Improvements in the Art of Printing on Two-Color Lithographic Presses.
Year: 1897

page_text: Date of Application, 21st Dec., 1897-Accepted, 5th Feb., 1898
COMPLETE SPECIFICATION.
Improvements in the Art of Printing on Two-Color Lithographic
Presses.
I, STEPHEN WATKINS, of Prince's Chambers, Wolverhampton, in the County
of Stafford, Civil Engineer and Chartered Patent Agent, do hereby declare the
nature of this invention (a communication to me from abroad, from JAMES
MCLOUGHLIN, of 874, Broadway, in the City, County and State of New York,
United States of America, Publisher), and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:-
This invention has relation to printing in colors from surfaces, as those of
lithographic stones for example, where the printing is to be done on two-color
presses.
The difficulty heretofore experienced in printing two colors in succession on a
two-color lithographic press has been, that the wet color applied to the sheet
from the first stone sets off on the second stone from the sheet while it is receiving
the second color, and after a few impressions the second stone begins to take the
second color at this point, which is then printed on the sheet in the form of a
smutch and directly on the spot where the first color has been printed by the first
stone. This difficulty does not occur in printing on single-color presses, as the
color previously printed on the sheet is allowed to dry before the next color is
printed; but in two-color presses the second color is printed before the first becomes
dry.
I have discovered that by first selecting and classifying certain colors and tints
to be used in printing a work in color, then grouping these colors and tints in
couples in a certain order, and then placing the colors or tints of each couple on
the stones of the two-color press in a certain order, such a press may be employed
successfully in producing multi-colored work. For example if the two colors
or tints to be printed on the two-color press be of such a character that they may
be superimposed while wet, the stronger and darker color or tint being printed
from the first stone or plate and the weaker and lighter from the second stone or
plate, and the two tints or colors selected for the printing be of such a character
that the lighter may be printed on or over the darker, without injury to the latter,
then excellent work may be done with a two-color press, and it is the art of thus
selecting the colors or tints, arranging them in pairs or couples, and preparing
the stones or plates with the colors or tints of the pair in the proper order or
sequence, that constitutes the essential features of my invention.
It is also desirable in the selection and arrangement of the colors or tints in the
picture to be printed in colors that the darker of the two colors of the pair shall
cover surfaces of less, or no greater, area than the lighter color of the air, and

