US1472048A

US1472048A - Method of hardening of photographic films

Info

Publication number: US1472048A
Application number: US336920A
Authority: US
Inventors: Christensen Jens Herman
Original assignee: Individual
Current assignee: Individual
Priority date: 1918-11-20
Filing date: 1919-11-10
Publication date: 1923-10-30
Anticipated expiration: 1940-10-30
Also published as: DE334277C; FR506205A

Description

Patented at so, ?1923.

Parent oar-tea.-

JENS HERMAN CHRISTENSEN, F HOLTE, DENMARK.

METHOD OF HARDENING 0F PHOTOGRAPHIC FILMS.

We Drawing. Application filed November To all whom it may concern:

Be it known that T, J ENS HERMAN CHRIS- TENSEN, a subject of the King of Denmark, residing at Holte, Denmark, have invented 5 a new and useful Improvement in Methods of Hardening of Photographic Films; and

I do hereby declare the following to be a full, clear, and exact description of the same.

It is well known that" through development of an exposed photographic film, containing silver halide and gelatine, by certain developers, for instance such containing pyrogallol, pyrocatechin, hydrochinon, etc., a relief can be obtained which is due to the fact that the gelatine is hardened in such places in which the development has taken place. For most practical purposes this hardening, however, is too slight and very much inferior to the known hardening by exposure of chromate containing gelatine.

lit has now been proved that this hardening through development can be augmented in an exceedingly high degree so that it can be compared to the ohromate hardening and thus can substitute the same in photographic as well as in photomechanical processes, if such provisions are made that the gelatine during the development is preventedfrom attracting liquid and swelling to any important degree. This is obtained by adding to the developer a suitable very great quantity of such substance which will counteract the swelling of the gelatine, for instance alcohol or greater quantities of salts of poly-basic acids, for instance carbonates, silicates, etc. Such substances singly or in mixtures, are used as components of generally known developers, but in far smaller quantities. The desired effect, however, will onlyappea-r if the gelatine during the development remains solid and leathery and permits slow penetration by the developer solution. According to this invention these substances therefore are added in such large quantities that the said solid, leathery" consistency of the gelatine 'is preserved during the development. The followin is an example of the carryin out of the invention:

The exposed plate is developed ina dark room with a developer consisting of 7 5 parts of alcohol, parts of water, 2 parts of potassium carbonate, p of pyrocatechin, .or alcohol may be le out of the above named formula when in return the quan 10, 1919. Serial No. 336,920.

'The development should preferably last several minutes and can be retarded if desired for instance by adding potassium bromide or boric acid 7 A good composition of a developer for finely grained silver bromide plates is for instance the following 180 parts'of water, parts of potassium carbonate, 3 parts of potassium bromide, 1 part of pyrocatechin, 20 parts of alcohol.

When the development is finished, the plate is rinsed and may if wanted be fixed, and thereafter it behaves like a chromate hardened gelatine' plate, which is to say for instance. that the non-hardened part may be washed away with hot' water or be brought to absorb dye solutions so that the plate can be used as a printing plate.

Specially adapted for this treatment are the socalled silver-chloride-bromide plates which further have the advantage of being sensitive to light of difi'erent colors and easily controllable during the development as the sensitiveness is not very great.

Such silver chloride-bromide plates there fore are adapted for the production of printing plates forv three color prints.

The said printing plates may be flexible, the film being arranged on a carrier of celluloid or metal and they may have a suitable perforation in order to facilitate the registering during the exposure and printing.

Having thus fully described my invention .1 claim as new and desire to secure by Letters Patent:

1. The method of developing photographic plates or films to provide a picture of hardened gelatine which consists in treat- Q emmas graphic plates or films to provide a picture In testimony whereof I have aflixed my of haidened gelatine which consists in treatsignature in presence of two Witnesses.

ing t e exposed and undeveloped plate or v film with pyrocatechi'n and a mixture of TENS HERMAN CHRISTENSEN 5 alcohol and .a substance selected from the Witnesses:

group consisting of potassium carbonate CECIL V. ScHoN, and potassium bromide. VIGGO BLoM.