US1276599A - Process of and apparatus for etching. - Google Patents

Description

J. H. WEEKS.

PROCESS OF AND APPARATUS FOR ETCHING.

APPLICATION FILED APR. 1, 1916- Patented Aug. 20, 1918.

2 SHEETSSHEET I.-

J. H. WEEKS.

PROCESS OF AND APPARATUS FOR ETCHING.

APPLICATION FILED APR. l. I916- Paten'ted Aug. 20, 1918.

2 SHEETSSHEET 2- J'WSEPH H. WEEKS, OF BUTLEDGE, PENNSYLVANIA, ASSIGNOR TO OF DELAWARE COUNTY, PENNSYLVANIA, AND RAYMOND M.

PHIA, PENNSYLVANIA, TRUSTEES.

warns, or PHILADEL- PROCESS AND APPARATUS FOR ETCHIN Patented Aug. 2c, 1918.

Application filed April 1, 1916. Serial No. 88,362.

To all whom it may concern:

Be it known that I, JOSEPH H. WEEKS, a citizen of the United States, residing at Rutledge, in the county of Delaware and State of Pennsylvania, have invented certain new and useful Improvements in Processes of and Apparatus for Etching, of which the following is a specification, reference be ing had therein to the accompanying drawm My invention relates to electrical etching and has for its object the improvement of existing methods of etching in the manner hereinafter stated.

My invention is applicable to either of the two classes of printing plates known as relief and as intaglio, respectively, and by it plates of either class may be produced either for direct use in printing, or for making transfers which thereafter by any suitable method may be caused to reproduce pictures, illustrations, designs, etc. The invention is also useful in the production of plates for other purposes than printing, and is not limited to any particular metal, being applicable among others to copper, zinc, brass, steel, and various alloys of metals.

Very generally stated, my improved method comprises the following principal steps: (1') coating a metal plate with a so lution sensitive to light; (2) exposing the same photographically; '(3) washing the plate to clear away the unexposed portions of the film or coating, in the case of some metals, owing to the character of the electrolyte to be subsequently usefl, immersing the place in a special harde ing solution; (at) drying the plate; (5) heating the plate to a temperature suflicient to bake or enamel the image on the metal; (6) coating the back of the plate with an insulating material; and (7) electrically etching the enameled image on the plate by suspending it in an electrolytic solution and passing current through it as the anode or positive terminal of the source of current through the electrolyte to one or more cathodes connected to the negative terminal of the source, so as to carry away metal from the plate being etched.

In practising this method there are a number of subordinate and ancillary steps to be followed, as well as many details to be observed, all of which I shall endeavor to disclose hereinafter in accordance with the terms and provisions of Sec. 4888 of the Revised Statutes of the United States.

In practising this method, I have found it convenient to make use of certain forms of apparatus, and in the description it will be desirable illustrate certain operations which take place. TlllS apparatus and the said diagrams appear in the accompanying drawln s in whichigure 1 is a diagram indicating on a greatly enlarged scale the substantial difference between an etched plate as ordinarily produced by electrical etching and the etched. plate produced by my method.

ig. 2 is a sectional diagram showing a screen interposed between cathode to prevent the passage of sludge to the anode.

Fig. 3 is a plan view of a tank with a plate suspended therein, face down, and cathodes hung vertically upon Wires along the sides and ends of the tank.

Fig. 4.- is a longitudinal view of the same partly in section, showing cams and slides for raisin and lowering the plate in the solution while etching.

.Fig. 5 is an end view showing another form of cam arrangement and driving mechanism for moving the plate up and down.

Fig. 6 is an end view of still another arrangement of mechanism forraising and lowering the plate.

Fig. 7 is a diagram showing a modified arrangement for supporting a small plate while being etched so as to bring it nearer to the cathodes with consequent saving in current.

Fig. 8 is a diagram showing the cumulative value of the effect on each of the four edges of a plate suspended vertically in the electrolyte, and having its position changed periodically so that each edge rests in each of the four positions one quarter of the total time.

