US1012762A - Method of producing printing-plates. - Google Patents

Description

A. VALENTIN & J. ZBRREISS. METHOD or TRoDUcING PRINTING PLATES.

APPLIOATION FILED AUG. 16. 1909.

Patented Dc. 26, l1911.

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` or relating to AUGUSTE -Unrrnn sirnrns -rArENT OFFICE.

ULENTIN, or 1 Ucl` Ux, Vnim or coUnisnvoIE, METHOD oF -PnonUcING PRINTING-PLATES.

lvpeciati f Letters fuient. Patented Dec. 26, l1911.

,/ Appucatiqpm'eg-August 1e; 190s. serial 513,072.

Toill whomi'itumwy concem:

f e it known that we, AUGUSTE VALENTIN,

a citizen ofthe Republic of France, `residing at Puteaux, Seine, France, and- ZER- Rnrss, a subject .of the German Empli'e, residing at Courb.evoie,Seine, France, have 1nvented certain: vnew :and useful Improvements' inl Methods fof- Producing` Printing- Plates, ofwhichthe vfollowing is a specifica- 13 uw,

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This inventinlrelates to-fimprovements V1n theproduction of printing plates. p I

In theI accompanying drawings 'Figures 1 to 9 illustrate the production of screens and-x FfigsalO tolli illustrate-the 'manner in which a printing plate is'etch'ed The process Y hereinafter 'described makes Ait possible to' obtain direct 1 on metal `1. Plates engraved in intaglio l frompositlve photographic line or half-tone originals.

, These'plates engraved in intaglio, reproduce, without any touching up, all the fine tones and all the half-tones of the positive original print. All the tones are constituted` by hollows the dimensions of which, as regards extension and depth, are in exact proportion to the different intensities .of tones.'

' It is a process which from the point of 'view of quality, has a double eiiiciency. An eiliciency produced by an extension of thehol'- `l0ws in proportionv to the intensity. of the tones, and an eliiciency produced by thel thickness of ink retained in the hollows, the depth of which is in proportion to diferillio -t e tenslty ofthe tones. The inking plates obtainedv by this process, can be efected simply by the use of an inking 'and wiping .system which enables the -ink re quired for the printing to be regulated acengraved relief for typographieprinting from v negative photographic line or halftone originals. i v

General description of the process for obtaining plates 'engraved z'n intaglio- A thin copper plate, wellplanedvand polished on one of its surfaces, is prepared, and on the whole surface of the said plate is spread a layer of the following solution: water 500 gr., b ichromate 'of ammonia 12 gr., sugar" 8 gr., gum arabic 110 gr., ammonia 9.9 drops. rlhe late covered with that solution is secure to a 'revolving support which :is first operated slowly and "which is manipulated uniformly distributed. Platesv above a gas` heating stove; giving oif a gentle heat which assists the drying. As soon as it is dried and cooled, theplate thus prepared I is ready .for beingppro'vided with a screen.

Thel screen is produced on `the whole surface of theplate photographically, by using as the original 'a net-work arranged in a peculiar manner, as will be -hereinafter described, andhaving one of the shapes vshown in Figs. 4, 6 and -7 according to the nature of the positive original to be engraved.v The pro'-A ceeding for thepurpose is as follows: The glass (orlilm) provided with'a screen,.is placed 'on the glass of a screw'printing press, withthe face providedfwith the screen,.in-A ward.` The 4copper plate "prepared, as already' stated,- is placed inrcontact with the screen. A thorough contactA between the screen'andth'e' plate is insured by the screws of the printing frame, which are tightened as much aspossibled vThe whole is exposedto the action of the sun, and when the action vor;

is considered sufficient, i the development is Y effected under Water lfrom a' tap. The'plate suitably developed, lwill have on the whole of its surface the image of the screeny constituted by a series of elements produced by the bichromate ysolution having been vrendered insoluble everywhere where the light acted, that is to say, under the transparent elements of the screen. These elementsare V equal to each other, and their geometrical sus centers are at the same distance from each other. As will be seen farther on, the degree of exposure must be calculated so as to give `to the elements of the layer, a vsuilicient reslstanceto the action of a mordantduring a certain time. They. must afterward crack when the action of the vmordant continues beyond .that time. As soon as the metal plate provided with the screen is developed, it is covered with the following solution: water`360 gr., beer 100 gr., bi-chromate of potash 15 gr., citrate of iron 1.3 gr., sugar 1 gr., albumen 120 gr., glycerin 2 gr., nitrate 100 of silver 5 gr. 4 The above must be -mi-xed and 125 gr. of flshglue. added to it.

