US1959992A - Silk screen printing method - Google Patents

Description

Patented May 22, 1934 UNITED STATES PATENT OFFICE 1,959,992 SILK SCREEN PRINTING METHOD Franz Weiss, Chicago, Ill.

No Drawing. Application September 8, 1933, Serial No. 688,697

5 Claims.

My invention relates to-a silk screen printing method and more particularly to the mechanical production of shaded or half-tone silk screens (plates) An object of the invention is to prepare shaded or half-tone silk screens, without the use of photography, and by employing engraved or etched plates;

transparent papers which as negatives for preparing screens. Another, object is to provide a method for the easy and quick making of drawings or designs with shaded advertising cuts and. the like.

and advantages will proceeds.

Heretofore it has efiects on thin papers for Other objects appear as the specification been the practice to make half-tone silk screens photographioally, i. e., by

sensitizing the silk line half-tone photo-plates, furnished by a photo-engraver, or to screen and. exposing it to a shaded drawing on trans parent material made by the Ben Day process. The making of photographical half-tone silk screens is not only a ess requiring the use tedious and expensive procof fine silks, which are expensive and are often ruined by removing the sensitized solution with lye, but also, it requires a separate screen for each color to be printed. Furthermore, there is danger of obtaining moireefiects by using line half-tones since the meshes of the silk form a screen making of half-tone too. In addition, the silk screens are limited to smaller sizes on account of the cost of photographical line half-tone plates and are also limited to one or two colors since the regular color separation half-tone the silk screen process.

plates cannot be used in The half-tone silk screens cannot use finer line half-tones than 60 to '70, and are therefore not used very much for small work, while big reproductions for which to line half-tone would be perfectly suitable, cannot be made on account of the prohibitive cost of line half -tone plates of this size.

I have found that the photographical step can be eliminated and good results obtained by a new method involving few and simple steps. My preferred method is as follows The sketch or enlargement is placed underneath the silk screen sketch made on the pencil or other quite into detail in of shading with the easier. When the screen is placed direc suitable means.

and a pencil tracing of the screen by means of a lead I prefer to go order that the second step wax crayon may be made tracing is finished, the silk tly over a metal plate which is deep-etched to provide raised shading dots, stipple, lines, or any desired design. The silk, carrying the tracing, rests directly upon the etched projections of the metal plate. The easiest way to produce distinct and different 60 shades is to use several plates having the same dot arrangement, but the dots being of different size on each plate. The artist then draws, with wax crayon, the picture on the screen just as though he were drawing on Ross-board or any grained surface. Slight pressure with the wax crayon produces small dots or light shading on the screen, while stronger pressure produces larger dots. By slightly shifting the screen after each shading stroke, the number of dots can be increased until the area becomes solid black (or another solid color). The artist works on the screen long enough until the crayon drawing appears like the original although somewhat stronger in all values in order to be sure that enough wax is deposited on the screen.

After the drawing in wax has been completed, the screen is then prepared for printing by sealing all the open meshes in the silk with glue or some other suitable material. For example Le Page's fishglue, slightly or more thinned down according to the number of mesh used, together with dye or watercolor to make it better visible, and with a little glycerine to give it greater flexibility is now poured onto the screen around the edges and with a sharp and straight cardboard scraped over the screen in every direction. In this manner, the glue is forced into every opening in the screen but, because of the resistance of the wax to the glue, it does not stand on top of the wax drawing. After roughly drying, say for half an hour, the whole screen is washed with gasoline, turpentine, or other suitable solvent of the wax, and the wax quickly removed. Where the wax formerly stood, there are now fine openings varying in size. Since a glue screen is easily ruined by water, and is affected by moisture, it is advis'able to give the screena protective coat of silk screen lacquer. If desired, a coat of thin lacquer maybe sprayed onto the bottom of the screen. For a stock screen and for very large runs, it is desirable to harden the glue by applying formalin and allowing it to dry on the screen. The lacquer may be applied after the application with the formalin. 1 5

Corrections on the screen can be made quite easily beforethe lacquer treatment by brushing with stifi brushes on places where stronger printing is desirable, or by spraying thin glue on places where fewer openings in the silk are required.

