US1044793A - Process for making printing-plates. - Google Patents

Description

UNITED STATES PATENT curios.

ottnis'ror'nnn WILLIAM LUTTERMAN, or Noawoon, OHIO, ASSIGNOR TO u. s. LITHU- GRAPH COMPANY, OF NORWOOD,

No Drawing.

esses for Making Printing-Plates, of which.

the following is a. specification.

invention relates to a process of formmg or preparing printing plates or surfaces primarily for lithographic reproduction by a series of photographic steps.

The primary. object of my invention is to form a printing surface by photographically producing a half-tonepaper.enlargement 1n the form of a negative, which, by direct contact with a sensitized printing plate on exposure results in a reproduction of the original subject, with a preservation of the original artistic effects. The time, labor and cost in the preparation of a printing plate are reduced to a minimum. The artistic value of the product is enhanced and the natural and artistic tone values of the original preserved as well as thedelicate refinements-,which to a large degree are lost under the well-known methods of preparing the I subject upon printing plates.

-, in the half-tone positive.

The method employed consists in first producing a negative of the subject upon a glass plate and preferably by using a color filter if necessary to aid in separating the colors, with the exposure and development of the plate or negative to produce a proper gradation. r

, As a second step in the process, I-produce a half-tone positive by the use of a relatively fine screen placed a suitable distance in rear of the lens andbefore the sensitized plate,

with the negative placed before the lens, and a light reflected preferablyup'on a White sheet of vpaper placed before the negative A small diaphragm is -used in the" lens throughout the entire exposure. a screen positive from the negative made as heretofor describedit is possible to maintain distinct individuality of all of the dots proper gradationand all the tones are'per fectly rendered and in true reproduction of thenega'tive, the smallest white dot being in the dark portionswhich are the high lights in the ori inal and the smallest black dot being in t e light portions which are the Specification of Letters Patent. Application filed February 5, 1912.

the important aim in the In making- By this, step the.

OHIO, A CORPORATION OF JERSEY. PROCESS FOR MAKING PRINTING-PLATES.

Patented Nov. 19., 1912 r al No. 675,549.

shadows in the original, all the dots being perceptibly maintained. In this half-tone positive the dark portions of the first negative, are those portions which are light in the original and in consequence will be light in the positive, and the same condition exists with the dark portions, 6. 6, dark in the original, light in the negative and dark in I the positive. s

In fact, a half-tone positive is produced, a refinement maintainedand owing to the density of the negative the dots are not diminished nor overlapped but are merely defined through the actinism of the reflected rays penetrating the negative, maintaining the same relative uniform gradation oft-he negative. Y As a third step to the process, the positive half-tone obtained in the second step is projected upon a paper coatedwitha highly sensitive emulsion and which projection can beas an enlargement of the half-tone positive or a size desired for the lithographic reproduction. The enlargement, however, is use of this process,

enabling the following steps to be conveniently and practically carried on in making large-sized printing plates. At this step the high lights are characterized by the absence of the intensified or pronounced dot individuality, through a combination of difiusion of the reflected rays around the light dots in the half-tone positive by the side action of the large area of light surrounding the dot in the highlights,

and as the li ht dots are the smallest and faintest their e ectiveness is perceptibly lost in this step. This third step of taking an enlarged negative directly on 'paper from the glass half-tone positive is important and its significance should be understood with relation to the previous steps and the characteristics which it imparts to the finished product or printing plate. Assume, for illustration, original'suhject is a man in a dark suit of clothes with a, linen collar, the collar, of course, willibe the, lightestvportion, or, in other Words, represent'the high lights in photographic nomenclature. In the negative first taken, the collanwill be black, in the glass half-tone positive, second taken, the collar will again-be white,-and the mesh of the screen. will, appear as small black dots or the conventional'half-tone efi'ect, and in that the glass I paper, the collar will again appear as black,

. more pronounced by a prolonged exposure when making the half-tone but the dots will have been substantially eliminated, because in the enlarging, the dot: on the collar portion of the glass positive.

are surrounded b a white field and the rays projecting there rom in enlarging are diverged so that they comingle and become difi'used upon the exposed paper, the collar again becoming black on this paper negative.

and characterized by an absence or marked. reduction of the dots as compared to the half-tone positive, in so far as the collar portion is concerned.