The above solution is kept at. a tempera-` ture of about l17"' It is spread o n the whole surface 'of the plate on the revolving 105 support, and as soon as it isl dry, it is ready to receive the photographic image to be engraved. Thev image., is reproduced photographically in 'the printing frame. The

prepared surface of the pbite is placedinto the 'metal which Will be'hollowed out, akind continuing,

The corrosive action the Walls of the said cup Will be corroded, and the elements of the screen of the first layer reduced. Theperchlorid will'pass afterward through `the tones of an intensity immediately below the strong shades, 'and successively through all the tones in proportion to their degree Vof eX- ofv cup being formed.

. posure. The action of the mordant will be 6 5'quired for forming the image, being Aso to tion, the shape of the stopped by washing with Water as soon as it begins to attack the strong lights of the subject. At that moment, the portions cor-` responding to the shades, will be constituted by the elements of the screen reduced by corrosion to the state of granulated points owing to the cracking of the first layer (produced by the long action of the mordant), and separated by deep. hollovvs or recesses, While the portions corresponding to the lights, will be formed by the elements of the screen separated by slight hollovvs of small.

extent. The actionof the mordant produces a black oxidation of the metal, which enables'v v the engraving 0 y The image will appear in black proportionoperation to be followed.

ately as the second layer sion oretching plate, cleaned With inked and rinted.

For obtaining plates engraved in relief, for typographie printing, the process is the same as just described for making printing plates engraved in intaglio, but 1n that case negative .originalsare used. On the other hand, the cracking of the/elements of the screen during the vetching must be delayed and become apparent only in the strongest 'This delay of the perchlorid passing through the attacks the metal. -The corrohaving been completed, the potash, is ready to be about by an increase of-strength ofthe elements produced on the first layer. This additional strength is obtained by a longer exposure of the screen and by a- Weak burning y of the first developed layer.

Mechanical ewamz'mzton of the process.-

`As will be readily understood from the explanati'ons of the foregoing general descrip screen and the nature of the layer'. constituting the sama-play an mlportant part as regards the final result.

The constitution of the second layer res .those employed inl squares rendered absolutely say invariably fixed in accordance with .a

.could be obtained in practice. ,The researches of the applicants were chiefly 'directed, with regard to the said second layer, to the chemical com osition of the sensitive solution by means o which it'is possible to obtain, practically andin a thoroughly industrial manner, engravings Which-can be compared in; every respect to those produced by the layer of bi-chromated gelatin used in heliographic processes. The modification of the final result in accordance with the nature of the subjects and the nature of the negative or can therefore, Vbe generally produced only by the modification of the shapeofthe screen, of the nature of the screen layer and the density of the mordantused.,forengraving These various elements will fbe examined and in conclusion the result 6" their variations in the different cases ofD their use vwill be given.

Preparation of glass, without' any grooves and perfectly flat, is taken and With the methods usually Wet collodion or any other The glass thus prepared and rendered sensitive, is arranged asusual in the frame of a photographic apparatus provided with a screen-holder into which is placed a screen with check pattern, similar in every Way to similar process.

apparatus in accordancewith the methods generally used in photo-engraving, so as to produce, by exposure and o`n thedevelop- 4ment, on the Whole of the surface of the sensitive glass a check shown in Fig. 1, that pattern of the shape is to say, formed by opaque by an energetic intensification. Y These points are in contact with each other at the corners and are very sharply defined at the side of the transparent squares which separate them. The glass is covered With rubber, covered with collodion and rendered sensitive. It is then lreplaced in the frame ex-l actly at the point Where it` was at the rst exposure in the chamber. Exposure is again made by s uitablyarranging the screen and using for the exposure alarger opening in the lens diaphragm than was used for the first exposure thereby producing slightly on the whole surface newly rendered sensitive, shaded oft' or degraded points of the shape indicated in Fig. '2. The glass being during the second exposure exactly at the same place as it wasjduringithe first ex osure and it being of course understood t at the screen is also located precisely at the same place during the second exposure,pthe

positive originals employed,

screena-jA very good v then again.

prepared in accordance employed in the the mechanical engrav- .ing processes. The Whole is placedin the said degradation or shading oif will be ef- Fig. 5, a glass is 'occurring in practice,

`plete reproduction of half-tones,

fected at the transparent` portions' of the first screen, and completed at the center of the same portions in a point rendered transparent by a suitable reduction. The screen, obtained by the combination of the two superposed images produced by the two lay ers differently exposed,l as just described, will have the appearance shown in Fig. 3. Thev nal screen required for the following operations, will be obtained by producing from the screen thus made, a photographic counter-type which atv the development'will present successivelytransparent, shaded-olf p1' degraded and opaque elements shown in Fig. 4.