Fig. 9 is a diagrammatic plan view of a tank with the anode plate suspended face downward and the cathodes suspended vertically and extending almost completely around the inside walls of the tank and thereby almost entirely surrounding the 'body of the electrolyte between the anode or anodes and themselves.

to present certain diagrams to,

JACKSON S. WEEKS,

the anode and Fig. 10 is a similar diagram showin a tank in section, with the cathodes vertical.

Fig. 11 is a similar diagram showing the cathodes inclined.

Fig. 12 is a diagram suggesting by shade lines the action of gravity on a vertically suspended plate.

l ig. l2" is a fragmentary sectional view of a plate very much enlarged, showing how the underside of lines are etched clean and sharp.

Fig. tank with vertically around the inner walls, brushes adapted to move up and down over the faces of said cathodes, and a motor driven shaft. having cranks connected to and moving said brushes as the shaft revolves.

in the production of printing plates there are two kinds, known respectively as line plates and half-tone plates. Line plates are the reproduction of any drawing or print, or any subject where the original copy consists of white and black portions, such as a proof of a type form, sample of handwriting, pen, or pencil, or crayon, or stipple drawings, or drawings made with mechanical shading devices, or any copy which permits of the making of what is known as a line negative, that is to say a negative consisting solely of uniformly clear and uniformly opaque portions. Halt tone plates are the direct reproduction of objects or of drawings, prints, photographs, etc., photographed through a screen composed of crossed lines, grains, stipples, or a single set of lines. lhe negative made through such a screen is known as a halt tone negative.

For the production of intaglio printing and embossing plates in line work where the sunken portions of the plate are to corre spond with the black portions of the copy, a positive must be made from the line nega tive. This also applies to the production of relief plates where the result desired is a reversal of the ellect of the drawing, that is, where the black portions of the drawing are required to be the white portions of the print made from the plate.

Where, however, an embossing or reverse plate is to be made from a line plate or type form, or other similar subjects, from which a proof on transparent or semi-transparent material can he made, this proof can be used as a substitute for a positive in making the photographic image on the plate. For the productionot intaglio printing plates in half tone two methods of securing the positive are in use: (1) The making of an ordinary photographic negative without the use of a screen and negative through a screen, as previously described, which otcourse produces ahali tone positive, and ('2) the making of a halt tone negative through a screen and subsequently 13 is a vertical sectional view of a suspended cathodes then photographing suchphotographing that to produce a hall tone positive. There is also what might be termed a third kind of plate, which consists in parts of both line and halt tone negatives combined, either by duplicate exposures with and without the screen, by employing masking out methods or by stripping together of various line negatives or positives and various half tone negatives and positives, either or all onto one glass plate as the case may require. These are known as combination plates. l have designated these classes and kinds of plates so that 1 might refer to them herein as line, halt-tone, combination, relief and intaglio negatives, positives or plates.

in the production of any plate as described, whether tor printing purposes or other useful or decorative purposes, where the same are etched by electricity, and where the image on the plate to be etched is produced by photographic means, all other inventors and users of other methods known to me have found it necessary, before etching, to reinforce the insulating or resisting materials, on which the image is first obtained or formed by photographic action. The most practical of these methods involves a double reinforcement, making a triple coating on the plate, to wit, (1) the sensitized material which is acted upon by the light, the subsequent ink coating, and the final application of resinous or other powder. An examination of such reinforced prints in fine work will show a lack of smoothness on the edges and a lack of clearness and sharpness of minute detail. Vvhere the latter is very line and close together, in some cases a complete loss occins through the filling over action of these various layers and the melting on of the powder, constituting the final application. The rein forcement of such images also involves additional time. in my method I employ what is of extreme importance in the production of electrically etched halt tone plates, or halttone portions of combination plates, for either class of printing, an insulating or resisting image composed of a single film which remains upon the plate during and after the operation of etching and proving, and which is not affected thereby and is absolutely smooth and has a practically negligible thickness, and is insoluble in benzin, turpentine and diluted acids or other chemical etching fluid, such as a solution of perchlorid of iron, nitric acid, etc. lVhen the plate is presumed to be fully etched a proof on paper may be taken for examination, and it the effect produced indicates that the entire plate must be etched more, the ink of proving can be quickly washed off, as with benzin or other cleaning fluid. and the traces removed with a cleaning a-cic, such as a dilute solution of IOU . effects in such darken in intaglio plates, and 1n these por-g muriatic acid, or a solution of acetic acid with chlorid of sodium, -etc., so as to remove any light film left from the cleamng off of the ink and any film caused by exposure to the atmosphere. image film remains intact, and the late may then be subjected to further etc ing by electrical means, or, if desired, some parts may be stopped out with shellac dissolved in alcohol or other suitable resistant material to prevent further etching in such parts; but such stopping out may only be successfully employed where the portions stopped out and those portions desired to be further etched have well defined edges existing between them. Otherwise a decided and unnatural demarcation would take place in the final plate between such portions. The proof, after the first etching, or subsequent etchings (except in newspaper work), in practically every case in half tone, or the half tone portions of combina tion plates for relief or intaglio purposes, will indicate that some hand chemical etch ing is necessary in certain portions to produce the most artistic results, so as to lighten portions in relief plates, or

