US1852115A - Process of preparing printing plates - Google Patents

Description

. 1 5, J. HAGGERTY ETAL ,852,115

rnocnss or PREPARING PRINTING PLATES Filed Dec'. 24, 1950 HFTER BEING JUBJ'fiC 7750 70 HIGH PEJFSSURE Zmnentora JOHN HR 66 E B T) and DA V/D JOHA/6 TON zmwu V Patented Apr, 1932 UNITED STATES; PATENT jOF FICE JoH HAGGERTY, or EAST oEANGE, NEW JERSEY, AND'DAVID .ronNsroN; or BALD- WIN, NEW YORK v PROCESS OF PREPARING PRINTING PLATES Application filed December 24, 1980. Serial No. 504,638.

This invention relates to improvements in printing plates and processes of preparing the same and it has for its object to provide an originalplate of such character that when a used as an original plate from which to produce electrotypes, nickeltypes, stereotypes,

lead molds or other printing plates, the latter will come from the mold with the proper makeready or tone characteristics embodied to in them; to provide a. process by which an original or master plate made as usual in other respects can be reformed by simple treatment readily within the range of such skill as is conveniently obtainable in the art so as to embody in itself the desiredcharacteristics requisite to impart to the final printing plates! made from this original plate self-contained makeready characteristics; to

provide a process or method ofv making and preparing printing plates which enables the makeready treatment of the original makeready plate to be susceptible of test from time to time to the end that the desired replates which is extremely economical in that the makeready is imparted to the original plate only and any desired number of electrotypes or other reproductions may be made 39 from such original, each having the same makerea-dy characteristics; to provide a method which greatly minimizes the chance of errorsin setting up the forms and securing the exact results desired; .to provide printing plates and the process of making the same which produces plates suitable for use on most, if not all,-of the modern print ing presses; to provideprinting plates of a character especially valuable and advanta- 40 geous for use in multicolor printing and particularly when such multicolor printing is done on multiform presses which impart the several color impressions to the sheets of paper as it passes through the press a single time and in general to produce .printlng the process wherein the back of the plate has been etched after being printed with a negative made from the front of the plate.

Figure 3 is an enlarged detail view of the finished plate after the printing face of the plate has been subjected to high pressure.

The process according to the present in-' vention is as follows a After the front or printing face of the plate has been printed on metal and in the usual photoengraving manner, we take the negative flat which has been already printed as above, lay on a glass table, letting the light shine through, painting in extreme highlights in silhouettes, vignettes etc. with opaque, which prevents lights shining through when printed onimetal therefore recording pure white without screen dots. We then make suitable register marks and drill a needle point hole through each register mark. The

various negatives on the fiat are then united as one so that they can be taken ofi the fiat. This we do by coating them with a rubber solution and then with a stripping coat of collodion which prevents the stripping coat from mixing with the screen coat. We coat the plate three times with stripping collodion, drying each coat before the next coat is applied. Three coats are necessary so that the film will be thick, firm and will not stretch. The negatives, now one film, are then soaked off with diluted acetic acid and stripped from the flat or plate glass. They are then reversed then coat the back of the plate with a cold enamel, place the reverse negative on the back of the plate in accurate position by means of the register marks which register with 2 etched in an etching machine,

parts that have been the holes through the plate. This gives a perfect register. We now print the back of the plate in the same manner as ordinary photoengraving is printed. The back of the plate now has the same subjects printedthereon in perfect register with the subjects on the front of the plate. We now spot the front of the plate to cover defects not covered with enamel. We then examine the back and highlights not already taken care of with the opaque painted in, and then rub off enamel with pointed pieces of charcoal, Scotch stone or a scraping tool. The plate can now be both sides at once, half minute front and half minute back, and reverse until tach side has had a minute or more according to the judgment of the photoengraver. The front of the plate is then finished in the usual manner. The images. are then .very clear, the back being just the same as the front. The back of the plate is then rubbedwith magnesia chalk and o aqued; charcoaled, Scotch stoned or scrape are lower than the rest of the plate which are covered with enameL- We now clean off the enamel from the back with lye, potash or other suitable chemical, leaving the pure copper of the back exposed. We then coat the entire front or printing face with shellacand paint in dark tones on the back with shellac or other acid resisting solution and give the late another etch in the etching machine.

however, to finish the printing face of the plate in the usual manner, then rub chalk of magnesia into ,the flat plate of many subjects, then photograph the flat plate with a camera equipped with scales which will produce a negative with the exact dimensions of the plate, the photograph being taken without a screen and exposing the negative until the highlight dots are dro ped out of the negative,

then coat the bac of the plate wit sensitized film which shows the register marks and register the negative with the holes bored until the highlight dots are droppe I We then register the negative with the holes Ve then rub. chalk on the back of the plate to more clearly see the depths of the etching and if necessary paint in the lighter through the register marks on the front of the plate and then print and etch as heretofore described, the front of the plate being protected by a coating of shellac. This method eliminates the coating of the negative, stripping it, turning it and saves much time and labor. When the'back of the plate is finished, the front of the plate is subjected to high pressure as'before described to impart makeready characteristics thereto.

In two, three or four color work we do not use original negatives because they do not show true separations until worked out by color etcher. After the color job has been O.K.ed and no further corrections are necessary, we rub chalk of magnesia into the plate showing the'screen dots up very distinctly. The plates are then photographed with a camera equipped with scales which will produce a negative with the'exact dimenslons of the proof, without a screen and exposing the ne ative out.

bored through the register marks on the front of the plate and then rint and etch "as heretofore described, the rout of the plate being protected with a coating of shellac.

After the original plates are treated as described, the original plate is then placed in a hydraulic press preferably with hard surface cardboard on the face of the plate and pressure applied to the extent necessary to lower the highlights and semi-solids to the required amount. Electrotypes, stereotypes, etc. can readily bemade from the original which will produce the m'akeready characteristics of the'original plate, eliminating the usual labor'of makeready resulting in great saving of labor and time. The average time consumed on an eighteen'page form is about one and a half hours per plate.

Having described our invention, we claim: 1. In a process for imparting makeready characteristics to metallic printing plates, the steps of photoengravin images on the front or printing face of'tlie plate, photographing the printing face of the plate, plac- 1ng the negative on the back of the plate in; register with the picture on the front of the plate, printing and etching the back of the plate and then subjecting the front of the plate to high pressure.

2. In a process for imparting makeready characteristics to metallic printing plates, the steps of photoengravin images on the front or printing face of the plate, photographing the printing faceof the plate without an screen, placing the negative on the .back 0 the plate in register with the picture on thefront of the plate, printing and etching the back of the plate and then subjecting the front of the plate to high pressure.

3. In a process for imparting'makeready characteristics to metallic printing plates,

the photograph being taken

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