Possible modifications of the nature of screens foon their 'use n the different practical cases.-In the foregoingv examination of the preparation of screens, the simplest method of proceeding for obtaining normal screens, that is .to say, screens which are adapted to the conditions most frequently has been given. In certain cases where it is desiredto h ave a high degree of ine'ness, as well as a comit will be advisable to make other types of screens which, being more complete than those first described, will make it possible to produce on the first layer of the metal plate, a greater sensitiveness to the action of the mordant. Thus the screen previously 'described is again covered with a solution of rubber rendered sensitive, and exposed as before, replacing the round opening in the diaphragm by a square opening so as to obtain square points on the third sensitive layer of the plate, after a suitable exposure and development; .the geometrical centers ofthe square points will coincide with the geometric centers .of the round points formed on the first and on the second layer, and the screen will appear with three series of points of diiferent intensity and of different shape uniformly superposed Aon each other on the whole surface of the plate.

For making a screen of the form shown in ner with moist collodion or any other sensitive emulsion, and the glass thus sensitized is placed in the frame of the photograhpio apparatus, the network screen being arranged in front of the glass at a suitable distance, whereupon a round diaphragm with a small opening is placed into the object glass, and o n the pattern plate of :the apparatusv is placed a strongly. lighted white paper. vThe sensitized plate is-exposed by uncovering the object glass for about 2 minutes, the glass thus exposed isdeveloped, and there will appear round opaque points. The developed glass is fixed, washed and dried thenafter having been lcovered with a weak solution of rubs prepared inv thek usual maii-v on the whole surface ber is again covered with collodion and sensitized, then replaced intothe frame of the photographic' apparatus in order to be again ex osed behind the network screen than duringthe irst exposure), 'a roun dia hragm with a larger opening being use After a suitable exposure, there will appear, after the development, on surface of the glass round points superposed over the first one and of a larger surface, and a network'screen will thus be reduced, provided on the whole of itssur ac'e with fine opaque round points or `in the center of other roundpointsmore more transparent, that with two gradations. This screen having been produced thus the plate is again covere with a solution of rubber, with collodion and sensitized, then exposed in the chamber behind the network screen arranged as before, a square diaphragm being used for this exposure in order, after the development, to produce, on the whole surface of the plate,.square points touching each other with their corners, and

widely dispersed and is to say a screen (care being taken to move it a llttlesfarther away the whole l dots arranged the operation is continued, the sensitive layers being superposed and secured to each other by said layers show successively as above described: The rst, fine opaque round points obtained by using a round diaphragm with a small opening. The second, round points more widely dispersed and less opaque than the rst ones, and obtained by using a round diaphragm with a larger opening.` The third, square points touching .each other with their corners and` less. opaque than 1the preceding ones, obtained by using a square diaphragm. The.. fourth, square points touchingeachother well at their corners,

and leaving between them transparent square points with rounded olf corners, and obtained by using a square diaphragm with recessed corners. The fifth, points, the angles of which penetrate decidedly into each other, and which leave between themround transparent points, this form of dots being obtained by the use of a square diaphragm theangles of which are recessed considerably. The superposition of these different.

forms of screens on one and the same glass, will form the screen shown in Fig.

' As is well known, the points produced on a sensitized glass through a net -work screen, vary in shape and in distance from each other according to the shape of the diaphragm used, and: the distance of the network from the sensitive glass; it will thus be understood thatJ it will. be easy to vary to .an infinite extent the -forms of network screens, superposed in the manner described on one and the same glass. hand, it is 'possible to. givevto each of the superposed sensitized layers, diferentdethe weak solution of rubber. The

On the other n grees of opacity by reducing Vthe intensity after the development by means ofa solution of cyanid of iodin. Thus for the screens shown in Figs. 6 and 7 round diaphragms will be used, the openings of said diaphragms increasing with each of the sensitive layers placed on the same' glass, the

said layers being suitably treatedl after the development to produce lfinally a gradation lof intensity of the different forms of points that will have been superposed.