tions where there is not a definite edge or line of demarcation between, but which might be termed a blending from lighter portions to a darker tone. This hand etching by chemical means is of prime importance in the finishing stages of all fine half tone Work and is termed reetching. It is thereforeof great importance that the ma terial of which the image consists be capable of resisting the action of both electrical and chemical etching, and such an image I employ. The image which I produce fully withstands the electric etching, and is afterward capable of being successfully chemically reetched and is unharmed by proving operations.

A half tone plate containing an image reinforced with ink, or with ink and any of the known powders, is not capable of beinglocally hand etched to produce the effects demanded for high grade work, on almost all half tone plates for other than newspaper work. Where it is indicated that a further etching of such an ordinary plate is desirable, it becomes necessary with the reinforced image methods to restore the image which had to be removed for the purpose of proving, by a tedious method of rolling up with fatty ink and reinforcing with some kind of insulating powder which must be melted thereon. In applying the powder at this stage, it is extremely difiicult, and in some cases impossible, to brush or blow it out of the very small openings. If, however, these are not entirely free of such powder, the further etching of such openings will be prevented, and a spotty or mottled efi'ect During all of this the greater depth before this will be plate.

In line plates or what is known as line portions of combination plates, after a certain depth is attained, which is technically termed (in chemical bite or first etch, powdering with resinous or waxous powder is necessary/ A variety of such powders have been in use, for a long time, by photo-engravers and 1 others employing acid chemical means, to prevent the thinning of the lines by side etching, which would soon be followed byv under cutting, or under etching of the lines, and if carried to an extreme degree, would necessarily take the line away entirely, or if only to a slight extent, would interfere withthe duplicatlon of the plate by electro-typing or stereotyping. To prevent side etching and thinning of the lines after having obtained a certain depth, reinforcing the side of the lines must be done in four directions, whether the plate be etched electrically or chemically, and this I must therefore do in my electrical etching method, although I am able to obtain a becomes necessary than is possible in chemical etching. The procedure is, after covering the plate with a waxous or resinous powder, such as dragon blood or a powder composed wholly or in part of asphaltum, to constantly brush the powder in one direction to bank the same on one side of each of the lines, this being continued until the surplus powder is cleared from the intervening spaces. -The plate is then heated to melt the powder and insure its adhering to the plate. The operation of powdering and each time heating. is repeated three times, or until the powder has been brushed in four different directions, and heated after each brushing, that is, from the top to the to the top; from left to right; and from right to left; (but not necessarily'in' this order). It may readily be seen that in very small spaces, such as between lines that are approximately one fiftieth of an inch apart, the powder entirely fills the opening and this receives no further etching after the first etching, so that the depth of the plate in such fine portions, therefore, depends entirely upon the first etching. Herein Iv claim great superiority owing to the fact that my plate is 50% to 100% deeper than the old plates before the necessity for powdering arises.

