Improvements in the Methods of Producing Two or More Coloured Prints.
Year: 1891

page_text: Date of Application, 17th Apr., 1891
Complete Specification Left, 16th Jan., 1892-Accepted. 16th Apr., 1892
PROVISIONAL SPECIFICATION.
Improvements in the Methods of Producing Two or More Coloured
Prints.
1, 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:-
This invention relates to the methods of making two or more-coloured prints
from colour plates or stones and of photographically producing auto-typic colour
blocks or stones and has for its purpose to attain more perfect results than
heretofore.
When making a double print from an auto-typic block in black colour, either
the double prints differ only by greater intensity of colour from the simple prints
that is to say the lines or grains coincide in the second printing precisely with
those first printed; or the lights of the double prints appear grey and the deep
shades disturbed by the two consecutive printings having undergone a parallel
displacement relatively to each other; or in large quiet surfaces dark stripes are
observable which vary considerably in distance from each other. The latter
irregularity is produced by a slight turning of the two printings relatively to each
other. The lines therefore cross each other at interstices which are the smaller
the greater the said turning has been. At the crossing points the lines lie
upon one
another, at all other points beside one another. Two lines lying upon each other
appear lighter than two lines lying beside each other. The more acute the angle
under which the lines cross each other, the more extended is that part where the
lines lie upon and cover each other that is to say the larger become the light
interstices between the dark stripes. When said angle becomes infinitely acute,
the interstice becomes infinitely large; no stripes are formed and the prints
coincide absolutely. This latter result is however in general very seldom attained
owing to the influence of the temperature on the paper and by other reasons. That
a very slight displacement or turning suffices to produce the said irregularities may
be gathered from the fact that auto-typic blocks generally have 5 to 7 lines to the
millimetre, and that consequently the interstice between the lines amounts to about
one tenth to one fourteenth of a millimetre.
The above applies naturally also, and in a greater measure, to the consecutive
printing with several blocks which correspond to different colours, especially if
they have been produced by photography.
When printing consecutively with several blocks in different colours, the prints
again either happen to fit exactly or a displacement or turning takes place. If the
prints fit precisely, certain rays are absorbed and only those colour rays which
are common to two coinciding colours appear as the result of mixture-i.e. pigment
mixture is produced. If however the prints are parallelly displaced, the rays
proceeding from adjoining points are only mixed in the eye of the observer-
e. optical mixture takes place which has results differing from those of pigment
mixture. If the prints have been turned relatively to each other, we have
pigment mixture at the covering or crossing points and optic mixture at all other
places, whereby stripes of different lightness as well as such of different colours are
produced, which, with printing in different colours, frequently result in most
peculiar patterns. This formation of patterns which renders coloured printing
from line plate blocks impossible is entirely obviated by the application of line
plate systems which are inclined under a certain angle relatively to each other.
As mentioned above, the more acute the angle formed by the crossing of the

page_text: lines, the more extended is that part along which the lines cover one another. It
is evident that this part becomes shorter in proportion to the increase of said angle.
Said part, with a crossing angle of 30 degrees is so much shortened that no more
stripes are formed. As, with auto-type printing, a line plate system consists of
two relatively vertical lines, each system must be turned for 60 degrees for printing
three colours upon each other by means of auto-typic blocks. With two colours,
the above crossing angle may vary between 30 and 60 degrees. Also the other
drawback riz, that the colours are mixed either optically or as pigment is obvinted
by the improved method, the lines being compelled through the large angles to
cross each other at small intervals, whereby optic and pigment mixture is always
produced simultaneously.
Dated this 17th day of April 1891
HUELSER & Co.,
Agents for Applicant.
COMPLETE SPECIFICATION.
Improvements in the Methods of Producing Two or More Coloured
Prints.
"
I, EUGEN ALBERT, Doctor of Philosophy, Member and Technical Manager of
the firm of Dr. 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 and
ascertained in and by the following statement :-
This invention relates to the production of printing surfaces for printing in two
or more colours. It consists in the method of using the series of parallel lines
which constitute the basis of drawn colour plates or colour stones, or of autotype
blocks or autotype stones obtained by photographic means, for the several colours
by placing them at certain angles. Without such a change in the angles disturbing
designs or patterns will occur in the superposition of two or more colour blocks.
This is explained as follows:
Should a block consisting of a number of parallel lines be printed twice in the
same colour a result is obtained which may be divided into three classes:
(a.) The double impression differs very little from the single impression, that i
to say each line may register perfectly on the other, Figure 1.
(.) The double impression appears essentially darker than the single impression,
that is to say the second impression is displaced a fraction of the thickness of the
line parallel to the first and therefore the line appears so much stronger or thicker,
Figure 2 or the second is displaced more than one thickness of the line and two
lines appear, Figure 3, which also gives a darker appearance than a single line,
Figure 1.
-
(c.) The double impressions show the formation of stripes. The distance between
the stripes is not always the same, it varies almost with every point. The stripes
being vertical to the direction of the lines, this formation is not caused by inter-
ference, but by an angle formed by the two lines. The explanation of this is that
the better two lines register one on the other (Figures 1 to 3) the lighter they
If we line printed to fiam an angle one on the other they must
appear.
divide at a given point. At this point the lines are smallest and enlarge gradually
to twice their size until they split in two, Figure 4, the two line are lightest
where they cross, that is to say where they register best. A series of parallel
lines printed one on the other at an angle form lighter or darker bands or stripes,
the lighter ones being the series of parallel lines along the cross points and the
darker ones appearing heaviest where the lines are double, Figure 5. The smaller
the angle the broader become the bands or stripes and inversely the greater the
angle the narrower will be the stripes, Figures 6, which disappear entirely at an
angle of about 30 degrees, Figure 7, naturally also at a greater angle, Figure 8.

