Improvements in the Production of Colour Prints.
Year: 1897

page_text: Date of Application, 20th Dec.,.
1897
PROVISIONAL SPECIFICATION.
Improvements in the Production of Colour Prints.
I, HEINRICH JAKOB BURGER, of 33, Pestalozzi Strasse, Zürich, Switzerland,
Lithographer, do hereby declare the nature of this invention to be as follows:-
For the purpose of producing colour prints of a superior quality and in a
quicker and more convenient manner than heretofore I employ a positive film for
producing a printing plate for the warm tints and lights (such as ochre yellow
buff and red) and a negative film for producing a printing plate for the drawing
outlines and for the shadow parts or cold tints. (such as blue and grey) whilst the
middle tints and the finishing tints are made with a suitable ink washed in with
a brush; I prefer an ink made with asphaltum syr, lithographic ink and shellac
dissolved in oil of turpentine and diluted as required. The finishing is done with
a suitable dry rubbing ink by the aid of a stump and an alpaca rag; I prefer a
rubbing ink made with tallow, lithographic chalk spermaceti, beeswax and lamp
black this gives the plate the necessary greasiness.
In this way I obtain warm tints and cold shadows and also all intermediate
tints, the desired printing surfaces are obtained much quicker and easier than
heretofore, and the printing plates made by the use of the films need very little
touching up; also a much finer grain is obtained than by the usual processes
with ordinary lithographic ink or by the use of lithographic chalk lines.
Dated this. 20th day of December 1897.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.
Improvements in the Production of Colour Prints.
1, HEINRICH JAKOB BURGER, of 33, Pestalozzi Strasse, Zürich, Switzerland,
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
the following statement:.
In the heretofore usual photo mechanical printing processes the photographic
picture or print has been produced by using either a positive or a negative film to
obtain copies, under exposure to the sun or electric light upon a plate or other
suitably prepared, surface for instance by pouring on it an asphalt solution or
other substance sensitive to the light. By such a process the parts covered by the
dark portion of the films and thus protected against; the light remain, soluble

page_text: while the parts touched by the light or lying under the light part of the film
become insoluble.
If the plate is then after exposure to the light treated with a solvent, this latter
only dissolves the parts not acted on by the light, for instance the layer of asphalt,
and a deep etching or a high etching is obtained all according to the employment
of a positive or a negative film. The latter process is especially employed when it
is desired to produce pictures like photographic colour prints.
By such transfer from negatives to printing plates be it by an asphalt, albumin,
enamel or any other process it could not heretofore be avoided that the printed
copies become wholly lighter or wholly darker according to the greater or less
distinctness of the negative employed, the longer or shorter exposure the wash-
ing &c. but otherwise similar, that is to say that they all bear the same relation
between the light parts (the deep, washed out places) and the shade parts (the
higher places not affected by the washing medium). And thus it appears that in
a printing plate which is to print the light parts intensely for instance yellow,
these light places are the very ones that take the least colour, and appear pale in
the picture.
This defect has been tried to be remedied by touching up the negative or by
printing the colours on singly on each copy, and by making several negatives or
by reserving the light or warm tints by coating with gum shellac or the like, in
order later on to obtain the necessary colour tints by drawing with lithographic
chalk or lithographic ink..
But such a process is tedious and long as every man in the trade knows.
Now according to my invention and for the purpose of producing colour prints
of a superior quality and in a quicker and more convenient manner than hereto-
fore I employ a positive film for producing a printing plate or surface on stone,
zine or other suitable metal by a known process for the warm tints and lights
(such as ochre, yellow, buff and red) and I similarly employ a negative film for
producing a printing plate or surface for the drawing outlines and for the shadow
parts or cold tints (such as blue and gray). The intermediate tones appear on
both printing plates and may be called warm intermediate tones and cold inter-
mediate tones. The tones existing between light and shade are specially treated
with a suitable ink which may conveniently be washed in on both printing plates
with a brush. I prefer an ink made with asphaltum syr, lithographic ink and
shellac dissolved in oil of turpentine and diluted as required. Suitable propor-
tions are 2 parts of the asphalt, one of lithographic ink and ¼ of shellac to b
dissolved in 10 parts of oil of turpentine.
The finishing up and softening off is done on the printing plates with a suit-
able dry rubbing ink by the aid of a stump and an alpaca rag; I prefer a rubbing
ink made with tallow lithographic chalk, spermaceti beeswax and lamp black.
Suitable proportions are 5 parts of mutton tallow 10 of lithographic chalk 3 of
spermaceti, 3 of beeswax and 1 to 2 of lamp black, first I melt the tallow,
spermaceti and beeswax, then add the lithographic chalk, then skim it, then I
add the lamp black and at last the liquid is poured into moulds. This rubbing
ink gives the plate the necessary greasiness.
The lightest parts in the plate may if required be scraped or rubbed out.
Finally all that does not belong to the color is removed by chloroform or other
suitable solvent.
The printing surfaces arc etched in the usual manner.
By the aforesaid process I obtain printing surfaces corresponding to all shades
of tints from the darkest or coldest to the very lightest. The printing plates made
by the use of the films need very little touching up, and a much finer grain is
obtained than by the usual processes with ordinary lithographic ink or by the use
of lithographic chalk lines.
The two aforesaid printing plates produce a complete photographic picture.
The number of these plates may be multiplied in the usual manner according to
the number of colours to be used.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. Process for producing chromotypes photomechanically consisting in printing
the drawing, the shadows and the cold tints by means of a printing surface pre-
pared from a negative film, and the warm tints by means of a printing surface
prepared from a positive film, the intermediate tones being treated by brushing
in on both printing plates a suitable asphalt ink and by finishing with a suitable
dry rubbing ink, substantially as set forth.
2. The ink consisting of asphaltum syr, lithographic ink and shellac dissolved
in oil of turpentine substantially in the proportions named.
3. The dry rubbing ink consisting of tallow, lithographic chalk, spermaceti wax,
and lamp black substantially in the proportions named.
4. As an improved article of manufacture a colour print made by the use of a
printing surface prepared from a negative film, for the drawing and shadow parts,
and by the use of a printing surface prepared from a positive film for the warm
tints, the intermediate tints being treated by brushing in on both printing surfaces
a suitable asphalt ink and by finishing with a suitable dry rubbing ink.
Dated this Nineteenth day of September 1898.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.