US1225477A - Process for producing half-tone engravings. - Google Patents

Description

. A. C. MURRAY.

PROCESS FOR PRODUCING HALF TONE ENGRAVINGS.

APPLICATION FILED IuN 22, 1915.

1,225 Patented May 8, 1917.

7, F/ LZ. 5

W1 T/VESSZS.

4 WWRCMI/RPA Y Max/Z783 I ARTHUR c. MURRAY, or BUFFALO, NEW YoRR.

PROCESS FOR PRODUCING HALF-TONE ENGRAVINGS.

Application filed June 22, 1915. Serial at. 35,732.

To all whom it may concern:

Be it known that I, ARTHUR O. MURRAY, a citizen of the United States, residing at Buflalo, in the county of Erie and State of New York, have invented certain new and useful Improvements in Processes for Producing Half-Tone Engravings, of which the following is a specification.

This invention relates to a process for producing half-tone engravings and has for its objects the bringing out of a more perfect definition of tone by using a paraffin or similar wax in place of a staging ink, which is now' in common use, and to greatly decrease the cost of producing high grade half-tone engravings, and also obtaining more accurate and uniform results than have heretofore been possible.

In order to obtain a clearly defined picture with a satisfactory tone range, it is necessary to makesuccessive etchings of different portions of the plate and to depend more or less upon skilled hand work. To properly understand my invention and its objects, the present general method of producin half-tone engravings will be briefly descri ed. a

The ordinary practice of the art is to first produce a half-tone'negative of the picture or object to be reproduced, and from this half-tone negative a positive is produced upon a metal plate by any of the well known processes, and the picture being in the form of raised spots. To make this negative, the picture or object is photographed upon 'a sensitized plate, there being a screen interposed between the lens of the camera and the plate. In making this negative there is produced upon it opaque and transparent spots all over the same, and these spots vary rela-- tively to each other in size according to the tone depths of the different portions of the picture or object to be reproduced in halftone. It is also necessary to make the area of the transparent spots in the negative, larger than if a positive to be printed from it were to have the original tone range, and so a greater depth of tone is introduced.

The reason for introducing this greater depth of tone is that if only the required tone is given, the dark spots on the high lights of the picture will be so small that in etching the plate, the side walls of these spots will be entirely eaten away before a suitabledepth for printing can be obtained.

After the positive plate has been obtained Specification of Letters Patent.

. Patented May 8, 1911?.

and a suitable acid resist formed on those portions of the plate which are not to be etched, the plate is given an etching for a certain length of time. This etching is What is known as a Hat etching, and brings the darkest portions of the picture to the proper tone, while the lighter portions of the picture are still of too deep a tone.

The plate is then put into the hands of a stager who paints up all the dark portions of the illustration or picture on the plate,

leaving open the high lights for further etching which increases the contrast in the resultant. impression from the plate, as the more etchin which a plate has, the lighter it becomes. Ilnless the half-tones or shading is protected by'a suitable acid resist, the plate becomes flat, losing the contrast between the highlightand shading. This staging is done by hand with the use of a brush anda flowing solution of printing ink, lithographic ink or other preparation which forms an acid resist. This is an operation that often requires from thirty minutes to two hours, depending u on .the size and intricacy of the plate an the quality of the work desired. i

more contrast between the shadows and high lights is desired, a third or fourth etching is made upon the plate." For the third etching, the deep shadowsand darker half-tones are staged or protected-by painting and so on for each successive. etching until the high lights are sufficiently etched.

In my process the plate is prepared for the successive etching operations after the first etch in a manner to obtain better results in a shorter time and without the skill necessary in the ordinary practice just described.

For illustration, the drawing accompanying this specification has Figure 1 to show a plan view of an enlarged etched half-t0ne plate, which has been completely etched in two operations. Fig. 2 is a cross section of plate on line AA of Fig. 1 after the first etch. Fig. 3 is a cross section of plate on line AA after the second etch.

i. In Fig. 1, the deep shadows are shown at the left and having a large connected black surface 8 with small white spots 7 representing depressions. These white spots or depressions 7 over distance 4:, gradually increase in size towardthe right until they become connected and form grooves 7 over The plate is now etched again and where distance 6, which increase in size to the extreme right and so form the highlights, while at the same time the connected black' surface 8 at the left has been broken up."

In Fig. 2, the wax 9 is shown held in the depressions 7 representing the deep shadows and middle tones over the distance 4 and wiped out clean in-the high lights or open spaces between the dots 8 over the distance 5.

After the second etch as shown in Fig. 3,

the depressions 7 over the distance 4 are the same size as in Fig. 2, asthey were protected by the wax 9 and the disconnected dots 8 in Fig. 2 are etched fine to 8 as in Figs. 1 and 3.

, My process consists of first making a negative and a positive and completing the first etch in the usual manner, then heating the plate and rubbing over it a block of paraffin wax, or similar preparation. The heat of the plate melts the wax, completely covering the plate with a wax film and filling up all of the etched portions.

ceeded with, which-'consists-of laying the plate on a flat surface and scrubbing inthe etching fluid with a bristle brush. y

When necessary further successive etches can'be made in like manner.-

.By my method, a more gradual changein tone value is giventhe plate by cleaning or wiping out the wax where a gradual or slower etch is desired between the dark shadows and the high lights.

is cleanly wiped out in thelargerpart of Then before thewax has had time to cool, the plate is rubbed over with a cloth and diagonally through The wax the grooves, or hi h lights, while still hot, and in the mid e tones, having smaller spaces, a slight coating of wax remains. Then during gradually cleans out the thinly coated portions or middle tones and they receive a proportionally less etch.

the second etch, the brush.

Having thus described my process, what I claim is:

1. The improved process of making halftone engravings, such process consisting in making a plate from a negative and giving it the first etch in the usual manner, then heating the plate and rubbing over it a block heated and removing the waxfrom the portion of said surface to be further etched, cooling. said plate and etching the plate while thus prepared. Q

A method of producing half-tone plates, which consists in preparing a flat etched plate, heating theplate and applying a coating of paraflin or similar wax to fill up the etched surfaces, cleaning out the wax from. the high lights and thinning out the waxfrom themiddle tones while the plate is still heated, cooling said plate and applying an etching fluid in such a manner as to give a full etchto the high. lights and to gradu'ally clean outthe wax in said middle tones and thereby give said middle tones a graduated etch according to their tone values.

In testimony whereof I have hereunto subscribed my name inthe presence of two subscribing witnesses.

' ARTHUR O. MURRAY.

W'itnesses: 1 i

ANDREW T. BEASLEY, LUCIAN C. JACKSON.

Images