US1325890A

US1325890A - Lithography

Info

Publication number: US1325890A
Authority: US
Publication date: 1919-12-23
Anticipated expiration: 1936-12-23

Description

l.. FREUDER. LITHOGRAPHY. APELICAUON FILED Nov. 2e', 1913.

Patented Deo. 23, 1919.

W/ TNESSES lof which the following is a specification.

sirarirs PATENT OFFCE' LEO raEUDER, or BROOKLYN, NEW Your.

LrrHOGRerH-r.

recaen.

To all whom it may concern:

Be it known vthat l, LEO zen of the United States, and a resident of Brooklyn, in the county of Kings and State of New York, have invented certain new and usefullmprovements in Lithography,

This inventionrelates to lithography. 4According to the usual processes in lithog raphyl hitherto employed, a key plate has to he prepared by the lithographie artist by carefully reproducing every line, shadow and tone of the original.

This is accomplished generallyby making a series of dots with a pen, known as stipple work. Where the shadows are deep the dots are large and close together;

a very laborious and tedious operation requiring often a month o r more to turn out y the plates for tlie'pressl vInsome classes of.

. roughened portion of hand work the surface of the key plate or stone is and a crayon is-used intsead of the pen. This also ,requires a` lot of very careful hand workI andhas the .disadvantage ofthe difficulty with which impressions are taken from a stone so prepared. Thus, the keystone itself has to be used asthe press stone. A most prohibitive as the cost` of printing is too high unless aiiumber of impressions are taken on the press stone so as `to make a number of prints at each operation of the press.

llith vthe advent of lphotolithography some of the-hand work ofthe lithograpliic artist hasbeendispensed .withvbut a great work still remains, and, moreover, a disturbingelement is introduced in the form of the screenedl negative. The tints in the picture to he reproduced are broken up into a seriesofdots through the yaction of the screen, and thus in places' where the high lights are found there are dots to .be taken out and in the shadows there are 1n the half tones appear very mechanical and detract considerably from the artistic FREUDER, a citiat the intermediate tones they Vdots are smaller and farther apart. This is ln' smallerl work this process is al'v Speciicatioxi ofnlLettei-s Patent. Patented @go 23, 1919 Application filed November 26, 1913. Serial No. 803,123. i

eect as compared withthe original to be reproduced. There can be no gradual gradation of toiie as found in all high grade ,artlstic work. The sensitizer used is asphaltum or -hichromate- Tf the plate is a little over exposed or under exposed itis spoiled and must be thrown away and new plate printed. Moreover, these sensitizers are otherwise more or less uncertain in Vtheir action.

The present invention has for its principal object to provide a process in which all hand work requiring a lithographie artist or finisher is dispensed with, the screen is eliminated, the results are absolutely uniform and certain, while the quality of the, work is superior to that produced 'b the best of lithographie artists. The di ferent tones are produced through a grain which is more open or close according to the tone values and the minutest graduation in tone is faithfully represented with the utmost accuracy. The cost of producing the printing plate is reduced very greatly and the time which it takes to prepare the plates ,v from the copy is a small fraction of the time it takes with the ,processes known hitherto.

'The various further objects'and advantages will appear inore fully from 'the detailed description, andthe features of novelty will be particularly pointedout in the claims. v

Tn the accompanying drawing.

Figure 1 is a diagrammatic view illustrating on an enlarged scale the' characterv of the grain produced..

Fi 2 is a diagrammatic view illustrating t ie manner in which the impressions are taken from the key plate uponthe press plate.V

Preparation of the ceg/ plate. The material which T use for my key plate may be. any of theI materials now used such as stone, glass, zinc or aluminum and in fact, any other suitable flexible material such as linen or rubber. The plate is first coated with a substratum of a suitable adhesive substance such as sodium silicate dissolved in ten parts of a solution having albumen in a l 1. A gelatinous or gummy organic subable time without deteriorating.

stance sucl as or the like.

2. A sensitizer, preferably potassium bichromate or ammonium bichromate.

3. An agent which expands upon absorption of moisture, preferably calcium chlorid. This solution is sensitive to light only when dry, otherwise it'is not sensitive. It can therefore .be kept in stock for consider- I have lfound that the best proportions for the coating are as follows: f

Solution l: 1 part ofgelatin in 10 parts glue, gelatin, dextrin, sugar,

of water. l

Solution 2: 1 part .of bichromate and 1 part of calcium chlorid in 10 parts of water.