When it is desired to print in several colors, the

foregoing process is modified slightly. The tracing is preferably made with ink instead of pencil. After the tracing is completed, the drawing is worked out over the etched plate in exactly the same way as described above, except that the drawing now includes only the portions of the original in one color. After the completion of the shading with wax pencil, glue is applied, the wax removed, and the glue hardened or covered with lacquer as described above. The printing is then carried on in the usual way. After the prints have been made, the glue is washed from the screen, leaving only the ink tracing thereon. Another color portion of the original drawing is then shaded in with wax pencil and the same series of steps employed to effect the printing of the next color portion. In this manner, the prints in several colors can be readily formed while employing the same screen. There is no limit to the number of colors which can be printed from one screen. By this method, fairly fine shading can be made with No. 10 or 12 silk, while finer silks like No. 15 or 16 produce shadings equal to photographic work on No. 20 silk or finer. The easy cleaning of the screen and the easier printing through coarser silk especially on large jobs are a distinct advantage. The drawings do not have to be reversed but can be exactly like the original.

I will now describe a modification of my process which gives greater accuracy in detail work. The process described above is the most practical for large work or where little detail is involved. However, where greater accuracy in detail is required, I prefer to use the following method:

Instead of drawing directly on the silk screen with the wax crayon, I place a sheet of thin good tracing paper or high grade tissue paper upon the original and make an outline tracing. The paper is then placed upon the etched metal plate and the drawing shaded in with wax pencil. By using a hard wax crayon and with the right pressure, every dot can be reproduced faithfully and clear. When all the shading is finished, solid masses or lines can be added by drawing on a smooth surface.

The next step is to render the wax areas and lines opaque in order that the wax drawing may serve as a negative. Upon a large sheet of white paper, I sprinkle gold bronze powder, or other suitable material, as evenly as possible over an area the size of the drawing. I then place the wax crayon drawing face down on the gold bronze powder. My next step is to take a lukewarm iron and iron over the back of the drawing. Very little heat is required since the warm wax softens at about 120 or 130 F. It is undesirable to carry on the ironing operation for a long time because this might cause spreading of the wax lines or dots. Adherence of the gold bronze to the wax renders the wax opaque and finishes the plate for exposure. The plate or negative is then exposed, just as in a photographic negative, to bring about its reproduction upon the sensitized silk screen. This latter step being old and well known, further description is believed unnecessary.

If desired, my method may be employed to form the design in half-tone upon a paper sheet and then a photograph may be taken of this drawing, and the photograph reproduced on a sensitized screen and plate, etc., in the usual manner. In this method, it is very desirable to use etched plates with dots or lines from two to three times, or greater, the size required, so that the reduction by photographing will eliminate all roughness or inexactness.

While in the above description, I have given specific examples of one method of carrying out the invention, it will be understood that the details may be greatly modified without departing from the spirit of my invention. The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible, in view of the prior art.

I claim:

1. A process for the purposes sets forth, comprising tracing the outline of a drawing upon a silk screen, placing the screen over a roughened plate having raised projections extending over its face, shading in the drawing with wax pencil on the plate-supported silk to produce a halftone effect, coating the silk with a wax-repellent material, removing the wax by means which does not remove the coating material, and printing upon a surface by forcing ink through said screen.

2. A process for the purposes set forth, comprising tracing the outline of a drawing upon a silk screen, placing the screen over and in direct contact with an etched plate having its surface covered with raised projections, shading in the drawing with wax pencil on the plate-supported silk, coating the silk with a wax-repellent mate-' rial, removing the wax, treating said coating material to strengthen it, and printing with said screen in the usual manner.

3. A process for the purposes set forth, comprising tracing the outline of a drawing upon a silk screen, placing the screen over a roughened plate having raised projections extending over its surface, shading in the drawing with wax pencil on the plate-supported silk to produce a halftone effect, coating the silk with glue, removing the wax, treating said glue coating to strengthen it, and printing upon a surface by forcing ink through said screen.

4. A process for the purposes set forth, comprising tracing the outline of a drawing upon a silk screen with ink, placing the screen over a roughened plate having raised projections, shading in a portion of the drawing with wax pencil on the plate-supported silk, coating the silk with a wax-repellent material, removing the Wax, printing upon a surface by forcing colored ink through said screen, removing the material on said silk, again placing the drawing over said roughened plate, shading in another portion of the drawing with wax pencil, coating the silk with a wax-repellent material, removing the wax, and printing upon a surface by forcing a different colored ink upon said screen.

5. A process for .the purposes set forth, comprising tracing the outline of a drawing upon a silk screen, placing the screen over a roughened plate having raised projections, shading in the drawing with shading-material on the plate-supported silk to produce a half-tone effect, coating the silk with a material repellent to said shadingmaterial, removing the shading-material by means which does not remove the coating material, and printing upon a surface by forcing ink through said screen.

FRANZ WEISS.