- It will' be evident that the screens can be constructed so as to give a larger area to the transparent elements as shown in Fig. 6, or

e sure of the screen,

,on the contrary, so as to .give .a larger area .1. Square elements distinctly transparent, and 2. Elements opaque at their geometrical centers, the opacity decreasing from' the centers to the circumference. When a screen is produced on the first layer by the expothere Will be produced on the whole surface of the plate a positive image of the screen, that is to say, there will be formed on the said surface square elementsdistinctly opaque and square elements transparent at their geometrical centers and decreasing in transparency from their center to their circumference the said decrease being however only slight, lso that nally there will be a great difference between the opaque squares and the adjoining ones. It is necessary to take another factor into account, in the formation of the screen, to witz-the opposition Abetween the Atransparentsquares and the opaque squares of the screenbeing very great, the limit marking the difference ofexposure, will follow distinctly a line only provided that theA thickness of the sensitive layer is zero. But in reality that is not the case, and there will Vbe formed a well known irridiation phenomenon (Figs. 8 and 9). v

In Fig. 8,. g is the screen, ethe thickness of the first layer and Z the source of light. Fig. 9 is plan of Fig. 8. A slight additional exposure, outside the periphery of the opaque square will reinforce the square on the'lwhole of its circumference following the outline n, and the plate will show after the development and drying, a screen layer which will have different degrees of exposure which will be4 equally repeated on the whole of its surface, at each geometrical center of the points which divide it'up. A. copper plate provided with a screen, will, therefore, be formed, which Vcan be .by the will present, if submitted to the action' of a mordant, a very great sensitiveness and will be capable of undergoing that action with a very special precision. Thissensitiveness graphically illustrated by Figs. 10 and 11. y

In Fig.' 10, e represents the first. layer, the different thicknesses of e representthe different degrees of exposure. l The dotted lines indicate the action of the accordance with the different degrees of exposure.

etching in Fig. 11 is a plan of Fig. 10, which shows l the different degrees of resistance to the action of the acid, due to the different degrees of exposure. Thus, the portion M will offer the main'mum resistance for a certain time, after which it will crack. The portion N will have a resistance between the resistances M and P. '-The portion P will have a resistance decreasing from N to' Q. lThe portion Q will have no resistance and will b e attacked as soon as the mordanthas passed through the second layer. If, -011 the other hand, the distance R, separating the geometrical centers of the resisting points of the layer, is varied by the use of different sus sizes of screen, it will be seen that if R increases, between spreadsl and reduces the number of portions sensitive to the action of the mordant`; while, on the contrary, if R decreases, the number of sensitive-portions increases. At the/limit, that is to say, when R becomes inthe scale ofl existing sensitiveness initely small, there willA be obtained .on the metal plate a layer having such a constitution that each of its points will present a complete sensitiveness lto all the tones, and the action of the mordant, regulated sensitiveness of the said layer, will produce on the metal plate an engraving which will reproduce, by its different recesses, all the fine-tones and tones of the subject. I

Preparation of the .second Zagen-As soon as the plate providedwithla screen, has been developed and dried, it is covered w1th volving support. As soon as it is dried, it is exposed under the positive print or original of the image to be engraved, and after a suitable exposure which varles 1n accordance with the subjects, it is ready to be engraved.

Engraving.-For the constitution of the two adjoining geometrical centers' all the half- Athe second layer which is put on on the refirst layer practice has shown the vuse' of a screen of the shape shown in Fig. 4;

1 g2g Aa solution of the following formula:

water 500 gr., bichromate 'of ammonia 12 gr., gum arabic 110, sugarS gr., and ammonia 9.9 drops, to be suitable. In these conditions, the etching is effected normally by the use of a' solutionof perchlorid of iron of 45 B. in the following manner :l

resented by the diagram of Fig. 12, the'dif-i ferentthicknesses of which represent the intensities of the tones, that isto say, the portion 6 represents the transparent por- .tions of the: original (the lights) Athe portions 5, 4, 3,2 the tonesof increasing intensity up to the portion 1 which represents the opaque portions. The perchlorid will pass first through the portions of the second layer which have been exposed the least, that is to say, the portions 1 correspending to the deep shades and will attack that is to say,f1n the center o of the points q, r, s, t (Fig.= 11) which will be hollowed out and will spread as vthe etching is con- 20 cessively through the portions 2, 3, 4, 5 and 6 and will successively hollow out the cen.

