US1592265A - Process of making engravings - Google Patents

Description

Jul 13 1926.

J. S. GUNTERMAN PROCESS OF MAKING ENGRAVINGS Filed July 16. 1923 ffiZ'f/Z/OZI J hn. 5. flank/"man. 7% W X 117 War .6%

Patented July l3, i926;

outrun STATES PROCESS OF MAKING ENGRAVINGg Application filed July 16, 1923. Serial No. c51,saa

This invention relates to processes for making engravings; and more particularly to methods and means for accomplishing what is known as the staging of plates during the process of etching them.

As is well known in the engraving art, plates such as half-tone lates, are first etched somewhat lightly, and are then treated with an acid-proof material in those parts which it is desired to protect from further etching, and are then re-etched to attain contrast and depth. This operation must sometimes be gone through several times in succession; and in the past it has been the usual practice to carry out this staging operation entirely by hand. Consequently, the hand work requires a considerable amount of time and must be done with skill and care.

It is a general object of this invention to provide a process and a means whereby the staging operation may be accomplished quickly, and without requiring the services of a highly skilled engraver. Using my invention, an engraver can accomplish the staging operation in a few minutes, as compared with the hours that are sometimes taken in staging aplate in accordance with the old and well-known method. Thus, a most marked saving of time is effected; and, furthermore, my improved staging operation does not require the fine skill and judgment that the old operations have required.

I will now proceed to a detailed description of the process I have invented and of the substances that are used in the process.

In a half-tone plate that has been made from a negative taken through a half-tone screen of the usual type, it is well known that the darker parts of the plate are made up of dark cross lines with small openings between the cross lines, which openings are etched below the surface of the plate in the first etching. In the lighter portions of the plate, however, these small openings between the dark cross lines have so expanded as to obliterate the cross lines except at their points of crossing; so that in the lighter portion of the plate the surface, after the first etch, is characteristically a sunk surface with comparatively small uniformly spaced projections rising to the original surface of the plate, while in the darker portions the surface is characteristically the original plate surface with small uniformly spaced sunk spots. The transition from one condition to the other is of course usually gradual in the actual plate; but the figures in the accompanying drawings will serve to illustrate the general characteristics of the plate surface. Thus in Fig. 1 I show a greatly enlarged section of a typical plate; and in Fig. 2 I show a plan of the same. In these 1 figures at the left I show what is a light portion of the plate while at the right I show what represents a dark portion of the plate, with the intermediate transition between them. While I do not in these drawings attempt accurately to represent the actual surface configuration of the plate, the drawings illustrate the different characteristics of the plate' in its lighter and darker and intermediate portions. In Figure 1, the sunk portions A are shown to be of comparatively great extent in the lighter portions of the plate, while the raised portions B thereof are of comparatively small extent; while in the darker portibns of the plate the sunk parts A are of comparatively small extent and the raised parts (the parts that stand at the original surface of the plate) B are of comparatively large extent. In the intermediate transition (the parts forming what are called the half-tones of the picture) the proportion of raised and sunk surfaces is more nearly equal.

The drawings may be taken to represent the plate after its preliminary etch; and it is not necessary to explain in detail the procedure by which the plate is brought to this point of the process, as that is well understood by engravers. It is well understood how the positive film on the plate, after having been printed from the negative, is developed and the undeveloped parts washed ofi, leaving the developed emulsion over those parts of the plate that are not to be etched away. The plate is then put in the etching solution to etch away those arts that are not covered by the developed ardened emulsion.

A plate in this state does not have the necessary contrast between dark, half-tones, and high lights; and it is necessary to further etch the lighter portions of the plate so as to increase the relative proportion of sunk surface and decrease the relative proportion of raised surface. Whether only the lightest high lights are so re-etched, or the half-tones also so re-etched, is a matter largely within the judgment and discretion of the engraver.

I first take the plate, and, rubbing its surface with some suitable powdered substance, preferably a chalky substance like powdered magnesia, I fill all the parts of the plate below its upper original surface, so that I fill all of the sunk portions A and A. This is illustrated at C in Fig. 1; and it will be noted that I fill the small sunk portions as well as the large sunk portions. This is very easily done by simply rubbing the powdered substance over the plate with the hand. Then I form over the surface of the soetched plate, an acid, or etching solution, resisting film. Generally speaking, this may be done in any suitable manner or with any suitable substance; but I prefer to form this film by flowing over the plate a solution that will quickly dry and will form a film that resists the action of the etching solution. This film is shown at F in Fig. 1. Although there may be many solutions that will accom plish this purpose, and I have found several that will do it satisfactorily, the best solution I have so far used is one made up as follows: 1 quarts alcohol, 3 drams rosin, 6 drams shellac, 3 ounces benzol.

This solution dries quickly, forms a very good protecting film, adheres well to the surface which is to be protected, but at the same time comes off easily with the magnesia in those parts where I wish to remove it. The shellac here may be any of the ordinary kinds. I find that either orange or clear shellac does well. I also find that a solution of rosin alone in the alcohol or alcohol and benzol or a' solution of shellac alone with alcohol or alcohol and benzol, will 0 rate satisfactorily.

