Improvements in or relating to Photo-mechanical Colour Printing.
Year: 1891

page_text: Date of Application, 31st Jan., 1891-Accepted, 7th Mar., 1891
COMPLETE SPECIFICATION.
Improvements in or relating to Photo-mechanical Colour Printing.
We, FREDERICK JENOUR UPTON, of 7, St. Charles Square, North Kensington,
in the County of London, Gentleman, and GEORGE STEPHENS, of 47, Pembroke
Road, Walthamstow, in the County of Essex, Lithographer, do hereby declare the
nature of this invention, and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
This invention relates to improvements in or appertaining to photo-mechanical
colour printing, and has for its objects to wholly or partially dispense with the
highly skilled labour of the lithographic artist employed in preparing for the
printing of the various coloured impressions required to make up a finished coloured
picture, to reduce the time and cost in performing the same, and to produce a more
faithful representation of the original than is possible when depending upon the skill
of the artist aforesaid. The invention is applicable to copying coloured impressions
designs, or pictures-either of the same size as the original, or enlarged or reduced
therefrom for decorative, artistic, advertising or other purposes. The invention is
further applicable to producing naturally coloured representations of persons, or
other natural objects.
In practising the invention, a photographic negative is taken of the object, and
developed, in the usual manner. From this negative (which is made the required
size), several positives are taken upon paper in the photographic printing frame, in
the known way, but the paper itself is specially prepared in a manner described
hereinafter. One positive is taken for each of the following colours; yellow, blue,
red, black, brown and grey and the proper admixture or blending of these colours
will produce any other colour or shade required, in the finished picture, as is well
known.
These positives are subsequently used as transfers, a positive being placed upon
the lithographic stone or other suitable printing surface, to convey to the stone all
the forms or representations upon the original that contained yellow, (for example),
in its composition. Similar transfers are made from the other positives to other
stones, for the blue, red, and other colours named, in the manner well known to
lithographers; and the resultant impressions upon paper of these various stones,
each having its requisite form, position, and inked with its proper colour, (as
represented in the original), makes up the finished picture, in the known manner.
The positives, however, are of a peculiar nature, and each kind of positive used,
as it is printed in the photographic printing frame, is capable only of taking from
the negative so much of the picture as contained the colour for which it was
specially prepared with an exception to be described hereafter. For example,
the positive prepared for a yellow, will take from the negative all the forms thereon
in which yellow was used, but not the parts in which yellow was not used. Similarly,
the positive prepared for the red colour, will only receive a print of the parts in
which red was used, and no other, and so with the blue. But in printing positives
for the black, brown, and grey shades, the positives are exposed to the action
of light for times varying with the shade required. The positive for black is
exposed for the shortest time of the three, the brown positive has a longer exposure
to bring out shades which do not appear on the positive for black while the grey
positive is exposed the longest in order that the most delicate shadows upon the
negative (which contained grey in the original) will be reproduced thereon. It will
be understood that the coloured printing inks employed upon the stones, wil
conform to the shades required by the respective positives.

page_text: The positives for the black, brown, and grey shades should be printed quickly,
the black positive having the least exposure; as already mentioned.
To bring out any slight tints of colour, having no body, the paper should be
coated lightly with a solution of the following ingredients:-
Gelatine
Bichromate of potash
Alcohol
Water
5 parts.
5
22
2
22
88
22
In printing positives for these slight tints, the prepared paper should be exposed
for a considerable time. It is to be noticed, however, that if over exposure takes
place upon the yellow, red or blue positives, slight tints or scum will be
observed thereon, which would affect the quality of the work. This difficulty is
easily avoided, however, but if transferred to the stone these places may be readily
removed in the known manner.
After exposing paper (prepared as previously described) under the negative in
the printing frame, the several positives are coated over with a composition of
ordinary re-transfer ink, with the addition of seven parts of palm oil, and is then
soaked in cold water to remove the surplus ink, which may be done with a sponge
or piece of cotton wool. If the tinted surfaces do not appear at an early stage,
the application of a little spirits of wine and water will produce the desired
result. Subsequently, the positives are well washed in clean water, partially
dried, and then transferred to the lithographic stone or other suitable printing

page_text: surface to produce finished pictures, as already described, in the well known
manner.
It has been found that the pigments employed upon a coloured original have
some effect upon the printed positives, and it would appear, therefore, that the
negative has an increased, though unexplained importance. Without entering
upon debatable ground it is sufficient to say that if the pigments are opaque in
one case, and more or less transparent in another-both being of the same
fundamental colour, as yellow, blue or red-then the result differs to a slight
extent and it is found that in the latter case a longer exposure of the positives is
required in the photographic printing frame.
It will be understood that the quantities or proportions of the several solutions
and preparations named may be varied to some extent, without departing from the
nature or object of the invention. Likewise, other ingredients, than those named,
may be used so long as they produce the desired results, but in practice it has
been found that the various substances, quantities, and proportions above
mentioned, give good results, and are therefore to be recommended. It is also to
be observed that for some kinds of work a smaller number of tints, than that
indicated above, may be sufficient for the object in view, and consequently a fewer
number of positives will be required than has been enumerated.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is:-
1. The herein described improvements in or relating to photo-mechanical colour
printing, comprising the printing of positives upon paper prepared as herein stated
from a suitable negative to produce transfers, the application of each transfer to a
printing surface, and the printing therefrom of impressions in coloured ink of a
desired tint to correspond with each of the said positives substantially as and for
the purpose described.
2. A photographic positive printed from a photographic negative upon paper
prepared as herein stated, and adapted to be used as a transfer to a printing
surface for a special tint or colour, substantially as and for the purpose described.
3. A photographic positive printed from a suitable photographic negative upon
paper prepared as herein stated, to make it sensitive to the yellow shades in the
original, substantially as and for the purpose described.
4. A photographic positive printed from a suitable photographic negative upon
paper prepared as herein stated to make it sensitive to the red shades in the
original, substantially as and for the purpose described.
5. A. photographic positive printed from a suitable photographic negative upon
paper prepared as herein stated to make it sensitive to the blue shades in the
original, substantially as and for the purpose herein described.
6. A photographic positive printed from a suitable photographic negative upon
paper prepared as herein stated to make it sensitive to a special shade or colour as
represented in the original, and subsequently treated with ink for use as a transfer,
substantially in the manner and for the purpose described.
7. The several solutions for preparing photographic positives substantially as
and for the purpose herein described.
Dated this 26th day of January 1891.
FAIRFAX & WETTER,
433, Strand, London, Agents for the Applicants.