lv.`v The action of etching will continue to spread toward the periphery, and the hollow will assume the Ashape indicated by o. The etching continuing, the angles g, 7', s, t of the resisting 'points of the layer, will intersect each other, and the hollows cor'- responding to the tone 3, will spread to y. The hollows corresponding to the tone 2,

will spread out to m, the hollows correspond' ing to thetone 1 will be very widely spread and will leave between them only a wea point. Moreover, the etching in these portions having been prolongeehthe' first layer will crack, and the perchlorid, passing through the said layer, will granulate the surface of the points, and the finished plate i will have the appearance shown in Fig. 12. Special conditions determz'nmg, the 'use of thediferent shapes of screens, the nature of the #rst layer and .the density of' the m07*- dam to be used-Photographic prints required for producing engraved plates generally have 'different characteristics as regards their photographic qualities. The said different qualities will be defined with reference to three types of originals or printsldened in the following manner:

lst type. The difference of intensity between the lights andthe shades is normal, that'is to sa'y,the lights are transparent, and the shades strong Without opacity.4 The details are well defined. The original or print is good. 1 2nd xtype. The difference ofl intensity between the lights and shades is slight, that is v to say,

thejmetal 'everywhere where it is exposedv tinued. The perchlorid will then pass suc-l 'ond type).

the lights are not absolutely transparent, and the shades not very'strong, the details being deined. The print is gray.

3rd type. The difference of intensity between the lights and the shades is strong, 7 0 that is to say, the pure lights are transparent,

-the shades are opaque and the details are generally faintly'drawn. The print is hard.

In order to determine the variations to which must be subjected each of the three elementsl Whic can be usefully modified (shape of the screen, kind of the first layer, density ofthe mordant) in the different practical cases, let 'us examine first what will happen when the nature of the said 30 three elements .is normal, that is to say, such as it ought to be for obtaining a good result when a print of the first type is used.

In that case experience has shown that: the screen mustbe of the shape shown in Fig. 4; the first layer is given by the following formula1`water 500` gr., bichromate ofammonia '12 gr., gum larabic 110 gr., sugar 8 gr., and ammonia 9.9 drops; the density of thev mordant (liquid perchlord of iron) 40o B. These elements having thus been experimentally determined, let the result of using them with the three types of print described be considered. Assuming that.

for the purpose three copper plates are provided with a screen of the shape shown in Fig. 4, with a first layer of the normal formula, and all three comprising a second sensitive layer of the same formula.v

Figs. 12-14 show the action of the etch 100 ing on the three copper plates provided in the inann'er described with a screen of the form shown in. Fig. 4. These three plates comprise layers of the same kind, ybut they are exposed each under 'a different positive. 105

k' Fig. 12 shows the actionof etching on one of the said plates exposed under a positive which is good (first type). Fig. 14 shows the action of etching on one of the saidv plates exposed under a gray positive (sec- Fig.` 13 shows the action of etching on one ofthe said plates exposed under a hard positive (third type).

Figs. 12-14 comprise each three -Views connected by a brace. The upper lviews represent the tones of the positive, the different intensities of which are represented by the different thicknesses. The portions 1 represent the shades, and the portions 6 the lights. The center views are views in v plan of the engraved plates, the surfaces of the hollows being shown by black portions. The bottom views are sections on 'the line A-A of the engraved plates. They indicate the depth of the hollows correspending to each of the 'tones andthegradationA of the etching. Letthe first of these plates (Fig. 12) be exposed under a positive ofthe rstr type,

.that is to say,

u nder a very good posit1ve; the second un- 130 der a positive of the second type (Fig. 14)

' and the third under a positive of the third type (Fig. 13). Let the etching be done will be thethird to then 1n a perchlorid .of 40 B. By dividing up the action of the etching into three stages (first-stage: etching the shades; second stage; etchin half-tones; third stage: etching the lights, it will be seenthat in the first stage: vthe plate exposed under the hard positive will be first 'attacked in the shade portion. The plate exposedunder the good original will be the second to be attacked in the shade portion. The plate j' the half tones.' The plate exposed under the hard print or original, will be ,the third to 'be' attacked in the half-tones. In the third stage: the plate exposed under the gray original or 'print will be the, first to bel attacked inthe light portion. The plate 'exposed under the good original or print will be the second to be attacked in the,