page_text: Should the two impressions be effected in different colours the result will not
only vary in depth, but also in colour, which may be explained by the fact that in
those cases where the lines lie over each other a pigment mixture takes place,
whereas if alongside each other an optical mixture. At the angle of 30 degrees
however the optical and pigment mixture are equal in all parts and therefore give
an even tone.
The explanations given for series of parallel lines apply in like manner to
photographic autotype blocks which are prepared by means of a tint formed by two
series of lines placed at a right angle one on the other.
When making a double impression from an autotype block in black colour a
result is obtained which may likewise be divided into three categories.
A. The double impressions differ little from the simple impressions, being only
somewhat more intense, especially in the deep shades.
The two impressions coincide absolutely, line on line, grain on grain. The double
impression appears the more powerful as the colour covers better and becomes
more juicy by the twofold printing.
B. The double impressions appear misty in the deep shades, the light
are grey.
The two prints have undergone a parallel displacement relatively to each
other, the grains and lines lying beside each other; consequently the lights
appear grey and the deep shades full.
C. General appearance as under B, except that the large even surfaces show
dark stripes.
The two impressions have been printed at a slight angle relatively to each other;
the lines consequently cross each other at intervals which are proportionately
smaller as the angle becomes greater. At the crossing points the lines lie upon
each other, at all other points beside each other. It is clear that two lines lying
upon each other appear lighter than two lines lying beside each other. The more
acute the angle at which the lines cross each other, the more extended are the light
intermediate spaces.
If the angle becomes infinitely small the light spaces become
infinitely large; no formation of stripes takes place, the impressions coincide
absolutely.
Such absolute coincidence is impossible with a material like paper, the dimensions
of which are greatly influenced by temperature and moisture by the process of
printing of 1000 copies per hour in the steam press. How small the displacement
or turning need be to produce the above mentioned effects may be judged from the
fact that autotype blocks generally have 5 to 7 lines to the millimetre, the interstice
between the lines therefore being only th to th of a millimetre.
The above remarks about the double impression from the same block applies
naturally, and in a greater measure, al-o to the consecutive printing of several
blocks which correspond to different colours, especially if they have been produced
photographically, either by means of reproduction of positives on which the colours
have been separated by the aid of retouching or stopping out or by direct photography
from the original by means of plates made susceptible for extracting the different
colours.
If several blocks are printed upon each other in different colours the following
takes place:
(1) The impressions happen to fit completely; in this case the colours are so
mixed in the sense of coloured glasses placed behind each other that certain rays
are absorbed and also only the colour rays which are common to both colours appear
as the result of mixture, hence pigment mixture.
(2) If however the prints are displaced the mixing of the colour rays emitted
from point lying beside each other takes place only in our eye. This therefore
is a so-called optic-mixture, the results of which are different from those of pigment
mixture.
(3) With a turning of the impressions pigment mixture takes place at the crossing
points, optical mixture at all other places. Thereby not only stripes of different

page_text: lightness, but also of different colouring are produced, which when printing in
several colours often produce the most peculiar patterns. This formation of patterns
which has hitherto rendered colour printing with line plate blocks impossible vanishes
at once with the application of line plate systems which are inclined under a certain
angle relatively to each other.
Only three autotype blocks can be printed on top of each other, because the
autotype tint is formed by lines at an angle of 90 degrees. When superposing the
second tint it is moved round 60 degrees, A A, B B, CC, (Figure 9) and as
the rectangular cross lines A A', BB, CC, halve these 60 degrees in this
manner each line at an angle of 30 degrees. This operation is repeated similarly
for the superposition of the third tint. The same result can be achieved by moving
the tint 30 degrees, A' A', CC, B' B' (Figure 9). These plates cannot be
perceptibly moved more or less than about 30 degrees and 60 degrees without
getting the above formation of stripes, whereas with two plates only the moving
round may vary between 30 degrees and 60 degrees.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what I
claim is
First. Multicolour printing from printing surfaces drawn by means of series of
parallel lines crossed in such a manner that the direction of the lines for each colour
varies by an angle of about 30 degrees, substantially as set forth.
Second. Multicolour printing from colour blocks, plates, stones, or other printing
surfaces, produced by photography by means of screens or tints turned so that the
direction of the lines forming the tint for each colour varies by an angle of either
about thirty degrees or about sixty degrees, substantially as set forth.
Dated this 16th day of January 1892.
DR. E. ALBERT.