After powdering more or less of a shoul der is produced, hence by getting my plate so much deeper in the first etching, the possibility of shoulders on the sides of the lines near the printing surface is entirely obviated. Shoulders it maybe added increase the difficulty of printing any plate.

Referring to the drawings, I shall first briefly describe the apparatus illustrated etching) the first bottom; from the bottom.

produced in the printing from such plate is shown at therein, and then proceed to set "forth in detail the steps in operation of my process.

in Fig. 1, A shows roughly in section on a greatly exaggerated scale the eliect of electrochemical etching by the ordinary methods. The depth of the etch or bite is not uniform. and the breadth of the face port-ions isreduccd. On the other hand the section indicated by B shows on an exaggerated scale the approximate results of my process.

Figs. 3 and i show the form and arrangementof a tank T and appurtenances for carrying out my processes. in these figures, projections Z on the inside of the tank carry a wire or rod 1/" extending around the entire inside of the upper part of the tank and having an extension terminal connected to the negative terminal of the source of current.

My cathodes t consisting preferably of carbon rods provided with metal caps and hooks at their upper ends, are hung from this wire. In Fig. 3 twelve of these cathodes are shown, but the ninnber is immaterial, so long as their combined surface is greater than the surface of the anode or plate to be etched. A liberal allowance in this respect is productive of good results. The anode o P, suspended face downward from a pair of rods t consisting of copper wire bent in Ushape at one end, and connected at the other to the positive terminal of the source of current, which is preferably a dynamo of low voltage, but may be any convenient and suitable source.

I find that a considerable advantage is attained by moving the plate slowly up and down in the liquid during the progress of the etching. When a large quantity of solution is employed, the motion can be dispensed with, but I consider it very desirable to thus gently agitate the anode. Mecha nism for producing this motion of the plate is shown in Figs, 3 and a and modified forms thereof in Figs. 5 and 6. In the first two figures, I show a shaft S beneath the tank, with its ends journaled in bearings secured thereto, provided with a pulley s at one end for attachment to any suitable driving means. Vertical slides a are provided on the ends of the tank which at their upper ends carry the wires or rods 2& and at their lower ends are slotted to slide up anl down on the shaft, with roller bearings s resting upon the surface of rotary cams s on the shaft. As the shaft rotates, the cams s raise and lower the rollers s and the slides a to which they are attached, thereby raising and lowering the wires 6 which play between guides 25 in the top of the tank. In Figs. 5 and 6 l have shown modified forms of motion tor this vertical agitation, the shaft in Fig. 5 being mounted on the side of the tank and carrying cams which work directly on blocks carrying the wires i while in Fig. 6 is shown a form of parallel motion, a pair of pulleys mounted'at each end of the shafts running along the opposite sides of the tank, carrying a connecting rod 25 having its ends pivoted on eccentric wrist pins on both pulleys so that it is raised and lowered as the pulleys ro tate, communicating the motion moreover from the driving pulley to its mate. Uther devices for imparting motion to the anode may of course be employed.

1 consider it novel and original with me to arrange the cathodes in the manner described so as topermit an even distribution of the current in all parts of the bath. 1 have hitherto worked upon the generally accepted theory that the anode and cathode must face each other in parallelism so that the passage of current from one to the other through the bath should be in line as nearly normal to both surfaces as possible; but experience has shown me that this is unnecessary, provided that the points of suficient surface and even distribution of current are taken care of.

"l he cathodes which it have used successfully are ordinary round carbon pencils similar to those used in arc lamps. "Other shapes and material can be used but I find these the most satisfactory. in operator should have a bunch of these carbon pencils at hand with wire hooks attached, because the cathodes in the bath collect sludge, becoming coated therewith; and as this occurs the operator lifts out the coated pencils, throws them in a bucket of water, and hangs on clean ones, the change of an entire set requiring in this way less than half a minute. The fouled carbons may be thoroughly cleaned by slight wiping.

