US865276A

US865276A - Art of etching.

Info

Publication number: US865276A
Application number: US23062004A
Authority: US
Inventors: Emanuel Spitzer
Original assignee: Individual
Current assignee: Individual
Priority date: 1904-10-29
Filing date: 1904-10-29
Publication date: 1907-09-03
Anticipated expiration: 1924-09-03

Description

EMANUEL SPITZER, OF MUNICH, GERMANY.

ART OF ETCHING.

' Specification of Letters Patent.

Patented Sept. 3, 1907.

Application filed October 29,1904. Serial No, 230,620.

To all whom it may concern:

Be it known that I, EMANUEL Srrrznn, a citizen oi Germany, residing at Munich, Bavaria, Germany, have invented certain new anduseful Improvements in the Art of Etching; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it 'appertains to make and use the same.

My invention relates to the art of producing etched objects and in particular to, the manufacture of photomechanical printing plates or surfaces.

The object of this invention is to produce by a simplified photo-chemical and mechanical method etched tion offers great advantages for the etching of reproductions from autotypic reticulated plate (screen) pictures,

from hand drawings, wood cuts, copper plate and gravings and the like, and in particular where it is desired to reproduce niceties of reticulated plate effects (screens) not obtained heretofore.

The essential feature and the novelty of the present invention consists in exposing directly to the action of the etching agent, the copy of an original which is pro duccd in-the sensitive coating or layer of the object to be etched, said original being, for instance, a drawing or any suitable photographicnegative or d'iapositive or other original capable of being copied. In other words, the copy is introduced into the etching bath directly, that is to say, in the state of hardness acquired through the exposure to the light, without such accompanying or'previous use of artificial protecting and hardening processes being necessary as'rolling'in or melting on of asphaltum dust upon the coating orlayer, enameling, or similar means of procedure. In this process great attention has to be paid in the first place, to the retaining of the. porosity of the 'parts sometimes extraordinarily fine which have remained unexposed to light between the exposed elementary divisions of the copied picture in the'copying layer so that these parts or passages allow the passage of the etching agent; and secdifferent parts oi'fer in different degrees resistance to rial during the etching process, care has to be taken that those places which are becoming developed are not attacked too niuch or entirely spoiled. This object may be accomplished in a most simple manner by allowing the deposits of the etching process, the etching slime or sludge, to remain on the'already attacked places, the etching slime protecting the places covered thereby against any further excessive action of the etching agent and thus against spoiling and destruction of the etching.

The process may for instance be carried out as follows: To the well cleaned plate or other object to be etched, a coating of a substance, sensitive to the action of light, such as chrome albumen, chrome gelatin, or the like, is applied. This may for instance be effected by putting the plate, before or after pouring on the solution, upon a centrifugal apparatus, in order 'to produce by rotation and simultaneous warming, a thoroughly well dried copying coat or layer which is as uniform as possible and free from grain.

In the manufacture of the copying coat or layer, the wrinkling of the same, similar to that used heretofore in .phototype work, should be avoided by all means, this wrinkling having been tried by several experimenters ior photomechanical reproductions with but only slight success, in as much as s'uch'an arificial graining interferes with the permeability of the pores to acid,-and also with the desired action of the acid on the elementary divisions. vDusting and melting asphaltum dust grain on the etching plate, as hitherto used particularly for engravings, should likewise be avoided, as well as the admixture of any substances to p the sensitive layer, which would produce a firm clearly defined grain in the same. Upon such a smooth, and

as nearly as possible uniform ungiained layer, any

original which admits of copying, such as a drawing or any photographic negative or diapositive (half-tone, reticulated (screen), line drawing, Rontgen rays 01 other kind) is copied. It is useful to determine the required degree of copying by means of a photometer. If the copy is too faint, the etching of the plate is easily spoiled or over-etched, in the case of the copying having been carried on too far, the permeability of the pores to acid is'impaired as well as the aforesaid capability of the elementary divisions to become progress- .ively etched. This capability to become progressively ceived, so thatthe entire copy will not present a thorough hardening of uniform strength but a progressive a progressive resistance to acids varying in degree. To

this progressive resistance varying in degree corresponds a proportionate progressive etching of the material, so that in the etching process here described, ,the

etching itself will proceed as follows :The copy on the object to be etched, obtained according to the directions heretofore pointed out, after being washed and dried if desired, is exposed, without the necessity of using any additional protecting means, to the action of an etching agent and particularly an etching agent which will have a hardening action on the gelatin or other coating, such as chlorid of iron or nitric acid with 1 alcohol 0. the like, the etching being finished in one or more baths .of different concentrations in accordance with the richness in half-tones'or with the purposes for which the plate is intended. In the case of copies fronrstrong negatives for instance, four or even five baths may be used. It is well known, that as regards the selection of the kind of etching baths and as regards the concentration and the temperature of the same, a variety of conditions has to be taken into account and the etching operation itself requires a certain delicate and artistic sentiment besides experience and training.