page_text: that the spots or figures of the darker color shall be included in the area covered
by the lighter color, and this is generally the arrangement in a colored picture.
In carrying out my invention I classify the colors or tints to be used, in pairs,
for harmony, and on the basis that the lighter of the two colors may be super-
imposed on the darker, while the latter is wet, without injury to the darker color.
Also, in arranging the colors in the picture, I am to include the areas to be covered
by the darker color, within the area or arcas to be covered by the lighter color.
Then, in preparing the stones or plates, the darker color is transferred to the
first stone or plate in the two-color press and the lighter color is transferred to the
second stone in the press.
In the accompanying drawing, which illustrates my invention-
Figure 1 shows the first stone with the darker color transferred thereto; and
Figure 2 shows the second stone, with the lighter color transferred thereto.
Figure 3 shows the sheet with both colors of the design or picture printed
thereon, successively, by the two stones.
To illustrate the operation, suppose for example the pair of colors or tints
selected are dark blue and light blue, the dark blue, a, to be printed from the first
stone, A, in Figure 1, and the light blue, b, to be printed from the second stone, B,
in Figure 2. In the process of printing from these stones, the darker color a, is
first printed on the sheet, C,-seen in Figure 3--and the sheet then passes, while
the darker ink is yet wet, to the second stone B, to receive the lighter color b;
but the great pressure of the sheet C on the second stone will, owing to the
fatty nature of the ink, cause the fat from this ink to overcome the resistance
offered by the water on the second stone and thus prepare this latter stone to take
ink at the points where the dark blue ink has been brought into contact with it.
This effect is not apt to be produced until after a few impressions have been
made, as the water on the second stone will offer some resistance; but after a
time the light blue ink from the roller which supplies ink to the second stone,
will be applied on the spots referred to, and this ink will be printed over or on the
dark blue ink on the sheet. The effect of this will be rather to intensify or increase
the depth of the dark blue color, if it be noticeable at all, and the operator will,
in preparing his tints, make due allowance for this. There will be no difference
of color produced in this case, but only a slight difference of intensity of the
darker color, due to the application of one on the other while wet.
Figure 3 shows the sheet C, which the two colors a and b printed thered from
the stones A and B.
If the lighter color were transferred to the first stone, A, and the darker color
to the second stone, B, the effect would be that the lighter color, under the pressure
in the press, would prepare the second stone to receive the darker ink at the points
where the lighter ink on the sheet was impressed upon it, and these points would
take up the darker ink from the roller; consequently, after a few impressions,
the darker ink would be printed on the sheet over the whole
design, the darker ink being printed over that portion of design printed
in the lighter ink from the first stone and practically obscuring it.
Hence the darker color must be printed from the first stone. As stated above,
the effect of printing with the lighter color over the darker. both colors being in
an undried, or wet condition on the sheet and selected according to my invention,
is to intensify the darker color slightly but not to produce a different color.
Where a different color is to be produced by superimposing colors, it is preferable
to print the second color after the first is dry. For example, such colors as green-
produced by superimposing blue on yellow, or purple-produced by superimposing
blue on red may be produced on a two-color press, but as stated above, it is best
to allow the first color to dry before the second is applied. For this reason the
formation of greens, purples, and the like on a two-color press will usually follow
that of ordinary single-color presswork; that is, the two colors required to produce
the compound color will not be put on the press and printed at the same time.
In choosing colors in pairs that will harmonize and mix or blend properly when

page_text: superimposed or run together, the ordinary pigment colors, Red, Pink, Dark Blue,
Light Blue, Deep Yellow, Pale Yellow, Black and Gray, may be paired as
follows.
Red, 1st.
Pink, 2d.
Dark Blue, 1st.
Light Blue, 2d.
Deep Yellow, 1st.
Pale Yellow, 2d.
Black, 1st.
Gray, 2d.
With inks of these colors arranged in this way, run through a two-color press
four times, an eight-color picture or lithograph may be produced without difficulty
provided the directions given above for the arrangement of the colors is followed.
My method of printing on a two-color press is applicable to what is generally
designated lithographic printing, whether it be done from a stone, an aluminum
plate, or other plate absorbent of water.
It must be understood that while I have referred to the printing of an eight-
color picture and have given examples of eight pairs of colors, I do not limit
myself to any numbers of colors in the picture, nor to any particular pairs of
colors or tints; these will, of course, be subject to conditions. There might be,
in some pictures only two colors required and in other ten or more colors; and
other colors or tints than those named may be arranged in pairs.
Having now particularly described and ascertained the nature of my said in-
vention, and in what manner the same is to be performed, as communicated to
me from abroad, I declare that what I claim is:-
1. The herein described improvement in the art of printing on two-color, litho
graphic presses, which consists in first selecting two colors or tints, one darker
or stronger than the other, which may be superimposed in printing while wet,
without injury to the darker color, and then transferring the darker color to the first
stone or plate of the press and the lighter to the second stone or plate thereof,
substantially as set forth.
2. The herein described improvement in the art of printing on two-color, litho-
graphic presses, which consists in first selecting the colors or tints to be used and
arranging them in pairs for application to the picture to be printed, each pair
consisting of two colors or tints, one darker than the other, which may be super-
imposed in printing without injury to the darker color, and then transferring the
darker colors of the first stones or plates to be used on the two-color press and
the lighter colors to the second stones or plates to be used, substantially as set
forth.
Dotad this 20th day of December 1897