in order to retard the collection of sludge, and prevent the same from falling into the bath, and perhaps being carried to the anode, I provide small cheesecloth bags and hang these in the bath, either as screens for all the cathodes, or as individual inclosures therefor. A screen of this general character is shown in Fig. 2. When such an electrolyte is employed that hydrogen is liber ated at the cathode, l place the cathode t i slightly above the bottom of the tank, and then place between it and the anode plate a screen-preferably of muslin, although it may be or" other material not too denseto guide the bubbles of hydrogen away from the anode. Otherwise these bubbles adhering to the face of the anode have a tendency to cause irregularity in etching. in Fig. 2 P is the anode and n represents the muslin or cheesecloth screen. This screen must be of such a character as not to possess insulating qualities and not to interfere with the "free passage or flowing of the electrolytic solution. in an electrolyte where a heavy coating: of sludge terms on the cathode'plate,

practice the till . effect on the imasa which would loosen and float around the bath when even slowly agitated, with danger of adhering to the anode plate, or at least necessitating the filtration of the electrolytic solutionI surround the cathode loosely as in a bag, with a material such as thin muslin or a couple of thicknesses of cheesecloth which catches all of said coating or sludge, and which neither insulates the electrodes nor prevents the passage of the solution. I should also observe that where considerable excess surface is given to the cathodes they do not coat so quickly, and the accumulation of sludge does not require such frequent removal. As a matter of fact, in some electrolytes the cathodes do not need cleaning at all.

For the solution or electrolyte in the tank,

may employ any one of a number of formulas, all well known to those skilled in the art. The regular electrotypers formula so-called, consists of sulfate of copper dis solved in water to make a solution testing 10 on the Baum hydrometer, with suficient sulfuric acid added to bring the hydrometer test to 15. This may be used, but I prefer certain formulas of my own, which I shall now state and shall hereinafter claim as a part of my invention Solution No. 1: Dissolve calcium chlorid in water until the solution registers from 5 (with heavy Baum hydrometer) to a point of almost saturation. This solution can be used alone, but preferably I add one of the following acids or combinations thereof: Nitric, hydrochloric, chromic, citric, salicic, formic or acetic. Other acids may be employed if desired. The proportion of acid as well as the strength of calcium chlorid vary with the character of the work to be done. It is obvious that with the stronger acids a smaller quantity thereof is required; and the stronger the calcium chlorid solution, the larger the amount of acid ployed. These acids increase the conductivity of the solution, which also varies with the strength of the chlorid solution. The acids also serve to keep the face'of the anode clean and bright.

Solution No. 2: This is made according to the foregoing formula, following the same remarks, but substituting sodium chlorid (common salt) in place of calcium chlorid.

Solution No. 3: This solution is made in exactly the same Wa and according to the same directions as KID. 1, but ammonium chlorid (sal ammoniac) is substituted for the calcium chlorid.

Solution No. 4: Dissolve sodium chlorid in water until the solution tests 5 to 20 Baum, and combine in proper dproportions a solutlon of ammonium chlori of from 5 to 20 Baum, adding any of the above named acids until the desired conductivity and anode are produced. In this solution, it is not advisable to carry the which may be emtreated at the same time,

strength of the initial chlorid solution beyond 20 Baum, as acid is-to be added.

As illustrations of solutions produced by these formulas, I may note the following:

All of the formulas thus given will keep the face of the anode plate clean and clear, free from films and coatings, so as to insure evenand uniform etching at all stages.

en using solutions in which sludge is formed, and especially when I use a solid plate cathode instead of the carbon pencils above described (although it may be employed with those also), I provide mechanical means for disengaging the sludge and keeping the cathode clean, consisting of a series of four brushes connected together as indicated in the diagram Fig. 13. These brushes are connected with a motor driven device preferably above the tank, whose cranks or reciprocating parts have a considerable amplitude of motion, so as to Work the brushes up and down over the cathode plates. The motor device is arranged so that several tanks can be operated at the same time. With this device, it is not absolutely necessary to move the anode up and down, because the movement of the brushes causes a sufficient agitation of the solution.