These solutions are kept separate and are mixed only immediately before being used upon the plate. lVhen the same are to be applied, Iadd 380 gm. of 'Solution l, 90 gm. of Solution 2, the mixture is stirred well, heated to a temperature below boiling point, filtered and then the plate maybe coated. The latter is then placed in a heating oven, particularly constructed for the purpose, and dried. It isnecessary that during the `drying process, the Vplate be lprotected from air currents, as a slight disturbance is liable to cause a ripple on the. surface of the plate which may appear later on the work. The temperature to which the plate is subjected in the oven depends upon the fineness of the grain desired in the work. In the usual run of work, the best grains may be obtained between temperaturesof 50 and 60 C. At or below 50, the grain is finer, at higher temperature the grain is coarser. The plates so prepared can be 1stored and, kept for twelve or fourteen days without deterioration in their actin'ic properties.

When the subject is `to be reproduced, as-

suming that` a suitable plate is had in stock,

the first step is to make a photographic negative or a number' of negatives, if the subject is to be reproduced in colors, using the well known. color filters. The negative is then putin a printing frame, the coated plate placed onA top of the same and exposed through the negative tovlight from three. to fifteen minutes according to the strength of the source of light. When the plate has been suiiiciently exposed, it is removed from the frameJ and washed in water until all the .bichromate is washed out, leaving an image of a brownish color upon the plate. If'the plate is a. little over or under exposed, it will do no harm as this maybe compensated for by the degree of inking in the further manipulation. After the bichromate is washed out, the printing quality of the plate is improved as follows: The plate is leveled and covered with a solution consisting of one part water, on@ part glycerin and a small amount of sodium chlorid according to the humidity of the air and the quality of the gelatin used in the plate. To about 225 gin. of a solution of water and glycerin, I add, under ordinary conditions, about 2 gm. of sodium chlorid. The plate is allowed to soak in this solution from 15 to 30 minutes or more according to the quality of the gelatin and the degree of exposure. The moisture is then taken off with a fine sponge and the plate is inserted in the same oven in which it was previously dried and subjected to a heat of 50. C. until the plate feels somewhat tacky, whieh occurs usually within twol to five minutes. The heat is then turned off, the plate is cooled and the same is ready for making off-sets upon the press plate.

When the key plate is inked with the usual `lithographie ink and a proof taken, it is found that the surface is broken up into a grain formed by sinuous interwoven somewhat broken lines having a flaky appearance. Referring to Fig. 1 the upper square shows on an enlarged scale the. character in the darker and intermediate tones and in the lower square the lighter tones and the high lights. It will be noted that a series of sinu- .ous lines 10 are formed from which radiate needles or tendrils 11. The general size of the grain depends upon the degree of heat to which the plate has been subjected while the grain, itself is produced by the expansion of the calcium chlorid in absorbing water. At the portions of the plate which have seen a lesser amount of light, the gelatin is comparatively soft and permits the moisture to percolate absorbed by the calcium chlorid. The latter in absorbing the water expands and thus breaks up the hardened gelatin into the grain described. `Where the plate has seen more light corresponding to the shadows of the subject, the gelatin has become so hardened that vless water will be absorbed and will also to a greater degree resist the force tending to break it up; thus the grain is close, consequently printing darker. Where the plate has seen -most light, corresponding to the deep shadows ofthe subject the gelatin may become so hardened as to prevent the absorption of practically any water by the calcium chlorid or if ysome small amount is absorbed the gelatin is too tough to be broken up. Thus the plate prints solid black at the deep shadows, as it should. Where the plate has seen no light whatever corresponding to the high lights of the subject, the gelatin is entirely soft, thus permitting therethrough and be Laatste Preparation of the press plate.

The press plate is preferably prepared from the key plate in an odset press as follows: Referring to lFig. 2, the key plate is placed on the bed 21 of the offset press and the press plate 22 is placed upon the bed 23.

