US1658184A - Method of making printing plates - Google Patents

Description

Feb. 7, 1928. 1,658,184

A. L. BORNKESSEL METHOD OF MAKING PRINTI NG PLATES Filed July 1926 INVENTOR {a ATTORNEY5 Patented Feb. 7, 1928.

AUGUST L. BOBNKESSEL, OI WESTFIELD, NEW JERSEY.

METHOD MAKING PRINTING PLATES.

Application filed July 31, 1826. Serial Io. 126,888.

This invention relates to improvements in preparin printing plates by the process which is nown generally as photo engraving, and more especially concerns the pro- I vision of an improved process for the production of shading or tinting,particularly in colors. The improved process ma also be employed advantageously in blac and white reproduction. I

In reproducing drawings, paintings, photographs, cartoons and the like in colors 1n quantity in a printing press the procedure briefly is as follows: Four printing plates of the drawing, or other material to e reproduced, known as the copy are made, and it is necessary to run the sheet upon which the reproduction is made through the printing press four times," once with each of these four plates in the press. One of these lates is merely an outline of the cop in lack and White lines, called the key p ate, and the other three plates are adapted to print, each with one of the primary colors, red, ellow and blue. These three plates are t erefore appropriately prepared so as to print one particular color upon such portions only of the sheet as should receive their individual color in order to bring out in the finished reproduction the colors of the copy.

Transparent coloring fluids are used so that the three primary colors are made to unite on certain portions of the picture where it is required to reproduce the intermediate colors of the spectrum, such for example, as brown and green. In printing, it is customary to run the sheet through, the press with the three colored printing plates successively and finish with the key plate which is printed over the whole to unite the colors and bring the picture together.

By the employment of the improved process of the present invention the loss entailed through the accidental spoiling of metal plates during the shading process is eliminated, the use of enamel in place of ink (that is, the so-called enameled top) on the color plates is made possible, and a. plurality of identical color plates may be quickly and easily made, thus eliminating the repetition of the more or less laborious work of shading for each duplicate color plate required for reproduction in large quantities.

In the accompanying drawings which show in a more or less diagrammatic manner the sheet ready to transfer t e ink on the screen I to the transparent sheet, Fig. 5 shows the transparent sheet with the screen removed and the dots on the transparent sheet which have been transferred from the inked screen, and, Fig. 6 shows the transparent sheet with the stopping out material washed off, with just the dots required for a certain color left behind.

According to the improved method of my invention a photographic negative, either on glass or a photographic fihn, is first made of the copy 1. This negative is made to the exact size in which it is desired to reproduce the copy, although the copy itself may be either larger or smaller. From this negative a single print is taken on a sensitized metal plate, and is madeinto a printing plate by the usual photo engraving or etchin process. This plate serves as the key p ate containing the outline of the copy. Each of the other three plates for printin the three primary colors, red, yellow an blue is prepared as follows, in accordance with the invention.

Let us assume that the plate for printing the areas containing blue 15 to be made first.

A proof 2 is taken from the key plate to furnish an outline of the picture or other representation of the copy. In case the reproduction is to be printed in the same size as the copy, it is not necessary to make this proof, but the copy itself may be used. The

proof or copy is placed in a frame, properly constructed to hold the proof fiat and in a convenient position for work.

A transparent sheet of celluloid 3, photographic film, glass or the like is placed in the frame on top of the proof, and the surface of this transparent sheet is now appropriately prepared by the employment of shading film or screen to produce a likeness of the shading or tintin of all areas or portions of the copy w ich contain any shade of 'blue, or in which blue is emplo ed in combination with other primary co ors to produce an intermediate color, such for example as green. In manipulating the shading screens the artist is guided by the lines of the proof which are immediately beneath the transparent sheet. The likeness of the areas to be shaded or tinted in red is subsequently transferred to the surface of a metal printing plate in a manner to be described below.

