Improvements in Letter-press and Lithographic Processes based upon Photography.
Year: 1891

page_text: Date of Application, 16th Apr., 1891
Complete Specification Left, 15th Jan., 1892-Accepted, 16th Apr., 1892
PROVISIONAL SPECIFICATION.
Improvements in Letter-press and Lithographic Processes based
upon Photography.
I, EUGEN ALBERT, Doctor of Philosophy, Member and Technical Manager of
the firm of "Dr. E. Albert" Artistic and Publishing Institute, of Schwabing near
Munich, in the Empire of Germany, do hereby declare the nature of this invention
to be as follows:-
:-
The object of this invention is to provide a means for obviating the drawbacks
connected with the use of the lined or grained glass plate which, in photo-
lithography or in making half tone blocks for the letter press, is placed before the
sensitive film. The number of lines generally varies between 5 to 8 to the
millimetre and if this number is increased, the printing capacity of the negative or
block is prejudiced, while, if it is lessened, the tones lose in richness. Supposing
the proportion of the light line of the line plate to the dark line be 1: 1, the
solarization with a certain size of line plate, is insufficient for a satisfactory repro-
duction and, after etching, the lights prove too dark and without effect, while the
deep tones are adjoined with a middle gray colour.
By altering, in the line plate, the proportion of the dark line to the white in
favour of the latter or vice versa, either the dark or the light shades would be
prejudiced. It is therefore impossible to produce from a coarse line plate, adapted
for the printing of placards or the like, effective and clear blocks.
The said inconveniences are intended to be obviated by the gradual line plate or
scale net, which may be produced in different ways, but preferably and most
securely by bringing the object, when photographing the original line plate, into
connection with a spindle, the revolutions of which are ascertainable by a counting
mechanism. The principle started from in this manipulation is parallel displace-
ment of the net lines. The very small degree of such displacements necessitates
precisely executed mechanism which for instance would render a movement of one
hundredth of a millimetre determinable.
A gradual line plate may be, for instance, produced and applied as follows:
The original line plate, in which the light and dark lines are supposed to be in
the proportion of 1:1, is focused in the usual manner, and the objective adjusted
in the above mentioned machinery. After the sensitive plate has been put in place,
the exposure is commenced, which, to obtain the necessary film for the net negative,
After the lapse of
may be supposed in this instance to last altogether six minutes.
three minutes, the exposure is interrupted and the objective displaced by means of
the arbor to such an extent as would amount to half the thickness of the net lines.
Subsequently the exposure is continued for another three minutes and then the
plate developed and fixed. Each single line of the negative thus produced has two
tones, riz., a grey tone and a black body in the middle thereof.
As after three
minutes' exposure the objective was displaced only by half the thickness of a line
on the negative, the second half of the six minutes' exposure was for one half of
the line a continuation of the first exposure, which accounts for the black body in
the middle of the line of the negative.
If the white line on the original line plate was equal in width to the black line,
the displacement has now caused the grey line with black core to become broader
on the reproduced line plate at the expense of the white line, the proportion being
now 3: 1.
When reproducing an original by means of such a gradual line plate, the grey
line forms an obstacle for all rays of minimal lucidity from the deep shades of the
original and represents in fact an equivalent of the black line. The result is a

page_text: broad dark line and a narrow light line in the proportion: 3: 1, which is favorable
for the reproduction of the shades of an original.
The rays conting from the half tones of the original begin, corresponding to
their intensity, to solarize about the grey line, while the rays from the lights are
sufficiently intense to penetrate the grey line and find an obstacle only in the double
film of the dark middle, that is to say, only the dark core avails for the lights;
the grey line acts as if it were white and the result is the most favorable pro-
portion for the lights, viz. a narrow dark line and a broad light line in the
proportion 1: 3.
The number of scales or gradations may of course be increased according to the
subtleness of the mechanism and size of the net.
The new principle may be applied to simple as well as crossed line plates and
involves for the line plate sizes hitherto used a far greater perfection of the result
attained by mere mechanical means.
Dated this 16th day of April 1891.
HUELSER & Co.,
Agents for Applicant.
| ITVIT LOAN LION,
Improvements in Letter-press and Lithographic Processes based
upon Photography.
I, EUGEN ALBERT, Doctor of Philosophy, Member and Technical Manager of
the firm of Dr. E. Albert" Artistic and Publishing Institute, of Schwabing near
Munich, in the Empire of Germany, do hereby declare the nature of this invention
and in what manner the same is to be performed, to be particularly described aud
ascertained in and by the following statement :-
This invention relates to improvements in letter-press and lithographic processes
based upan photography.
Photo-lithography and half-tone blocks for the letter press are produced as follows:
When taking a photograph of an object, a glass plate supplied with the requisite
lines or grains is placed before the sensitive film and then the negative is exposed
through this net or tint. Owing to the solarisation, or extension of the action of
the light sideways, being proportional to the values of lights and shades, the half
tones of the original are divided into bigger or smaller lines and points. From
such a negative composed of lines and points, the transfer on stone or metal is made
and subsequently the etching takes place in the known manner.
The result of this etching, as far as it is mechanical and without any art-manipu-
lation, is only based upon the usual big or small lines and points of the given
negative according to the lights and shades of the original.
The size of the points, without regard to the character of the original to be
reproduced depends on the number of lines to the millimetro and on the proportion
of the white and transparent lines to the black and covered ones on the line plate
or tint.
The number of lines to a millimetre ranges from 5 to 8; with a larger number
the printing capacity of the blocks is prejudiced and with a smaller number the
richness of tone is diminished. This drawback arises as follows:
Supposing the proportion of the white to the black line be 1: 1; the solarisation,
with a certain size of the net or tint would no more suffice to contract enough in
the lights the transparent points on the negative, while the covered point attains
in the shades considerable dimensions owing to the wide meshes of the liue plate or
tint. Consequently the lights, after etching, are too dark and without any effect,
while in the deep tones a middle grey is observable immediately beside the com-
pletely dark. If in the net or tint the proportion of the black to the white line
were altered in favor of the latter, the lights would of course profit thereby, but