light portions. The plate exposed under the hard original or print will be the third to be attacked in the light portions. In short, the plate exposed under the gray original print will be the last to be 'attacked and the first toA be finished. The action of the mordant is, therefore, exercised for a very short time; the

shades will not have had time to be suiiciently hollowed out, and the points will not be suliicien'tly reduced. Ony the other' hand, the cracking of the rst la er will not take place, so that, onbeing ed in, the plate will have a regular or uniform appearance. Inorder to lincrease .the eiect, 1t would have been necessary that at the shades the points yshould have been more reduced, that y'is to say, that the said points should have been at the smaller and less resisting. This would have been"insured b the use of a screen ofthe shape shown 1n Fig. 7, and byfffthe use for the -iirst-,la e'r of' a solution of smaller resistance. n the other hand, it

1s wellvvknown that, when the4 density of the perchlorid is great, it 'passes with greater and passes j th'rough it only in -the shade portions and up to a certain degree of exposure. .It will, therefore, be possible to utilize this property which, by the use of a perchlorid of suitable density will enable the shades to be`hollowed `outbefore attacking the half-tones and a suicient hollow and reduction of the points to be obtained.'

When thesaid result is reached in the shade portion, the etching will be continued by beginning of the etching' Athrough the second layer,

substituting for the perchlorid of'high den'- sity, a perchlorid o smaller density which will pass through the half-tones and hollow out the metal at the same time reducing the points. As regardsthe lights, the density of the perchlorid will be still further de- Icreased, and a plate engraved by gradation will be roduced, which gradatlon will increase t e effect by doing away with the yuniformity of the etching. For facilitatrst ing'the cracking of the layer in the shade portion, a solution of smaller resist` ance will be used for forming the said layer.

Similar considerations deduced from the preceding observations, would lead to show that when a hard print is usedrit is necesand the densities. of the mordants to be used for each of the three types of prints previously described, could be defined as follows:

Normal-orzgz'nal .or pmtt. -First layer: Screen of the shape shown in Fig. 4 (transparent elements equal to opaque elements). Solution of the following formula: 500 gr. of water, 12 gr. of bichromate of ammonia, 100 gr. of gum arabic, 6 gr. of sugar and 9.9 drops of ammonia. Etching. First stage: solution of perchlorid of iron of 40 B. Second stage: solution of perchlorid of iron of '38 B. Third stage: solution of perchlorid of iron of- 35 B.

Gray original or 'pmi- First layer:

Screen of the shape shown in Fig. 7 (transparent elements smaller than the opaque elements). Solution ofthe following formula: 509 gr. of water, 12 gr. `of bichromate of ammonia, 110 gr. of gum arabic, 8 gr. of sugar, and 9.9 dro s of ammonia. Etching. First stage: solution of perchlorid of iron of B. Second stage: solutifvp of perchloridof iron of 40' B. Third` stage: solution of perchlorid of iron-of 38 B.

Hard vowgz'nal .or print-First layer: A

screen ofthe form shown in Fig. 6 (transparent elements larger lthan the opaque elements). Solution of the following formula: water v500 gr.,ib ichromate of ammonia'12 gr., gum arabic .135 grl, su ar 10 gr., and ammonia 9.9 drops. vEtc ing. First stage:

solution of perchlorid of iron of 38 B. Secr ond stage: solution of perchlorid Vof iron of 34.6 B. Third stage: solution of-perchlorid iron of 34 B. f

General. applications of the procesa-It is `possible by means of this process to producev engraving' plates -for printing in several colors, whethertheoriginal single color `prints have been obtained by .any ofthe reproduction processes at present used, or

whether they have been obtained bythe processes of photographic selection lfrom nature 45 the second ditto in plate ditto or from originals in colors. It is, however, necessary to distinguish more particularly one of the most important applications' which makes it possible to produce from otDucos du Hauron,