In order to lessen the quantity of solution required in the tank, andalso todraw the heavy solution flowing from the anode plate directly to the base ofthe cathode or cathodes, I and 4. This is geometrically shaped, preferably with triangular ends, sloping sides, and its longitudinal ridge lying directly under the anode plate. It is made of acid-resistant material or wood or metal coated 120 with the same and water-tight.

Fig. 7 shows a tank similar to that of Figs. 3 and 4, with a small plate P supported on a cross wire, one end of which rests on one side of the-anode terminal rod 125 it and the other end of which rests on the side of the tank. By this means the small plate is brought nearer to the cathodes, and a number of plates of this size' may be insert a filler shown in Figs. 3

time may vary with While I have found it very advantageous to hang my anode plate face down in the solution, it is also possible to get good results, as will be hereinafter pointed out, by suspending the plate vertically in the solution, provided certain details are attended to. One of these is the turning of the plate so that it shall be in each of four positions, one end up, one side up, the other end up, and the other side up, each for onefourth of the total time of etching. 'lhe effect of this is shown in Fig. 8 which represents the plate in four positions.

In Fig. 9 is shown a tank which may be similar in every respect to that in Figs. 3 and l, but in which the cathodes, instead of being carbon'pencils are solid plates hanging down inside the walls or around it. T his form of cathodemay be employed with the anode in either of the positions described. and if the brushes of Fig. 13 are employed, it is quite as effective and as easy to handle as the pencil cathodes.

Fig. 10 is a diagram showing the relation between the cathodes'and anode of Fig. 9. in cross section. In Fig. 11 which is a similar diagram, the cathodes are shown arranged obliquely, so as to bring them into closer relation with the anode and perform functions somewhat similar to those to the inclined face of the filler F in Figs. .3 and t.

111 Fig. 12 the short lines indicate gravity actionon the vertical suspended plate of Fig. 8 and make clear the reason why 1 C011? sider it necessary to turn the plate at intervals in the solution. 1 do not consider the vertical suspension as good as the horizontal suspension with the face down, but the reason for this is not derived from any theoretical considerations, but from purely practical ones. It is difficult for the average worlnnan to determine at the beginning how many minutes aparticular plate is going to require before turning, and the dithculty is not lessened by the factthat the the temperature and therefore with the season, and that some pieces of the same metal are softer than othersand etch more quickly. The great advantages possessed by the horizontal suspension, however, are also possessed in great part by the vertical suspension, provided that the plate is properly turned. The great desideratum in both cases is to facilitate the transit by gravity away from the face of the anode, of the heavier solution caused by the dissolving of the anode formed by the action of the anion, also all impurities which may be present, thus assuring cleaner and more uniform etching throughout.

As a modification of the cathode suspension shown in Fig. 11, l may suspend the cathode horizontally near the bottom of the tank, beneath the anode.

Having thus described the apparatus, it shall now proceed to the steps in operation.

The first step consists in coating the plate, copper, brass, steel, zinc, or other metals, or combinations of metals, with a solution sensitive to light, and drying the same. This solution may be varied somewhat as to the ingredients and as to the proportions of each ingredient, but the formula which 1 pave found to give good results is as fol- OlVS:

Gelatin 40 grains Ammonium bichromate grams /Vater 12 02.

This formula may be varied as for eX- ample I may use the albumen of 5 to 8 eggs; from 90 to 150 grains of rock candy, from to 250 grains of gum arabic; from 25 to 80 grains of gelatin. and from 50 to 150 grains of ammonium bichromate. I state these variations to enable those who desire, to experiment. It should be noted that fish glue may be substituted wholly or in part for the gelatin in the foregoing formula, and potassium bichromate may be substituted in suitable proportion for ammonium bichromate.

As an alternative formula for the enamel solution the following may be used:

Albumen of 6 eggs Gum arabic 200 grains Rock candy 120 grains Ammonium bichromate 70 grains Water 8 oz.

In this alternative formula gelatin or fish gluemay be added if desired, and the several ingredients may be varied as follows: albumen from 4: to 7 eggs; gum arabic from to 250; rock candy from 90 to ammonium bichromate from l0 to 150. Any one of the ingredients may be varied Without varying the whole, and this is true of both the formulas given. Potassium bichromate may be substituted in the second formula in suitable proportions for the ammonium bichromate. lhese formulas are original and will be claimed herein as a part of my invention.

