one floating will then be sufficient. The coated
sheet is then dried in a dark place, or in a place only lighted by red or
non-actinic light, and is then exposed to the action of light under a
photographic negative. After having been sufficiently exposed to light,
the coated sheet is again taken into a place, dark, or only lighted by
non-actinic light, and is soaked in water until the unaltered bichromate
of potash has been washed out (that part which has been acted on by
light being insoluble). The coated sheet is then placed with its printed
side uppermost upon a flat support of glass, metal, or other suitable
material, which I prefer to cover first with a thin film of india-rubber,
gelatine, or gelatinous substance, to which the film is made to adhere
temporarily by expelling the air from between them by the use of an
instrument consisting of a straight flexible tongue attached to a support
and well known as a squeegee," and the film and support are then
pressed together in a suitable press. The surface of the film is then
inked with greasy ink (such as lithographic transfer ink), preferably by
means of a soft roller, until all the parts which are repellent of water (as

page_text: above described) become covered with the ink. The film may then be
placed in warm water for the purpose of dissolving the part of the sensi-
tized gelatine which has been unaffected by the action of light, and
consequently remains soluble (unless made previously insoluble, as above
described), and it is then dried; or the film may be at once dried,
without first washing away such soluble gelatine, in which case I prefer
that the film should be treated with a solution of alum or other substance
which is capable of rendering gelatine insoluble. The picture upon the
film may then be transferred to the surface of stone, zinc, or other suit-
able metal by the methods ordinarily used and practised by lithographic
printers for transferring pictures to such surfaces, and the stone or metal
carrying the picture being placed in a lithographic printing press
pictures may be obtained from it in the usual way.
By my improved method described the gelatinized film is inked whilst
still wet instead of being dry before such inking. The photographic
negative need not be reversed, and it is not important that it should be
very dense in the parts that, if an ordinary silver print is to be printed by
the action of light, should print white.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William de Wiveleslic Abney in the Great
Seal Patent Office on the 18th August 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
DE WIVELESLIE ABNEY, of St. Margaret's Street, Rochester, in the
County of Kent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Nineteenth day of February, in the year of our
Lord One thousand eight hundred and seventy-three, in the thirty-sixth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said William de Wiveleslie Abney, Her special
licence that I, the said William de Wiveleslie Abney, executors,
administrators, and assigns, or such others as I, the said William
de Wiveleslie Abney, 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
-

page_text: lawfully might make, use, exercise, and vend, within the United King-
dom of Great Britain and Ireland, the Channel Islands, and Isle of
Man, an Invention for "IMPROVEMENTS IN PHOTO-MECHANICAL PRINTING AND
IN APPARATUS TO BE USED IN SUCH PRINTING," upon the condition (amongst
others) that I, the said William de Wiveleslie Abney, 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 William de Wiveleslic Abney,
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 consists of an application of the well known fact that
a solution of gelatine or other gelatinous substance when mixed with a
suitable proportion of an alkaline bi-chromate and dried is rendered
insoluble in water by exposure to light. Also further on the fact that
gelatine treated in this manner will take a greasy ink even after being
soaked in or brought in contact with water in proportion to the degree
in which it has been rendered insoluble in or repellent of water by
exposure to light.
In order to carry out my Invention I take a sheet of paper of any
suitable size and I float it for from one to three minutes on a warm
solution of gelatine and bichromate of potash in water, the gelatine
being swelled and dissolved by the aid of heat in the usual way. The
proportions of these ingredients vary according to temperature and the
subject that is to be copied, but the formula which I prefer to use is as
follows:-