Havlng thus prepared the plate, the next step is to remove the magnesia and the protecting film from those parts of the plate where it is desired further to etch. As a practical matter, I have found that if it 1s desired to remove the protecting film from high lights only, a short rubbing with a fairly stiff bristled brush will remove the protecting film and magnesia from the sunk portions of the high lights without remov- 1ng the film from theraised portions in the high lights or from either the sunk or raised portions of the darker parts of the plate.-

On the other hand if it is wished further to etch out the half-tone portions as well as the high light pjortions of the plate, I find that a short ru bing with a block of belt, such for instance as an ordinary blackboard eraser, will not only remove the magnesia and the protecting film from the sunk portions of the high l1ghts, but will also remove them from the sunk portions of the halfton'es, leaving the protecting film in place over all the raised portions and over the relatively small sunk portions of the dark parts of the plate. It will of course, be understood that if the protecting film should be removed or partially removed, from the raised surfaces, that will not affect the final result, as those raised surfaces are protected by the hardened emulsion. It of course depends upon the pressure and length of time of rubbing to just what extent the magnesia and the protecting film are removed from the darker parts of the half-tones. The engraver, after a few experiences, knows just about how much rubbing to do in order to get desired results.

The function of the magnesia (or other kind of powdered substances used) is to form a granular backing for the film that covers the sunk portions; and it is because the film has a backing of this character in the sunk portions, that the brush or other rubber will take hold of the. film over the larger sunk portions and will remove it and the magnesia from the plate.

The plate, thus partially protected by the film, is again placed in the etching solution for further etching of the unprotected parts. After this etching has been carried to the required extent, the plate is washed; and the filming operation and re-etching may be repeated as many times as may be desired, to further etch any particular portions of the plate that may require further etching. All of this is a matter that lies within the juc gment and discretion of the engraver.

Each time the magnesia and the protecting film are applied, it is desirable that the plate be dried beforehand. It is also desirable to get as even a film as possible, and this is doneby pouring the solution freely and evenly over the plate, allowing the surplus to drain off at a corner or edge, and standing the plate up to dry. When the protecting'film is being partially removed, that is preferably first done with a fairly stiff brush or rubber, while dr and then after the dry brushing it is we 1 to wet the plate and scrub the plate well with a wet brush.

After the etching is completed, then the remaining protecting film and underlying magnesia are removed. In order to remove the film it is first softened or dissolved by using alcohol or a mixture of alcohol and benzol. A weak solution of muriatic acid, or a weakened etching solution with chloride of iron dissolved in it, also helps to loosen the protecting film. Then the late is brushed to remove the remaining 1m and remaining magnesia, and is then washed and dried.

The above described simple and quick operations are all that are necessary for bringing the large majority of half-tone plates to perfect printing condition. However, in exceptional instances, the operator may rub out the protecting film and magnesia from certain selected portions of the plate in order to get more than the ordinary amount of etching at those portions. Such things,

experienced engraver.

however, are well within the skill of an Having described a preferred form of my invention, I claim:

1. A process that includes filling the surface of a partially or preliminarily etched plate with a loose'filling, forming an etching resisting film over the surface of the filled plate and filling, removing the film and the filling from portions of the plate, and then further etching the plate.

2. A process that includes filling a partially or preliminarily etched plate with a finely divided solid substance, forming an etching resisting film over the surface of the filled plate, removing the film and the fillin substance from portions of the plate, and 't en further etching the plate.

3. A process that includes filling a partially or preliminarily etched plate with a finel' divided solid substance, forming .an etching resisting film over the surface of the filled plate, removing the film and the filling substance from those portions of the platethat have relatively larger areas of sunk etched surfaces, and "then further etching the plate.

4. A process that includes filling a partially or preliminarily etched plate with a finely divided solid substance, pouring over the filled plate a solution that comprises a drying liquid and an etching resisting substance in solution, thereby forming over the surface of the filled plate an etching resisting film, removing the fihn and filling substances from portions of the plate, and then further etching the plate.

5. A process that includes filling a partially or preliminarily etched plate with a finely divided solid substance, then pouring over the so-filled plate a solution of rosin and shellac in alcohol and benzol, allowing the plate and over the filling a film that resists action of an etching solution, and then brushing and rubbing the plate to remove the film and the filling substance from those portions of the plate that have relatively larger areas of sunk etched parts, and then further etching the plate.

7. A process of re-etching half tones on copper which consists in applying magnesia thereto, in removing the magnesia from the high lights thereof, in re-etching the high lights so exposed, and finally in washing oil the magnesia from every portion of the plate, substantiall as described.

8. A process 0 re-etching half tones on copper which consists in applying to its surface a loose ingredient, in then flowing into the plate a solution which renders such ingredient both hard and acid-proof, in then removing the said hardened ingredient from the high lights of the plate, in subjecting the plate to a re-etching acid treatment, and finally in removing the remaining hardened ingredient from the low lights 0 the plate, substantially as described.

In witness that I claim the foregoing I have hereunto subscribed my name this 29th day of June, 1923.

JOHN s. GUNTERMAN.

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