After drying, the plate coated as described from one of the foregoing solutions, is exposed under and in contact with a negative or positive or other form of design carrier, to the action of sunlight or artificial light. Afterward the plate is immersed in water, and gently rocked for two or three minutes, until the unexposed portions are absolutely and entirely dissolved and cleared away. (in the case of some metals, owing to the character of the electrolyte to be subsequently used, the plate is next placed for about two minutes in a hardening solution Lemma enameling. This change in color to a brownish tone, is the test for pro or duration of baking. The surface of t e image is then very hard and cannot be damaged by the bare hands and is not easily affected by any handling. It is as smooth as polished glass and the edges of the lines, etc., of which the image is composed, are as sharp as in the negative or positive under whichit has been exposed. It is extremely thin, presenting practically no relief from the surface of the plate even when examined under a low power magnifying glass, but is an excellent insulator.

- The back of the plate is next coated with an insulating material, which may be chosen from a great variety, such as shellac dissolved in alcohol, a solution of asphaltum and parafi'in, or almost any waxous substance, to which has been added a resin or I maintain the asg haltum, or both.

he plate is then connected with the positive wire of a dynamo or battery and immersed in a suitable electrolyte, constituting the anode terminal therein. I have found it preferable and shall claim it as original, to

late horizontally in the electrolyte with t e face (the side containing the image) downward, as herein'before described.

For cathodes, where a single large plate, or a number of small plates are to be etched at one time, I use either one large cathode, or several smaller ones in diiferent parts of the tank, all connected with the same negative Wire, so as to fairly equalize the distance the current need travel through the electrolyte, and thus insure uniformity in the depth of etching of the whole.

During etching, an occasional interruption of the current is desirable, and in fact important, because it tends to keep the face of the anode clean, and assists in producing smoothness of etching.

It will be apparent to those skilled in the art that some sundry changes and modifications may be made in the apparatus, in the method and in such details as the formulas of the electrolyte, etc; Thus, I may employ plates of various metals or substances, to be etched, and I may employ divers metals or other substances instead of carbon for the cathode, without departing from my invention. I may also vary the formula for the enamel as stated in the paragraph commencing on line 105, page 6, or otherwise, and generally speaking, I contemplate all non- 1) coatin .steps: (1) coating the essential changes and modifications as fairly fall within the scope of the appended claims.

What I claim and desire to secure by Letters Patent of the United States is:

1. The process of etching plates for printing and for other useful and ornamental purposes which comprises the following steps:

the late with a solution sensitive to lig t; (2 exposing the same under a design carrier to the action of light; (3)

dissolving the unexposed portions of the coating or film; (4;) heating the plate to a temperature sufiicient to bake or enamel the exposed portions of the coating or film of the plate; (5) insulating those portions of the plate which are not to be etched; (6) immersing the plate in an electrolytic solution, and passing a current from the plate as an anode through the solution to a suitable cathode therein.

2. The process of etching plates for printing and o purposes which comprises the following plate with a solution sensitive to light; (2) exposing the same under a design carrier to the action of light; (3) dissolving the unexposed portion of the coating or film; l) immersm the plate in a hardening solution for a su cient length of time to harden the coating thereon; (5) heating the plate ,to a temperature suflicient to bake or enamel the exposed portions of the coating or film of the plate; (6) insulating those portions of the plate which are not to be etched; (7) immersing the plate in an electrolytic solution, and passing a current from the plate as an anode through the solution to a suitable cathode therein.

3. The process of etching plates for printing and for other useful and ornamental purposes which comprises the following steps: (1) coating the plate with a solution sensitive to light; (2) exposing the same under a design carrier to the action of the light; (3) dissolving the .unexposed portions of the coating or film; (4) heating the plate to a temperature suflicient to bake or enamel the exposed portions of the coating or film of the plate; (5) insulating those portions of the plate which are not to be etched; (6) immersing the plate in an electrolytic solution, and passing a current from the plate as an anode through the solution to a suitable cathode therein; (7 moving the anode only in the solution during etching and in a direction perpendicular to the surface being etched.