In as much as in this etching process, the dividing passages which have remained unexposed to light and which are between the exposed and consequently hardened elementary divisions, are unprotected against the action of the etching agent, the latter will penetrate through these dividing passages first of all, and will attack the material of the object to be etched at these places. This beginning of the etching process takes place at those parts of said object which were least exposed to light, because they are fewer and smaller elementary divisions and wider dividing passages present in these places as contrasted with the strongly lighted portions, in which, on the contrary, the elementary divisions are in excess as compared with the dividing passages not exposed to light and not hardened While in this manner the'etching of the dividing passages which have not been exposed to light proceeds, and while the etching cavities or sockets become hollowed out and the small cones form, the heads of which constitute the elementary divisions or minute (microscopic) particles of the picture, the already mentioned capability of these elementary divisions to become progressively etched will become apparent after a while in correspondence with the progressive hardening'of the same which had taken place. The small particles or points at the places least exposed to the light, with only a small head of hardened chromate layer are attacked very readily and the parts of the object to be etched just below them begin to be etched. This etching action is now taking place in such a manner that at the termination of the etching process this wearing away is most pronounced in the case of the parts which have been less exposed to light, while it is least pronounced in the case of the parts, which have been more exposed to light, and by these means the proportionate deepening ofthe elementary divisions or minute (microscopic) particles is produced. This etching action would however finally become excessive in cases in which delicate results are desired, unless the etching product'(slime or sludge) formed simultaneously in the process, which in such cases should not be removed by brushing out or the like, protected the small heads beginning to be attacked from further' action. This progressive etching action which is the characteristic feature of the present invention, may be varied to meet the various purposes intended and it may even be so delicate that it is hardly perceptible to the naked eye, and yet it is eflicacious for use, especially for printing purposes. In the case of a printing block recommendable to avoid washing and then drying the copy after exposure to light, but to introduce it, on'the contrary, directly into the-etching bath. The washing out of the copy, for the purpose of removing the chrome,

and the subsequent drying, causes a coarseness in the division of the picture; wherever this'coarseness is desired, in the case forinstance of coarser reproductions, the washing out anddrying may take place before the etching.

Another novel and important auxiliary means for Y assisting in bringing out the niceties of a picture in accordance with the present invention consists in subjecting the etching bath with the object to be etched contained therein, to a gradual and progressive warming or to a gradual and progressive-cooling. By reason of this gradual change of temperature of the etching bath, a progressive dilution or thickening respectively of the acid is produced. The more liquid the acid is, the more delicate are the pores of the copying layer which it is able to permeate; and the larger the pores are, the more concentrated and consequently the more viscous should the acid be, in order to etch to a sufii-,

cient depth. Thus the progressive warming or cooling of the etching agent serves the same purpose as an infinite number of baths of continuously varying concentration. The gradually progressing warming is', for instance, effected by introducing a copy which, has been produced on the plate to be etched in accordance with the explanations given above, into an etching bath which appears suitable for the first permeation,

such as chlorid of iron of about 42 degrees, (or more or warmed bath is taken, the deeper are thefurrows of the etching; hence for printing blocks which are intended for printing inrotary presses, stronger baths will for instance have to be used at the beginningof the progressive warming than in the case of printing blocks which have to be used for printing in ordinary printing presses for more delicate efiects. It is not possible to fix a degree of concentration which would be suitable for'all cases, in as much as the selection of the paper, of the printing ink and other conditionsare also of great influence in determining the depth of the etching required.

The gradually progressing warming, is effected by placing the etching bath or baths employed into a hot or gradually heated sand bath or water bath or by any other gradually operating warming device, until the image on the object contained in the etching b'ath appears etched down to the nicest details; the object is then taken out, cleaned and made ready for use.

A progressive thickening of the acid which is desirable for some purposes is produced by placing the etching bath of a certain concentration, of about 40 or 42 degrees Baum for instance, or more or less, with the plate to be etched contained therein, in cold or gradually cooled water which if desired, might be cooled with ice, or by using any other gradually operating cooling device.

A further novel and important auxiliary means for assisting in bringing out the niceties contained in the original in accordance with the present invention, con

sistsin submitting the object to be etched to an etching bath the concentration of which is gradually lessened by introducing into the etching bath more or less slowly an acid of a lower degree of concentration. If, for instance, the object to be etched has undergone part of the etching process in a bath of 'iron chlorid of say 42 Baum, a dilution of iron chlorid of 41, 40, 39 or less degrees Baum is more or less slowly introduced into said bath. This more or less slow progressive reduction of the dilution of the acid of the etching bath pro duces similar effects, eventually even to a higher degree, as the gradual and progressive warming described above. i

Having thus fully described my invention, what I claim asnew and desire ,to secure by Letters Patent of the United States is:

1. The process of etching, which consists in applying directly tothe surface of the body to be etched a sensitized coating, then photographically printing an image upon said sensitized coating, and then exposing directly all portions of the surface of the sensitized coating to the action of an etching agent.

2. The process of etching which consists in applying directly to the surface of the body to be etched a sensitized coating, then photographically printing an image upon said sensitized coating, then exposing directly all portions of the surface to the sensitized coating to the action of an etching agent, and leaving the deposits formed by the etching action undisturbed until the completion of the etching action. a

3. The process of etching which consists in applying directly to the surface of the body to be etched a sensitized coating, photographically printing an image upon the.sensitized coating, introducing said body to be etched into an etching bath and regulating the etching operation by modifying the temperature of the bath.

4. The process of etching which consists in applying directlyfto the surface of the body to be etched a sensitized coating, photographically printing an image upon the sensitized coating, introducing said body to be etched into an etching bath and then into progressively modifying the temperature of the bath to regulate the etching.

5. The process of etching which consists in applying directly to the surface of the body to be etched a sensitized coating, photographically printing an image upon the sensitized coating, introducing said body to be etched into an etching bath and introducing additional etching fluid of a lower degree of concentration duringthe etching'operation, whereby the etching bath is progressively diluted.

6. The process of etching which consists in applying directly to the surface of the body to be etched a sensitized coating, drying said coating by centrifugal action, photographically printing an image upon the sensitized coating, and directly exposing all portions of the surface of said coating to the action of the etching agent.

In testimony whereof I hereunto aflix my signature in the presence of two witnesses.

EMANUEL srrrzn'n.

Witnesses PAUL PinLIPI'soN, Unrssns J. Brwa'rsn.