page_text: I sometimes treat the paper as before described with a solution of
gelatine without the addition of bichromate of potash, making a stock
of gelatinized paper which will keep indefinitely, and when required for
use I float this prepared paper on a solution of bichromate of potash of
about 35 grains of the salt to the ounce of water and dry. Sometimes
I give the paper a preliminary washing of gelatine, to which has been
added a sufficient quantity of alum or other substance which will render
gelatine insoluble, or I coat it as first described, and I then render it
insoluble by the action of light, and then coat it again as before described.
The object of this is to get a fine surface on which the final sensitive
gelatine film shall rest.
The methods described are well known and practised in photo-litho-
graphy.
I next take a negative of a truc subject in the ordinary manner and
place it in the method well understood and practised in contact with the
prepared paper, which is then exposed to the action of light. Where
the light acts through the transparent parts of the negative there the
gelatine as before stated becomes insoluble, and it also becomes dis-
coloured to a brown tint. When I judge the picture to be sufficiently
printed I take the paper upon which a picture has thus been printed,
and I place it in a dish of cold water or else in cold water, to which a
sufficient proportion of alum or any salt which renders gelatine insoluble
has been added. I then wash out a good deal of the bichromate of
potash which has remained unaltered, a portion of which however I
prefer to leave in the gelatine. When the paper on which the picture
has been printed is thoroughly soaked I take it and place it on a flat
support of zinc, pewter, glass, or other suitable material, and I get rid
of all superfluous moisture either by placing it in a press, drying it with
blotting paper, or leaving the moisture partially to evaporate by any
other convenient means. I then take a soft roller such as that used in
producing the pictures known as heliotypes, and described in the Specifi-
cations of the Letters Patent granted to Ernest Edwards, dated December
8th 1869, and numbered 3543, and dated September 15th 1870, and
numbered 2485, and dated October 20th 1871, and numbered 2799, and
dated January 9th 1872, and numbered 73, and having coated the roller
with transfer ink of the kind ordinarily used by lithographers or with
other suitable greasy ink I roll it over the surface of the picture. Upon
the parts of the picture where the light has acted, and which are consc-

page_text: quently repellent of water, the ink will adhere, whilst upon those
portions which have been unacted upon or only faintly acted upon by
light the ink will not adhere. If the negative be thin (as understood
by photographers) and thus cause what should be unaltered gelatine to
become slightly altered by the light a stiff or thick ink on the roller will
prevent these portions being covered by the ink, as it will only perma-
nently adhere to those parts strongly acted upon by the light, as
explained in the Specification of the Letters Patent of Ernest Edwards,
dated December 8th 1869, and numbered 3543, already referred to.
When it is judged that sufficient ink has adhered to the picture I remove
it, and if thought advisable I place it for a short time in alum and
I
water. This is not necessary, but may be advisable in certain cases.
then dry the inked up picture thus produced, and if the bichromate of
potash has not all been washed out in the previous washing described I
prefer that actinic light should be allowed to fall on the surface of the
print to harden it, and thus prevent the film adhering to the stone or
metal plate, to which after re-damping it is to be transferred for the
purpose of printing from in the printing press. Instead of paper as a
support for the gelatine film I sometimes use fine woven calico, linen,
india-rubber sheeting, silk, or other suitable analogous material. There
is now a complete picture in greasy ink ready to be transferred in the
ordinary manner to stone or metal plates for the purpose of printing
from.
I claim as a novelty the method of "inking in" such a transfer on
gelatine or other colloid body for the purpose of being transferred to
stone or metal plates, substantially as described as being different in all
essentials to any process yet published.
If a "half tone" negative be employed the paper may be used for
obtaining pictures in ink as by the heliotype process already referred to
or by any other of the methods well understood and practised. In such
a case I prefer to coat the back as well as the front of the paper with
gelatine to cause it to adhere to the support. The front of the paper
which is to be in contact with the negative should have a thicker coat
than if the picture is to be used for a transfer as above described.
Another modification of my Invention which I sometimes employ is
as follows:-I coat a sheet of paper or other suitable material with a
solution of gelatine in the manner herein-before described, but I omit

page_text: from such solution of gelatine the bichromate salt, and I only add a
small proportion of alum or other substance which has a tendency to
harden the gelatine or render it insoluble. Upon the sheet thus prepared
I write or form designs by means of any kind of pen or other suitable
instrument with an ink composed of a gelatinous solution or solution of
gum, to which has been added a proportion of a suitable bichromate
sufficient to render such ink sensitive to light when dry in the manner
herein-before described. I sometimes also add to the ink thus prepared
a quantity (in any convenient proportion) of aniline dye, preferably of a
mauve colour. When the writing or designs thus formed have become
dry and have been rendered non-absorbent of water by the action of
light I damp the sheet and then ink it up by means of a roller in the
manner already described, and the writing or designs can then be trans-
ferred to stone or to a metal plate for the purpose of printing from in a
printing press.
In witness whereof, I, the said William de Wiveleslic Abney have
hereunto set my hand and seal, this Twelfth day of August,
in the year of our Lord One thousand eight hundred and seventy-
three.
WILLIAM DE WIVELESLIE ABNEY. (L.s.)