4. The process of etching plates for printing and for other useful and ornamental purposes which comprises the following steps: (1) coating the plate with a solution sensitive to light; (2) exposing the same under a design carrier to the action of light; (3) dissolving the unexposed portions of the coating or film; (4c) heating the plate r other useful and ornamental v to a temperature suliicient to bake or enamel. the exposed portions of the coating or film of the plate; (5) insulating those portions of the plate which are not to be etched; (6') immersing the plate in an electrolytic solution, and passing a current from the plate as an anode through the solution to a suitable cathode therein; (7) raising and lowering the anode only continuously in the solution during etching and in a direction perpendicular to the surface being etched and parallel to the direction of current flow.

5. The process of etching plates for printing and for other useful and ornamental purposes which comprises the following steps: (1) coating the plate with a solution sensitive to light; exposing the same under a design carrier to the action of light; (3) dissolving the unexposed portions of the coating or film; l) heating the plate to a temperature sufficient to bake or enamel the exposed portions of the coating or him of the plate; (5) insulating those portions of the plate which are not to be'ctched; (6) suspending the plate in an electrolytic solution in such position that the heavier solution formed at the surface of the plate and in the recesses therein in etching will tend to flow away therefrom by gravity, passing a current through the plate as an anode and through the solution to a suitable cathode therein and reciprocating said plate during etching in a direction parallel to the natural direction of flow of said heaYier solution.

6. The process of etching plates for printing and for other useful and ornamental purposes which comprises the following steps: (1) coating the plate with a solution sensitive to light; exposing the same under a design carrier to the action of light; (3) dissolving the unexposed portions of the coating or film; (a) heating the plate to *a temperature sufficient to bake or enamel the exposed portions of the coating or film of the plate; (5) insulating those portions of the plate which are to be etched; (G) suspending the plate in an electrolytic solution in such position that the heavier solution formed at the surface of the plate in etching by the dissolvingiof the anode will tend to flow away therefrom by gravity, and passing a current through the plate as an anode and through the solution to a suitable cathode therein; (7) periodically changing the angular position of the plate in the plane of the plate so that uniform and equal effects will be produced on all parts of the plate and in all directions during etching.

7. The process of etching plates for printing and for other useful and ornamental purposes which comprises the following steps: (1) coating the plate with a solution sensitive to light; (2) exposing the same under a design carrier to the action of light; (3) dissolving the unexposed portions of the coating on film; i) heating the plate to a temperature sufiicient to bake or enamel the exposed portions of the coating or film of the plate; (5) insulating thoseportions of the plate which are not to be etched; (6) suspending the plate with the face or design downward, and passing a current through the plate as an anode, and through the solution to a cathode therein; (7) moving the plate up and down periodically in the solution at right angles to the surface of the plate and in a direction parallel to the flow of current.-

S. The process of etching plates for printing and for other useful and ornamental purposes which comprises the following steps: (1) coating the plate with a solution sensitive to light; (2) exposing the same under a design carrier to the action of light; (3) dissolving the unexposed portions of the coating or film; (at) heating the plate to a temperature sufficient to bake or enamel the exposed portions of the coating or film of the plate; (5) insulating those portions of the plate which are not to be etched; (6) suspending the plate with the face or design downward, through the plate as an anode, and through the solution to a cathode therein; (7) mechanically removing substantially all deposits from the cathode during the process.

9. The process of etching plates for print ing and for other useful and ornamental.

purposes which comprises the following steps: (1) coating the plate with a substance sensitive to light; (2) exposing the same to action of light to produce a pattern thereon; (3) developing the image; (a) baking the plate to enamel the image thereon, whereby the portions of the plate'covered by the image are insulated and protected in a single film; (5) electrochemically etching the plate.

in testimony whereofl affix my signature.

i JOSEi l-l H. WEEKS.

and passing acurrent-

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