US1656235A - Process for reducing photographic silver image layers - Google Patents

Process for reducing photographic silver image layers Download PDF

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Publication number
US1656235A
US1656235A US10728826A US1656235A US 1656235 A US1656235 A US 1656235A US 10728826 A US10728826 A US 10728826A US 1656235 A US1656235 A US 1656235A
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Prior art keywords
process
image layers
reducing
photographic silver
silver image
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Plagwitz Paul
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Firm E Taeschner Chemisch Phar
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    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03CPHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C5/00Photographic processes or agents therefor; Regeneration of such processing agents
    • G03C5/26Processes using silver-salt-containing photosensitive materials or agents therefor
    • G03C5/40Chemically transforming developed images
    • G03C5/42Reducing; Intensifying

Description

Patented Jan. 1-7, 1928.

UNITED STATES PATENT OFFICE.

PAUL PLAGWITZ. OF BERLIN'STEGLITZ. GERMANY ASSIGNOR THE FIRM: E. 13;!!- SCHNEB, CHEMISCH-PHABMAZEUTISCHE FABRIK, OF BERLIN, GEBKANY.

PROCESS FOR REDUCING PHOTOGRAPHIC SILVER/IMAGE LAYERS.

No Drawing.

A number of methods have already been suggested for reducing negatives, films or positives. All these reducers, however, have the common fault,'that they affect the line half tones too strongly or entirely destroy the same. Another reducer has been suggested, which does not attack the fine half tones It is however rarely used, as its treacherous character greatly endangers the object to be treated and frequently com pletely destroys the same.

The new reducer consists in a preliminary hath containing in one litre of water:

1,6 gs. potassium ferricyanide.

3,3 gs. potassium bichromate and 1,5 gs. sugar.

The object to be reduced is immersed in this bath for about 3 to 5 minutes, is then quickly rinsed in water and is. thereupon immersed in a solution of 1 liter of water, 100 gs. sodium thiosulphate and coins. Ni sulphuric acid solution.

. The reducing process is eflected quickly in this bath, butstill slowly enough for the process to be carefully observed and to be interrupted immediate y the desired afieet is obtained. All that is then necessary is to wash the negative or positive thoroughly. .10 With this method it is possible to reduce even the hardest or densest negative or to lighten a positive which has been too dirkly 'printed or developed, without the fine .ones

being also reduced. With this method of at! treatment a very good gradation may be ob tained.

It has been found, when potassium.bichromate or some other alkali metal chromate or bichromate is present in. the reducing solua0 tion, gelatine 1n the vicinity of the silver appears to be tanned and made immune to t eaction of a reducer. It has also. been observed, that the presence of sugar has a favourable efiect on the results. The suhstances are, rubbed down with sugar inthe required proportlons so as to be intimately mired therewith and the powdered mixture 1925. Serial No. 107,288.

is dissolved in water so as to obtain the required concentration. 1

Example I.

A negative which has been made too hard by developing is immersed in a preliminary bath containing in one litre of water:

1,6 gs. potassium ferricyanide,

3,3 gs. potassium bichromate,

1,5 gs. sugar.

- After 3 to 5 minutes the negative isremoved, is rinsed in pure water and is immersed in a 10 to 20% acid sodium thios ulphate bath, until the visible reducing process has reached the desired degree. The negative is thereupon well washed in the usual manner. After this washing the process can be repeated, if desired.

Example II. I V

A silver bromide negative or positive which has beenunder or over-developed is immersed in a preliminary bath containing in one litre of water:

1,3 gs. potassium ferricyanide,

3,5 gs. potassium bichromate,

1,3 gs. sugar. V

After about 3 minutes the negative or positive is quickly rinsed and immersed in an ordinar 20% acid fixing bath. When the desire effect has been obtained, the visible reducing process is interrupted by rinsing with pure water, and the negative or positive is thoroughly washed in the usual manner. I i

The inventor has discovered quite generally that the best results may :be obtained when potassium ferrieyanide and sugar are used as the reducing medium and at the same time the lighter portions are made immune to the action of the reducer by treating the photographic image layers with chromates or bichromates of the A alkali metals. He therefore does not limit himself to the substances mentioned, but wishes to include all other means having an equivalent action.v

What I claim is 1. A process for reducing photographic silver image layers, consisting in treating the said layers in a preliminary bath with chromates of the alkali metals and at the same time with potassium ferri cyanide and in thereupon treating them wlth an acid sodium thiosulphate bath as set forth.

'2. A process for reducing photographic silver image layers, consisting in treating the said layers in a preliminary bath with bichromates of the alkali metals and at the same time with potassium ferri-cyanide and in thereupon treating them with an acid sodium thiosulphate bath as set forth.

3. A process for reducing photographic silver image layers, consisting in treating the said layer: in a preliminary bath with chromates of the alkali metals and at the same time with potassium ferricyanide and sugar, and in thereupon treatin them with an acid sodium thiosulphate ath as set forth.

4. A process for reducing photographic silver image layers, consisting in treating the said layers in a preliminary bath with bichi'omates of the alkali metals and at the same time with potassium forri-cyanide and sugar, and in thereupon treating them with an acid sodium thiosulphate bath as set forth.

In testimony whereof I have signed my name to this specification. a

- PAUL PLAGWITZ.

US1656235A 1926-05-06 1926-05-06 Process for reducing photographic silver image layers Expired - Lifetime US1656235A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US1656235A US1656235A (en) 1926-05-06 1926-05-06 Process for reducing photographic silver image layers
GB1431326A GB260892A (en) 1926-06-07 1926-06-07 Improved method of and means for reducing the intensity of photographic silver images

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US1656235A US1656235A (en) 1926-05-06 1926-05-06 Process for reducing photographic silver image layers

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US1656235A true US1656235A (en) 1928-01-17

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US1656235A Expired - Lifetime US1656235A (en) 1926-05-06 1926-05-06 Process for reducing photographic silver image layers

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US (1) US1656235A (en)
FR (1) FR614866A (en)
GB (1) GB260892A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2943935A (en) * 1957-05-15 1960-07-05 Gen Aniline & Film Corp Stabilization of photographic bleach powders containing an alkali metal ferricyanide

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2943935A (en) * 1957-05-15 1960-07-05 Gen Aniline & Film Corp Stabilization of photographic bleach powders containing an alkali metal ferricyanide

Also Published As

Publication number Publication date Type
GB260892A (en) 1926-11-11 application
FR614866A (en) 1926-12-24 grant

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