The odset roller 2A which is provided with a toothed wheel 25 engaging with a rack 26 formed upon the bed is located between two plates and may take the odset from the key plate and print the same upon the press plate. Any suitable material may be used for the press plate, such as aluminum or Zinc or stone. When the press platehas received the impression, the same is examined carefully and parts which have not the desired strength are left open for correction and the rest of the plate is covered with gum arabic or gambouge for protection against the next impression. The key plate is then rolled up again with ink and an impression is again taken on the press plate. The part which has been leftopen is thus strengthened and when the gum arabic is washed od from the rest of the plate, the corrected part has the desired strength compared with the other parts of the plate. lf desired, Corrections may be made directly on the key plate with the aid of an air brush using steam instead of air. The portions to be weakened or reduced are subjected to the current of steam, the gelatin absorbing more moisture and thus subsequently taking less ink. Also if it is desired to strengthen or increase any portion may be subjectedto the current of steam from the air brush and thus the part not so. subjected will be relatively stronger or increased. This strengthening may also becaccomplished byl subjecting the particular part to be strengthened to a current of air from the air brush containing some suitable hardening agent which acts upon the gelatin. lf desired, the usual transfer paper method which has heretofore been employed to transfer the impression from the key stone to the press stone can be entirely eliminated and the impressions of the key stone may be multiplied upon the press stone by shifting vthe former upon the bed of the press. ln

this method of manipulation, assurance may be had that thevarious impressions upon the press plate are of equal strength, as the proof may be kept at hand with which the impressions are compared. Tf an impression is too light, another odset may be taken of the plate, the rest of the plate from the key plate and printed over the previous impression.

E citing of the press plate.

After the impression is taken upon the press plate, the same may be etched in some suitable manner:

ln the preparation of the key plate, l :have 4described the sensitizer as being applied to the plate in the form of a solution together with the printing medium. ln

some cases, however, may with advantageV ,apply the sensitizer 1n the form of a dust upon the printing medium which is otherwise prepared as above described. ln such case, the grain produced upon the printing plate is in the form of flakes which are smaller and farther apart at the lighter tones and darker and closer together at the darker tones. This variation in thel density of the grain is produced photographically as above described. Also if desired, the sensitizer may be applied separately in the form of a liquid'bath in which the plate is immersed after being coated with the other substance above described. This separate application of the sensitizer is especially ad- )vantageous-When' it is desired to keep a number of the coated plates in stock. The plates can thus be kept for a long time without any deterioration and when they are desired for use, the sensitizer may be applied.

Although l have described my improved process in connection with lithography, -it will be readily understood that the plate with the novel grain may be used with ad-y vantage also `inr relief and intaglio printing; in certain of the claims, T refer, therefore, to the key plate as the printing plate which may be used outside of the lithographie art.

lit will thus be seen that l have produced dll lill@ duces photographically every slightest grad-l uation .in tone of the original. The record upon this plate is a permanent one, and the ink may be entirely washed away without 'inJuring the printing quality of the plate. The various tones are reproduced through a grain which consists of interwoven sinuous lines or flakes which are lighter and more open at the lighter portions of the picture and heavier and closer together at the darker portions. These relative values of the grain are produced photographically to the finest detail and thus all the very finest graduations in tone are preserved. This makes it possible to obtain true color values with much smaller number of plates than has hitherto been possible. l havefound in many cases that three colors, as red, yellow and blue, are sufficient to reproduce all the tints of the original.

My improved processpractically elimi- *i nates hand work of an artist in the preparation of the lithographie key plate and press plate. All of the corrections necessary may, if desired, be, made directly upon the key plate, by closing or opening the grain at the desired point, by the use of a steam or air brush. The use of transfers maybe eliminated by using the off-set press to print through the offset roller from the key plate upon the press plate. The latter is etched in a novel manner calculated to prevent` injury to the finest detail work.

Although I have described my process in great detail, I desire it to be understood that I do not consider myself limited to these details, as numerous modifications Within the spirit of the invention will suggest themselves to those skilled in the art and portions of the improvements may with various degrees of advantage be used without the others.

Having thus described my invention I claim as new and desire to obtain by Letters Patent of the United States: f n

1. A process of preparing a lithographlc plate consisting in coating a plate with a gelatinous organic substance, a sensitizing agent capable after exposure to light o f rendering such organic substance insoluble 11i water and an agent which expands upon absorption of moisture and which will not 1nfterfere with the sensitiveness of the plate;

exposing the plate, washing 'the sameto remove the unexposed portionof the sensitizing agentl and then improving the printmg quality of the plate by coating the same with a solution of glycerin and sodium .chlorid and allowing the same to soak and then heating the same 'to a temperature'considerably below the boiling point.

2. A process of prepa-ring a lithographie plate consisting in coating a. plate with gelatin, a bichromate and calcium chlorid; exposing the plate, washing the same to remove the unexposed. portion of thesensitlzlng agent and then improving the printing quality of the plate by coating the 'same with a solution of glycerin and sodium chlorid, and allowing the same to soak and then heating lthe same to a emperature considerably below the boiling point.