- other words,'it will photographic color originals or prints obtained from nature bythe Lumiere processes print, three single-color printing platesA (-yellow, red and blue) engraved direct in 1ntaglio, which on beingprinted by the present process and registered onl one and the same vehicle (paper, fabrics, etc.,') will re-v produce all the colors of the positiveoriginal or print used. For obtaining this result, it will be necessary to prepare three copper tplat-es which will be provided with an iden- .tical screen in the manner described, on a first layerof the same formula. The iirst of these plates will be covered with a second layer orthochromatized for the yellow. The

second of these plates will be covered with a second layer orthochromatized for the red. Thethird of the .said plates will be covered with a second layer orthochromatized for the (yellow, red vand blue) will reproduce withblue. The first plate will be exposed under the original polychromatic print by arranging a violet screen on ing frame. The second plate.' will be exposed under the original polychromatic print by arranging on'the glass of the rinting frame a green screen.v The third p ate will be exposed under the original polychromatic .print by arranging on the glass of the printing frame an orange screen. In that way, exposed, the second layer on the plates being on each of the said plates will be'rendered insoluble,yin proportion to the intensity of the yellow, red and blue radiations, and on engraving thel'e will be obtained 0n the first plate single colorreproduction in yellow, on redand on the third in blue. The' superposed impressions ofthe said three engraved plates out anyx touching up, thezexact` image of the' color print or original used. In this kind of engraving and color printing the same perfection willbe obtained as in engraving and printing in black. It will also be possible to obtain from single-color or polychromatic originals black'or color printing plates of a subject in anyrsize byI applyingethe method of photographic projection 'to thef` present process.,

'We claim 1. The method of producing printing plates, which consists' in covering the metal plate with a sensitivelayer, then exposing the samerunder a screen so as to produce on.

vthe whole surface of the lplate square ele'- it forms a the glass of the printla-yer .to dry so that it forms a said plate the image lto 'be ammonia, exposing ments distinctly', opaque and elements transparentv at their geometrical centers which elements decrease in'transparency from the center to the circumference, then developing the said plate, covering the plate with a sensitive layer, allowing the said layer to dry so that it forms a ilm, vthen producing onsaid layer the image to be engraved by means of an exposure through an ordinary photographic original or print, and then subjecting the plate thus exposedto the action of a mordant.

2.The method of producing plates, which consists in covering the metal plate with a sensitive layer, exposing the same-under a screen so as to produce on the whole surface of the plate square elements distinctly opaque and elements transparent at their eometrical centers which elements decreasev 1n transparencyl from the center to the circumference, then developing the said plate, covering the, plate with a sensitive layer, allowing the said layer to dry so that film, then produc' g onsaid layer the image to be engraved y means 'of an exposure through an ordinary photographic original or print, and then subjecting the plate thus exposed to the action of a mordant consisting of perchlorid of iron having a density varying' between 34 and 45 degrees B. according to the intensity of the p otographic original or print used.

'3. The method of `producing printing plates, which consists in covering the metal plate with a`sen'sitive layer comprising bichromate of ammonia, sugar and gumprinting l arabic, exposing the same under a screen so as to produce on the whole surface of the plate square elements distinctly opaque and elements transparent at their geometrical centers which elementsy decrease in transparency from the center tothe circumference, then .developing the plate, covering the late with a sensitive layer comprising blchromate of potash, citrate of iron sugar and nitrate of silver, allowin the said then producing on engraved by means of an exposure through an ordinary photographic original or print, and then subjecting the plate to the action of a mordant.

l 4:. The methodof producing rintin plates, which consists in. covering t e meta Aplate with a layer consisting of suitable proportions of.water,-bi.chromate of ammonia, sugar, gum arabic and a few drops Vof the same under a screen soas -to produce on the whole surface of the plate square elements distinctly elements transparent at their geometrical centers which elements decrease in transthus exposed opaque and parency from lthe center to the circumfer- .f

" suitable prop ortions of water, beer, bi-

lthel image to be engraved by means of an exposure through an ordinary photographic original or print, and then subjecting the' plate thus exposed to the action of a mordant. v

5. Th method' of producing prin plates; which consists in covering the meta plate with a layer consisting of suitable proportions of water, bi-chromate of ammonia,

mon1a5 exposing the same under a screen so as' to produce on the whole surface of-the plate square elements distinctly opaque and elements. transparent at their geometrical centers which elements decrease in transparency from the center to the circumfen' ence, th en developing the said plate in Water,

covering the plate 'with a layer consisting of the image to be engraved by means of an exposure through an ordinary photographie original or4 print, and then subjecting the plate thus exposed to the action of a mordant consisting of perchlorid of iron having a density varying between 34 and 45 degrees o B.' according to the intensity of the photol graphic original or print used. sugar, gum arabic and a few drops of amv In testimony whereof We have aiixed our signatures, in presence of two subscribing witnesses..

- AUGUSTE VALENTIN. JEAN ZERREISS. Witnesses: l

JUL1N CAECRN, H. C. CoxE.

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