page_text: but no lights.
It is therefore impossible to produce by a coarse line plate blocks of good effect
and rich in tone, which would be adapted for printing on common placard or poster
paper and for illustrations of daily newspapers etc.
inherent to the photographic line-plate or tint process, that good results reganling
It is still a great drawback
the soft and plastic shades, the tender half-tones and the great clear lights can only
be attained, if the originals are well qualified for this purpose.
De greatly damaged. A larger black line would give better shades
In order to always ensure the said advantages even with unfavorable originals
and with any net or tint it is necessary to employ for the different tones of an
original also different line plates or tints in such a manner that for the shades the
black lines are larger than those for the lights, and for the lights the white lines
are larger than those for the shades.
Such an ideal, impossible as it seems, can be attained by the gradual line plate or
scale net or gradation tint forming the subject of this invention.
plate or gradation tint can be produced in different ways, but the most simple and
A gradual line
accurate manner is the following:
To prepare the negative for the reproduction of an original net or tint the lens
is put in communication with a screw the revolutions of which can be controlled
by a counter. The principle of this manipulation is founded on the parallel
displacement of the lines. The very small degree of such displacements necessitates
accurately executed mechanism, which, for instance would render a movement of
one hundredth of a millimetre determinable.
A gradual line plate or gradation tint may be for instance produced and applied
as follows:
The original line plate or tint, in which the light and dark lines are supposed to
be in the proportion of 1:1 is focused in the usual manner and the objective
adjusted in the above mentioned machinery. After the sensitive plate has been
put in place, the exposure is commenced, which, to obtain the necessary effect for
the net or tint negativo may be supposed in this instance to last altogether six
minutes. After the lapse of three minutes, the exposure is interrupted and the
objective displaced by means of the screw to such an extent as would amount to
half the thickness of the lines. Subsequently the exposure is continued for
another three minutes and then the plate developed and fixed.
of the negative thus produced has two tones viz. a grey tone and a black body in
Each single line
the middle thereof. As after three minutes' exposure the objective was displaced
only by half the thickness of a line on the negative, the second half of the six
minutes' exposure was for one half of the line a continuation of the first exposure,
which accounts for the black body in the middle of the line of the negative.
If the white line on the original line plate or tint was equal in width to the black
line, the displacement has now caused the grey line with black core to become
broader on the reproduced line plate or tint at the expense of the white line, the
proportion being now 3: i.
When reproducing an original by means of such a gradual line plate or scale net
or gradation tint the grey line forms an obstacle for all rays of least intensity from
the deep shades of the original and represents in fact an equivalent of the black
line. The result is a broad dark line and a narrow light line in the proportion: 3: 1,
which is favorable for the reproduction of the shades of au original.
The rays emitted from the half tones of the original begin, corresponding to
their intensity, to solarize about the grey line, while the rays from the lights are
sufficiently intense to penetrate the grey line and find an obstacle only in the double
film of the dark middle, that is to say, only the dark core avails for the lights;
the grey line acts as if it were white, and the result is the most favorable
proportion for the lights, ciz. a narrow dark line and a broad light line in the
proportion: 1: 3.
The number of scales or gradations may of course be increased according to the
subtleness of the mechanism or size of the net or tint. The desired gradations

page_text: can also be produced photographically by other means such as for instance
according to the above mentioned principle of the parallel displacement of the
tint-lines. It is also possible to produce an original gradation tint by any suitable
direct mechanical means. The desired result may also be achieved by displacement
of an ordinary tint consisting of dark and white lines put immediately before the
sensitive plate during the exposure of an original or by the displacement of the
sensitive plate itself. The effect of such a displacement varies for the different
tones of the original because the high lights of the original produce a corre-
spondingly intense netion on the sensitive plate in a fraction of the time of exposure,
the transparent points on the negative diminishing in accordance with the amount
of the displacement. On the other hand the dark parts of the original cannot
produce a chemical action in a fraction of the exposure but only during the whole
time of exposure and therefore the covered points are accordingly diminished.
The new principle may be applied to simple as well as crossed line plates or line
waves and it comprises for the usual size of nets or tints, an important perfection
of the result by mere mechanical means, while, owing to the possibility of
employing coarse line plates or tints, it opens to the photographic processes for
typo- and lithographic prints the new domains of placard or poster printing,
illustrating daily newspapers etc.
Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed, I declare that what I
claim is:
First. A tint, single or crossed, for photographic reproductions with any number
of gradations of tone in its dark linos or line waves, which gradations may be
produced mechanically when making an original gradation tint, or which may be
made by photography, from a tint consisting only of dark and white lines,
substantially as hereinbefore described.
Second. The displacing of the screen or tint, single or crossed, put directly before
the sensitive plate during the photographic exposure of a picture, or the displacing
of the sensitive plate itself, substantially as hereinbefore described.
Dated this 14th day of January 1892.
DR. E. ALBERT.