Improvements in the Production of Chromolithographic and other Printing Surfaces.
Year: 1888

page_text: Date of Application, 4th Jan., 1888
Complete Specification Left, 2nd Oct., 1388
Complete Specification Accepted, 2nd Nov., 1888
Improvements in the Production of Chromolithographic and other
Printing Surfaces.
We, HENRI WILD-WIRTH and PAUL FELIX WILD of the firm of Orellfüssli and Co.
of Zürich in the Republic of Switzerland Merchants do hereby declare the nature of
this invention to be as follows:-
In all progress in the art of printing it has not yet been found possible to produce
any required number of chromographic printing plates by photography from a single
negative.
This object is attained by the present invention in the following manner.
The grained or smooth stones or metal plates etc. are covered with a layer of asphalt
or other suitable material which is susceptible to light. The plates are thereupon
successively exposed under a negative to daylight or electric light.
After sufficient exposure has been given the design or drawing is caused to appear
by washing with turpentine or other solvent so that on each plate there is exactly the
same picture. Those parts of each plate which are to print in the respective color are
now prepared by a suitable liquid or ink to receive and print such color, and the
remainder of each plate is cleaned.
1000
HERBERT & Co.,
Agents to Applicants.

page_text: COMPLETE SPECIFICATION.
Improvements in the Production of Chromolithographic and other
Printing Surfaces.
We HENRI WILD-WIRTH and PAUL FELIX WILD of the firm of Orellfüssli & Co.
of Leipzig in the Empire of Germany, Manufacturers 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 rests upon the principle of combining a grained surface of a grained
lithographic stone or metal plate with the product or result of the exposure of
asphaltum to light whereby printing surfaces may be produced. The carrying out of
this process has special advantages for chromolithographic printing in the variety of
colour plates that may be made from one negative.
The process consists in treating the said grained stones or metal plates previously
coated with asphaltum as hereinafter described each in three stages so that by the
judicious adjustment and control of these stages a printing surface may be produced
on cach plate suitable for the light or dark colour or for the ground colour for which
the respective plate is intended.
Thus the grey and light blue are treated differently to the red or yellow and these
again differently from the brown and dark coloured stones. The operator knowing
the colours of the picture, may by this process, produce a dozen or more colour plates
which, when printed, one above the other may produce a perfect chromolithograph
without needing a special outline plate.
The first stage of the process consists in exposing the asphalted stone or plate to
the light under the negative. The exposure should be such that the asphaltum under
the transparent portions of the negative should be rendered insoluble through its whole
thickness. The portions under the semi-transparent parts of the negative will then be
insoluble only to a certain depth and those under the densest parts of the negative will
remain easily soluble.
By varying the amount of exposure according to the colour to be printed by the
plate, the coating on the plates for lighter or transparent colours may be rendered
insoluble over a larger area than those for the body colours. The different plates should
in this process be distinguished according to their colours.
The second stage of the process consists in the washing off (with usual solvent)
of all the soluble parts of the coating and also a portion of the less soluble parts.
The brighter colour stones are washed for less time than the darker ones and the
body colours are washed until coating only remains in the thickest part of the insoluble
asphaltum.
The details in the shadows on the bright colour stones which happen in the dark
portions and for which the coating has been rendered very insoluble should be
brought out and this is done by the third stage of the process which consists in
washing from the plate with strong solvent (turpentine benzole) such parts of the
coating as are not required on each plate, the other portions being brushed over
with gum.

page_text: The dark portions are then washed over more or less until removed or details show
up therein to the desired amount to finish the picture when the washing is discontinued
and the gum is removed.
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.
The preparation of a series of chromolithographic plates or stones by coating
same with asphaltum, exposing to light under one negative as set forth, dissolving
away soluble portions, covering where desired with gum or other protective matter
and dissolving the less soluble parts not required on each plate substantially as
before set forth.
Dated this 2nd day of October 1888.
HERBERT & Co.,
18, Buckingham Street, Strand, London, W.C.,
Agents to Applicants.