3. A process of preparing a lithographie plate consisting in coating a plate with a gelatinous organic substance, a. sensitizing agent capable after exposure to light of rendering such organic substance insoluble in water and an agent which expands upon absorption of moisture and which will not interfere4 with the sensitiveness of the plate,-

heating the coated plate for a. definite period of time corresponding to the grain desired, exposing the plate, washing the same to remove the unexposed portion of the sensitizing agent and then improving the printing quality of the plate by coating the same plate consisting in with a solution of glycerin and sodium chlorid and allowing the same to soak and then heating the same to a temperature considerably below the boiling point.

4. A process of preparing a lithographie f plate consisting in coating a plate with gelatin, a bichromate, and an agent which expands upon absorption of moisture and which will not interfere with the sensitiveness of the plate, heating the coated plate for a definite period` of tlme corresponding to the grain desired; exposing the plate, washing the same to remove the unexposed portion of the sensitizing agent and then improving the printing quality of the plate by coating the same with a solution of glycerin and sodium chlorid and allowing the same to soak and then heating the same to a temperature considerably below the boiling point.

5. A process ofv preparing a lithographic plate consisting in coating a plate with gelatin, a bichromate and calcium chlorid, heating the coated plate for a definite period of time corresponding to the grain desired; exposing the plate, washing rthe same to remove the unexposed Aportion of the sensitizing agent and then improving the printing quality of the same by coating the same with a solution of glycerin and sodium chlorid and allowing the same 'to soak and then heating the same to a temperature considerably below the boiling point.

6. A process of preparing a lithographic plate consisting in coating a plate with a su'bstratum of sodium silicate dissolved in a solution containing albumen, then adding a coating consisting of a gelatinous organic substance, a sensitizing agent capable after exposure to light of rendering such organic substance insoluble in water and an agent which expands upon absorption of moisture and which will not interfere with the sensitiveness of the plate; exposing the plate, washing the same to remove the unexposed portion of the sensitizing agent and then improving the printing quality of the same by coating the same with a solution of glycerin and sodium chlorid and allowing the same to soak and then heating the same to a temperature considerably below the boiling point. v

7. A process of preparing a lithographie coating a plate with a substratuln of sodium silicate dissolved in a solution containing albumen, then adding a coating consisting of gelatin, a. bichromate, and an agent which expands upon absorption of moisture and which will not interfere with the sensitiveness of the plate; exposing the plate, washing the same to remove the unexposed portion of the sensitizing agent and then improving the printing quality of the same by coating the same with a solution of glycerin and sodium chloincasso p rid and allowing the same to soak, and then heating the same' to a temperature considerably below the boiling point. v

8. A process ot preparing a lithographie platte consisting in coating a plate with gelatin, a exposing the plate, washing the same to remove the Vunexposed portion of the sensitizing agent and then improving the printing quality of the same by coating the same with a solution consisting oit one part glycerin in a delinite period of time plate, improving same by coating one part. glycerin in one part*A 'ot water and one part of water and a .small amount ot sodium chlorid according to the humidity ot the air, allowing this coating to soak trom l5 to 30 minutes, removing the moisture and then drying the plate trom .two to ve minutes at a temperature of about 50 C.

9. A process ot preparing a lithographie plate .consisting in coating a plate with gelatin, abichromate, pand's upon absorption .of which will not interfere with the sensitiveness of the plate, heating the coated plate for corresponding to the grain desired then after exposing the the printing quality of the the same with a solution consisting ot a small amount of sodium chlorid according to the humidity ot the air, allowing this coating to soak from to thirty minutes, removing the moisture and then drying the plate from two to tive minutes at a temperature of about 50 C.

l0. A process ofpreparing a lithographie plate consisting in coating a plate with gelatin, a bichromate and calcium chlorid, heating the coated plate for a definite period of time corresponding to the grain desired; ex- "posingI the plate, washing the same to remove the unexposed portion of the sensitizing agent and then improving the printing quality of the same by coating the same with a solution consisting of one part glycerin in one part 'of water and a small amount oit sodium chlorid according to the humidity oi the air, allowing this coating to soak from hitech to thirty. minutes, removing the moisture and then drying the plate from two to ve minutes at a temperature ot about 50 C.

