IMPROVEMENTS IN POLY- CHROMATIC PRINTING, PARTLY APPLICABLE TO OTHER PURPOSES
Year: 1881

page_text: LETTERS PATENT to John Rudolph Meihé, of No. 2, Laurence Pountney
Hill, in the City of London, for an Invention of "IMPROVEMENTS IN POLY-
CHROMATIC PRINTING, PARTLY APPLICABLE TO OTHER PURPOSES." A com-
munication from abroad by Friedrich Carl Hoesch, of Nürnberg, in the
Kingdom of Bavaria.
PROVISIONAL SPECIFICATION left by the said John Rudolph Meihé at the
Office of the Commissioners of Patents on the 12th August 1881.
JOHN RUDOLPH MEIHÉ, of No. 2, Laurence Pountney Hill, in the City of
London. "IMPROVEMENTS IN POLYCHROMATIC PRINTING, PARTLY APPLICABLE
TO OTHER PURPOSES." [A communication from abroad by Friedrich Carl Hoesch,.
of Nürnberg, in the Kingdom of Bavaria.]
This Invention relates to an improved production of colored pictures, whereby
an enhanced effect is arrived at by fewer impressions than at present, and it is
especially applicable where the agency of light is employed in producing the picture
required. It also relates to an improved method of ascertaining the kind and
proportion of colours required which is applicable and of service where colors are
employed in the arts.
It is well known that the three colours, red, yellow, and blue, form the basis of
all colours, and their admixture in varying proportions produce all the tints with
which we are acquainted. The proportions of certain colours required to produce
other colors are also known, but owing to imperfections in the coloring materials
at our disposal we are unable to produce the fullness or richness of natural
coloring.
In order to overcome the difficulties thus arising, my correspondent has devised
a chromatic scale whereby we may measure or define the color or colors in the
object to be copied, and in the materials at our disposal for reproducing the same.
For example, in colored printing I first take a photographic negative of the object
to be reproduced, and from this negativo obtain several copies by the agency of
light, each copy however arranged so as to receive a certain proportion of light in

page_text: order to be acted upon by a corresponding color, and these impressions are then
transferred or printed from in the usual manner.
The impressions therefore are required to receive a certain color and amount of
that color, which latter is determined by the action of light upon the sensitive
coating on the plate which receives the impression from the original negative;
each impression has then the image of the object in the proportion and gradation
of the color required, and if we now print in the successive stages of the colors
employed, as determined by the aid of the chromatic scale, the forms, colors, and
gradations fall into their natural places with the proper blending and clearness of
effect.
The said chromatic scale may also be used in determining the amount of and the
colors required in producing a given effect where heat or chemical action changes
the colors employed, as in glass, enamel, porcelain, and other printing.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Rudolph Meihé in the Great Seal Patent Office on the
10th February 1882.
JOHN RUDOLPH MEIHÉ, of No. 2, Laurence Pountney Hill, in the City of
London. "IMPROVEMENTS IN POLYCHROMATIC PRINTING, PARTLY APPLICABLE TO
OTHER PURPOSES." A communication from abroad by Friedrich Carl Hoesch, of
Nürnberg, in the Kingdom of Bavaria.
This Invention relates to an improved method for the production of pictures in
colours, whereby an enhanced effect is arrived. at by fewer printings than in the
usual process, and it also provides a means whereby less than ordinary skill may
determine and apply the requisite amount and shade or shades of colour necessary
for a given effect, not only in the case of colour printing, but in many processes
in the arts where colour is employed.
It is generally understood that three primary colours, red, yellow, and blue, or as
some think red, green, and violet, with their admixtures produce all the tints with
which we are acquainted, and the proportions of certain colours, which when
mixed, produce certain others are also known; and we also know that the intensity
or shade of a particular colour is affected by the amount or kind of light falling
upon it, the colour or colours adjoining it, and that certain substances are so
changed by heat that only highly trained skill can foretell the result.
In representing natural or imaginary objects in colour so as to yield a desired
effect, we meet with certain difficulties, and it is the object of this Invention to
overcome some of these, while at the same time reducing the cost of the process.
Some of these difficulties arise from the impurity of the colours used, the varying
effect one colour has upon another, the power of absorption of the material printed
upon the colour, texture, and smoothness of the paper, and the differing character
of the skill employed in defining, proportioning, and arranging the pigments
required in the process.