The shading film or screen which is employedconsists of a transparent sheet usually of celluloid or photographic film having minute depressions in one surface there of in the form of fine dots which may be either round or of other suitable shape and which are adapted to receive ink. A considerable number of different designs of these shading screens is provided for the purpose of producing varied degrees of shading or tinting so as to produce a finer or coarser mesh or. texture of dots on the surface of the transparent sheet. Thus, for example the mesh of the differentscreens may vary from about 16 dots or lines to the inch to about 240 to the inch.

After lacing the transparent sheet in the frame a ove the proof, all parts of the plate upon which no blue appears are painted out by hand with a brush, using a gum such for example as gum arabic. This operation is called blocking out or stopping out, and in carrying 1t out, the artist is ided by the line drawing of the proof ng by referring to the copy for the positions of the various colors. The blocked out plate is shown in Fig. 3. After this has een done, a. screen 4 of appro riate mesh to produce the lightest shade 0 blue on the copy is inked on its dotted side with black ink by means of a roller. The inked screen is then laid with its inked side upon the transparent late in the frame and by pressure on the ack of the screen with a stylus or roller, the dotted design of the screen is transferred to the trans arent plate. The coating of gum prevents t e design of the screen from being transferred to the transparent plate except atthose portions or areas which have not been stopped .out with the gum. The screen is then lifted and this completes the application of the li htest'tint or shade.

f it is desired todeepen the shade ofcertain portioilspf the areas which are to be blue, the portions which have already received the appropriate mesh or texture of dots are now stopped out with a coating of m as before, and a screen of finer mesh 15 applied. More often, however, instead of usin a screen of finer mesh, the same screen 1'. at was used for the first operation is moved slightly from its former position and re-applied to the transparent plate. In order to enable East the appropriate and minute amount 0 movement to be given to the screen, the screen is supported in position above the transparent plate by means of a holder which is provided with micrometric adjusters by which the holder may be moved slightly in one direction or another.

If the deepening of the shade is to be obtained by means of this first screen, the screen is inked again after being moved an appropriate amount, and re-applied to the surface of the transparentplate bypressure. Because of the movement of the screen each dot will overlap the corresponding dot previously applied, to a slight extent, depending upon the degree of movement given to the screen by the adjusters. This will, as shown in Figs. 5 and 6, produce an enlargement of the dots over the areas which have been left 'unstopped, and thus increase the density, tint or shade within these areas.

It may be desired to further increase the density of certain portions of the blue areas and if this is the case, the process of further stopping out, and either moving the screen again or changing screens is repeated until the desired texture and shading is obtained. When the shading of the plate has been finished, it is washed with water and the coating of gum is thereby softened and readily removed taking with it all of the dots of ink which lie on top of any of the various coatings. This leaves on the transparent plate only the dotted shading which has been applied directly to the surface'of the plate by the screens.

The likeness of the surface of the sheet for rinting blue which has been produced on t e surface of the transparent sheet is a positive, photographically speaking, that is, it consists of black dots upon a transparent sheet. A holographic negative is therefore produce by making a contact print from the transparent sheet upon a hotographically sensitized plate or film.

be negative thus produced is then printed upon a photographically sensitized metal rinti-ng plate which is thereafter treated y any appropriate photo engraving process to produce a printing plate in which the I dotted shading which was originally produced on the transparent sheet and then transferred to the negative, is raised up in relief from the rest of the surface of the printing plate.

It will be understood that although the term dotted shading has been used in this description, that by appropriate designs on the shading screens, or by appropriate manipulation of a dotted shaded screen, the dotted shading may be modified into a line shading, or a combination of line and dotted shading.

to the photographic emulsion on the metal plate after printmg from the ne ative. The plate is then placed in a bath 0 cold water which softens the photographic emulsion thereon, except where the exposure to light during the printing ha s hardened the emulsion. The softened emulsion is washed off, leaving only the hardened dots or lines. These may then be dusted with some material to increase the acid-resisting properties of the ink and heated to further improve these pro erties. Then the plate is placed in an aci -etching bath which eats away the metal wherever it is not protected by the hardened film of ink. After the etching has progressed to a suitable depth, the open spaces between the printing surfaces are cut to a greater depth by a routing machine, to prevent the possibility of the paper being pressed against them during the printing, and the preparation of the printing plate is completed by mounting it upon a block of wood or other appropriate material.