ll. A process ot preparing a lithographie plate consisting in coating a plate with gelatin, a`bichrornate and calcium chlorid, heating the coated plate tor a definite period oit time corresponding to the grain desired; then after exposin the plate improving the printing quality o the same by coating the same with a solution consisting of one part glycerin in one part of water and a small amount loit sodium chlorid according to the humidity ofthe air, allowing this coating to soak from teen to thirty minutes, removing the moisture and then drying the plate from .two to ve minutesl at a temperature oitv bichromate and calcium chlorid;l

and an agent which ex- Inoisture and?! applying warm moisture l2. A process of preparing a lithographie plate consisting incoating a vplate with a solution Aof thirty parts of gelatin to 300 parts of water to which is added 90 parts ot a solution of 1 part bichromate, -1 part ot calcium chlorid and 10 parts of water, heating a plate`so coated at a temperature between 50.and 60- C.; washing the same to remove the unexposed portion ot the sensitizing agent and/then improvmg the printing quality oit the same by coating the same with a solution consisting of one part glycerin in one part of water and a small amount of sodium chlorid according to the humidity of the air, allowing this coating to soak from fifteen to thirty minutes, removing the moisture and then drying the plate from two to tive minutes at a temperature oit' about 50 C.

13. A process ot preparing a lithographie plate consisting in coating a plate with a gelatinous organic substance, a sensiti'zing agent capable alter exposure to light ot' 1rendering such organic substancel insoluble 'coating acted upon by the light into a. grain,

the density of which corresponds to the degree 1n which the coating has been acted lupon by the light; then weakening or reducing the portions which are too strong by applying warm moisture thereon. p

14. A process of preparing a lithographie plate consisting in coating a plate with gelatin, a bichromate and calcium chlorid, then printing the image through a usual photographic negative directly upon the plate so coated and washing 0H' the unexposed portion of the bichromate and gelatin coating, the calcium chlorid serving to break up the coating acted upon by the light into a grain, the density of which corresponds to the degree in which the coating has been acted upon by the light; then weakening or reducing the portions which are too strong by thereon. p i

exposing the plate,

lll@

lia

15. A process ot preparing a lithographie plate consisting in coating a plate with a gelatinous organic substance, a sensitizing agent, capable after exposure to light ot rendering such organic substance insoluble in water and an agent which expands upon absorption of moisture and which will not interfere with the sensitiveness of the plate;

'then printing the image through a usual photographic negative directly upon the lplate so coated and washing ou' the unexposed yportion of the sensitizer and gelatin coating, said expanding agent serving to break up the coating acted upon by the light into a grain, the density of which corresponds to the degree in which the coating has been acted upon by the light; then reducing portions of the plate which are too strong by spraying steam thereon.

16. A process of preparing a lithographie plate consisting in coating a plate with a gelatinous organic substancefh sensitizing agentcapable after exposure to light of rendering suchv organic substance insoluble in Water and an agent which expands upon absorption of moisture and which Will not interfere with the sensitiveness of the plate; then printing the image through a. usual photographic negative directly upon the plate so coated and Washing off the unexposed portion of the sensitizer and gelatin coating, said expanding agent serving to break up the coating acted upon by the light into a grain, the density of Which corresponds to the degree in which the coating has 'been acted upon by the light; then strengthening the portions which are too Weak by a blast of air through an air brush with an agent Which serves to harden the photographic grain so as to take relatively more ink.

17. A process of preparing a lithographie plate consisting in coating a plate with gelatin, 'a bichromate, and an agent which expands upon absorption of moisture and -Which will not interfere With the sensitiveness of the plate; then printing the image through a usual photographic negative directly upon the plate so coated and Washing ofi' the unexposed portion of the bichromate and gelatin coating, said expanding agent serving to break up the coating acted upon the plate, then by the light into a grain, the density of which corresponds to the degree in which the coating has been acted upon by the light; then strengthening the portions which are too Weak by a blast of air through an air brush with an agent which serves to harden the photographic grain so as to take relatively more ink.

18. The process of preparing a printing plate consisting in coating the plate with a printing medium composed of an organic gelatinous substance and a substance capable after exposure to light of rendering such organic substance insoluble in Water, heating photographically printing the subject thereon; then washing the plate to remove the unexposed sensitized portions thereon and soaking the same in a solution containing a suitable hygroscopic agent.

1 9. The process of preparing a printing plate consisting in coating the plate with a printing medium composed of an organic gelatinous substance and a substance capable after exposure to light of rendering such organic substance insolublerin Water, heating the plate; then photographically printing the subject thereon, then Washing the plate to remove the unexposed sensitized portions thereon, soaking the same in a solution containing a suitable hygroscopic agent, then` further heating the plate.

Signed at NeT York in the county of New York and State of New York this 20th day of November, A. D. 1913.

LEO FREUDER.`