Thus in the fourth step, which consists in. forming a positive half-tone on'the printing surface by direct contact and printing from the paper negative half-tone, the collar will again be white and notably free from the half-tone dots, while the darker portions of the image will be defined by the half-toning efiect, constituting raised surfaces which will impart ink to the lithograph, the collar portion bein relatively low owing to the relative a sence and density of the raised dots, so that no ink wlll be imparted to the lithograph and the collar will be white thereon; The other more or less shaded portions of the surface will be reproduced onthe lithograph in their relative gradations, mg lithograph printed from the plate will be a truereproduetion of the subject with the artistic effects and relative light and shade eifects preserved intact.

If the dot is required in the high lights for more satisfactorily printing some colors, such as for instance, bufiand gray, the dot 1n the high lights 'is made larger or positive, or by makmgthe first glass negatlve thinner or developing the samelighter. Thus if the dot 1n 'the half-tone positive in the hi h lights is of larger area, it will considerab y retard the dlfiusion of the light rays toward the medial pointof the dot, thereby roducmga more pronounced dot in the go lights -m the half-tone. paper enlargement and 1f not develo ed out will have their resultmg effect in t e transfer upon the printmg plate. p

In fact, with my process by exposure and development 1t 1s possible at the 'last stage in the enlar ement upon the developing aper to pro uce a negative, in which the I individuality of the artist is maintained and 'tained, more-delicate and harmoifious than under the'well known methods of producing lithographic stone printing plates.

so that the result and developing said negative;

negative upon a Fourth step: After the half-tone paper negative has been properly finished, it is placed in direct contact with a metal plate or stone which has been previously sensitlzed with a bichromatizerl colloid, the paper is held or clamped smoothly over the surface and so maintained and exposed to the light, obtaining a print upon the sensitive prmting plate. After a proper exposure, the plate is developed and etched, either fiat or in relief, to suit the particular purpose or press-work. This preparation of the printing plate is carried on under the wellknown methods common in the art.

In making a plate print, the density of the dot can be readily varied in making a darker or lighter print entirely, making it possible to make corrections in color not taken care of by proper color separation in the first step of the procby more or less ex- I posure. The shadow dot may be eliminated ess in making printing plates for colorreproduction.

Having described my invention, I claim 2-- 1. The herein described .process for forming a lithographersplate, which consists, in first taking a negativedphotograph of the subject upon a sensitize developing said plate; second, in takmg. a half-tone positive photograph of said negative upon a sensitized glass surface, using a screen and diaphragm arranged to form dotsthroughout all portions of the positive, and developing said positive; third, taking an enlarged negative photograph of sea half-tone positive upona sensitized surface suitable for photographically printing therefrom, effectually in the high lights during this third step,

fourth, phoglass plate and -hminating the dots tographically printing from said enlarged plate,

using 'arel-atively small diaphragm and fine form dots throughout creating dots in the'lower lights screen so placed as to all portions of the positive,

the high lights as well as in sensitized lithographers of the positive, and developing said 'pos1- tive; third, taking an enlarged negatiye photograph of said half-tone positive upon a' sensitized surf-ace suitable for photographic printing therefrom and effectually reducing thedots in thehigh lights during the third step so as to produce substantially pure high lights in the resultant enlarged negative, developing said negative; fourth, photographically printing directly from 1,044,793 B seid enlarged megat-ive upon ,a sensitized In testimony whereof,q I ha e herennto hthographers plate and finally finishing set my hand.

said plate, to produce a printmg surface characterized by an absence of dots in the CHRISTOPHER WILLIAM LUTTERMAN;

5 high lights and the resenc'e of dots in the Witnesses lower llghts, relative y graded to reproduce OLIVER B. KAISEJR, the true tone values of. the-original subject; CLARENCE B. FOSTER.