page_text: The following is the method that it is preferred to follow in making use of this
Invention, although it may be varied in some particulars without materially
affecting the result.
Take several copies, say six or seven, of the picture or object it is desired to
reproduce by photography or other suitable means, all of the same size, and upon
one of these copies denote the colours or shades to be used by figures or other
symbols on those parts where the said colours are to be applied. These shades
and their symbols are determined by means of a chromatic scale to be described
hereafter.
Then take a clear copy, and by the aid of the marked one paint upon it at
all those parts where the symbols indicate a colour, such as red for instance, but
using a wash of grey of different shades, the lightest tint of grey representing the
lightest tint of red in the original, and in the corresponding place, the darkest
shade of grey representing the deepest shade of red in the original, and so on
through the varying shades of red, but all painted in grey upon the copy, the
shades being properly blended into each other in the desired manner; the remainder
of the copy untouched by any of the shades of grey is then painted over with
white pigment, or otherwise effaced.
The other copies are then painted in grey in a similar manner, each copy indi-
cating its own special colour, and this is done not only for the three primary
colours, but may also be done for a neutral or defining tint, and any particular
local colour required to heighten the effect, but in all cases using grey to denote
upon the copy its special colour. Beyond these five colours it will be rarely
necessary to go.
These copies thus prepared are now ready to be photographed to the required
size of the picture wanted, and the negatives thus produced are used to obtain
heliographic or gelatine relief-plates in the usual manner. It will be seen that
each plate is now ready to receive its corresponding colour in all its graduations
and in the proper places only, the gelatine not being acted upon or hardened else-
where through the employment of the white pigment upon the copy.
The relief-platos may now be put upon the press, and each plate inked with its
appointed colour, and copies struck off; and it is obvious that if the colours and
graduations have been determined and placed with accuracy, the printing will
shew them combined with all their desired blending and clearness of effect.
Some pictures may be produced with the wished for effect in three printings,
while others may require the addition of a strong local tint to bring out some
special feature, and also a general neutral or defining tint, but beyond these five
printings, in as many colours, it will be seldom necessary to go, but should it be,
the procedure will be as before.
The chromatic scale is made as follows:-On a flat surface of card, paper, or
other suitable substance, rule, say, 40 to 50 horizontal lines, and about the same
number of vertical ones, all at equal distances apart, thus producing a number of
squares; now paint upon some of these squares a grey wash in varying shade of
intensity, for example, five, the lightest being called one fifth of grey, the deepest
or darkest five fifths; this is done upon the paper or card after an irregular form,
leaving many squares untouched for reasons stated hereafter. A photographic
negative is now taken of this grey scale, from which is obtained a heliographic
or gelatine relief-plate (as in the former case of the picture copy) in the usual way,
which indicates precisely the five tints of grey upon its surface, and if then it is
put upon a press, rolled with blue ink for example, and printed from, the copy will
show five differing intensities of blue corresponding with the five shades in the
grey original.
The relief plate may then be cleaned and rolled, say with yellow, still occupying
the same position in the press; but before printing, the paper previously used is
moved the distance of one square in a determined direction, so that it receives the
colour impression partly upon the clear white surface and partly upon the blue
already printed, the result being varying shades of green in the latter case according

page_text: to the varying shades of blue and yellow; and these being known and numbered,
it follows that a shade denoted as two fifths of yellow, and another as four fifths of
blue, will produce a certain shade of green which has a distinctive number given to
it. The remaining colours are printed in the same manner, each time moving the
paper the distance of a square, thus obtaining a large number of simple and
compound tints according as the impressions fall upon clear or coloured portions of
the paper, which, for reference are then numbered and marked with the degree and
colour producing the same, so that one can by comparison with the picture to be
copied at once determine what number of printings and what shades are required
to obtain a desired tint, care being taken to proceed with the printing of the
pictures in the same order of colours as is followed in the making of the chromatic
scale.
As the grey tints from which the heliographic plates are produced may denote
any determined colour, it is obvious that this Invention can be used with the
greatest certainty for those processes in which colouring materials are fixed and
developed by heat, such as painting on glass or porcelain, enamelling, and the like,
the scale being made and treated in the same way as the work to be done.
Having thus described the nature of the said Invention, and the manner of
performing the same, as communicated to me by my foreign correspondent, I have
to state that I do not restrict myself to the precise details herein given, but what I
believe to be novel and original, and therefore claim as the Invention secured to
me by and in terms of the hereinbefore in part recited Letters Patent is,―
First. The production of a coloured picture of any desired object by means of
grey painted copies, each representing a simple colour, and from which negatives
are taken, substantially as and for the purposes described.
Second. The use or application of a chromatic scale, arranged or constructed
substantially as and for the purposes described.
Third. The application of this process to the production of coloured impressions
on porcelain, enamel, glass, or the like, substantially as described.
In witness whereof, I, the said John Rudolph Meihé, have hereunto set my
hand and seal, this Seventh day of February, in the year of our Lord
One thousand eight hundred and eighty-two.
JOHN RUDOLPH MEIHE (LA)
JOHN RUDOLPH MEIHE (La)