This completes the preparation of the blue color plate. The other color plates for printing the primary colors red and yellow, are similarly prepared, the principal difference being in the areas stopped out on the transparent sheets. It may also be found desirable to vary the type of screen employed for the three different colors, as certain textures give the best results with each color. It will be understood that three different transparent sheets are prepared for the color plates, one for each color, and that negatives are made from these transparent sheets, and that from these negatives the individual printing plates for printing the different colors are made by a suitable photo engraving process.

It is not necessary, however, that the different transparent sheets for each color be placed on separate sheets of transparent material, but preferably they are all three made side by side upon a single sheet of transparent material, such for example as photographic film.

Inasmuch as the shading work is done upon the surface of a transparent master sheet, any desired number of negatives which are exact copies of the master sheet may be made, and furthermore, any desired number of printing plates may be made by the usual photo engravin process from a single negative. Thus W ere the quantity of reproduction to be made is so great as to require more than one printing plate for the complete run, it is a comparatively simple matter to make the additional printing plates required. A considerable number of printing plates can be made almost as cheaply and quickly as a single plate because the greater amount of work involved is in the shading of the transparent master sheets.

' plates as well as enamele It will further be understood that in making the metal printing plates from the negatives, enamel may be used in place of ink for protecting the printing surfaces from the action of the acid in the etching bath. Thus by my invention it is possible to obtain the so-called enameled to color printing top key plates. Furthermore, the color plates, as well as the key plate, can be made in any metal desired, such for example as zinc or co per or some appropriate alloy of these an other suitable metals.

The invention has been described above particularly in connection with the preparation of plates for color printing, but it will be understood that the method of the invention may also be employed in reproducing in black and white only. Thus, for example an' outline drawing may be traced upon the transparent master sheet, a negative printed from this sheet, and the photo engraved printing plate made from this negative. This procedure is, however, particularly advantageous where the drawing,

instead of being strictly an outline, contains more or less shading. In this case the drawing is traced upon the transparent master sheet, and then the shading is added to this same sheet by the employment of shading screens as described above in detail in connection with the making of color plates. When the shading has been added, a negative is made and a photo engraved plate from this negative, as before. In this way a shaded copy is reproduced in black and white by the use of a single printing plate.

I claim:

1. The method of preparing color printing plates which comprises laying a transparent sheet over the material to be reproduced so that said material is visible through the sheet, stopping out all of the areas of said transparent sheet except over those portions of the material to be reproduced which are to contain a given color, applying an appropriate shading screen to said transparent sheet, and transferring thereto the design of said screen and then removing the stoppingout material, producing a photographic negative of the transparent master sheet thus produced, and making a photoengraved metal printing plate from said negative.

2. The method of preparing color printing plates which comprises laying a transparent sheet over the material to be reproduced so that said material is visible through the sheet, stopping out all of the areas of said transparent sheet except over those ortions of the material to be reproduced w ich are to contain a given color, applying an appropriate shading screen suitably inked to said transparent sheet and transferring thereto by pressure the design of said screen, washing the transparent sheet to remove the ap ic negative of the transparent master those portions of tie material to be reproeet thus produced, and making a photo 911- duced which are to contain a given color, apgraved metal printin'g plate from said negaplying an appropriate shading screen to sand 6 tive.- transparentisheet, transferring to said trans- 3. The method of preparin master sheets parent sheet the design of said screen, and for use in color prlnting w ich comprises then removing the stopping-out material. laying a transparent sheet over the material In testimony whereof I aflix my signature.

' to be reproduced so that said material is visible through the sheet, stopping out all of the AUGUST L. BORNKESSEL.

stop ing out material, producing a photoareas of said trans arent sheet except over

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