US1600797A - Asfllokob to babjkicav kodak ook - Google Patents

Description

Patented Sept. 21, 1926.

UNITED STATES PATENT OFFICE.

:omt o. warm, or momma, naw roux, Assxenoa ro am mu: comrm, or nocnnsran, new roan, a conroaarron or m roan.

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80 Drawing.

This invention relates to an improved photographic reversal process and more particularly to a step therein for reventmg reversal. The improved step W1 be described 5 as inco rated in the process covered by my Patent 0. 1,480,703, granted July 3, 1923. The principal steps of that process were successively, exposure, development, removal or bleaching of the silver image, clearing, I controlled re-e re, redevelopment and a final fixing. If a tendenc to re-reversal was found by test to take p ace at the second development, there was introduced a step to overcome this tendency, this step comprising 1 an alkali bath prior to IQ-GXPOSUI'Q and redevelopment.

I have since discovered cases of re-reverse] that were not satisfactoril overcome by this treatment and I have furt ier discov- 0 end that these occurred when a fresh bleaching or reversing both, such as is described in step 4 of the patent, was used for the first time; but that the tendenc disappeared after the bath had been use a short time. 25 Further research disclosed the fact that this tendenc is not found when there is present in the leachin or reversigfi bath a small amount of a uble silver t. im roved step consists in the condil0 tionlng c this reversal or bleaching bath by the purposeful addition thereto of such a. solution. This conditicni ma; be accomplished in various ways, 0 which the folowing is an instance. To one liter of a bath I made in accordance with the formula given in step 4 of said patent may be adde 2%; cc. of a'10% solution of silver nitrate. A second method of introducing the soluble Silver salt, useful when a continuous machine 40 such as is described in my application Serial No. 618,846, filed February 3, 1928, is used is to run a strip of waste film through the machine includin thebleaching bath 1'10! o its use in regufiar work. This won (1 be I done by fogging such a strip and using it as a leader for the regular film, then drawing it throu h the developing and bleaching baths. 'fiie action of t e b caching bath on the developed silver of the waste stri would introduce silver salt into the bat The length of such a strip would have to be ascertained by ex rilnent under the conditions present in e actual apparatus. A third Application fled January s1, ms. and In. em.

way of attaining the desired object is to add to a newly pre ared bath a qgantity of ii aid from a or exhausted leaching bat and this quantity; wouldnleo, of course, have to be determined b experiment and the actual condition content of the used hath. However, the first method mentioned gives a precise step available to those without experience.

Tlge re-revgreal rgenticnled ishusually a com ination o nega 've an 'vei and not a complete re-reversn f lt refit? appear most strongly when there was originally an under-ex are in the camera, Since in such cases t ere is little silver in the developed image and thebleaching bath is slow to acquire a silver salt from its action on this thin image. If thee incl developed image is very ense, the ten encyjo re-reverse disappears much more uickly because of the re d formation 0 the silver salt in the blee ing bath. II

This invention is of particular use in the reversal procem described in m atent in which the re-exposure is contro e -and in which all the sensitive silver salts are not usually redevelc because re-reversal cannot occur in t e usual reversal processes wherein all the sensitive silver salts are redevelo d.

e theory pnderlyin the cause and prevention of this type 0 re-reversal is obscure.

As stated in the patent, the preferred reversing bath is as ollows:

Potassium permanganate (4% so- As described in the patent, the bath contains about 1% of sulphhuric acid, and the silver salt formed in e bleaching o eration is silver sulfate. When silver nitrate is added to the bath it is transformed into silver sulfate. When silver salts less soluble than the sulfate, such as the halides, are added, the result is not obtained. It ap rs to be necessary to use a salt which w: l be transformed into the salt of the acid of the bleaching bath, in this case the sulfate.

The bath as used substantially contains silver salt to produce a saturated solution of silver sulfate in the bath. The solubility of the sulfate increases with the acidity of the bath and as the acidity of the bath may vary, as was stated in the patent, the amount of sulfate may correspondingly vary.

In each of the various methods mentioned above it will be seen that this salt is incorpo-' rated in the bath .when it is initially used for its intended purpose.

Having thus described my invention what I claim is new and desire to secure by Letters Patent is:

1. The method of conditioning an acid bath for use in a photographic reversal procase for bleachingra silver image preparatory to Ive-development that comprises the incorration therein of a silver salt correspond-v mg to the acid of the bath.

2. The method of conditioning a bath containing sulfuric acid for use in a' hatephlc reversal process for bleaching a silver image preparatory to re-development that comprises t e incorporation therein of silver sulfate.

3. The method of conditionin a bath comprising a permanganate an sulfuric acid for use as a bleaching bath for a silver image preparatory to re-development thereof with a silver ima e to an acid bleaching bath and to a rediaveloping bath, the improved step that comprises using for bleachmg a bath that has initially present a silver as t of the acid of the bath. 5. In a photographic reversal process comprising successive y submitting a carrier with a silver image to a bleaching bath containing sulfuric acid and then to a redeveloping bath, the improved step that comprises using for bleaching a bath that has silver sulfate initially present.

6. In a photographic reversal process comprising suocessive y submitting a carrier with a silver image to a bleachin bath containin a permanganate and an furic acid and t en to a redeveloping bath, the improved step that comprises usin for bleachmg a bath that has silver sul ate initially present.

Signed at Rochester, New York, this 29th day of January 1925.

I JOHN G. CAPSTAFF.

silver sulfate in the bath. The solubility of the sulfate increases with the acidity of the bath and as the acidity of the bath may vary, as was stated in the patent, the amount of sulfate may correspondingly vary.

In each of the various methods mentioned above it will be seen that this salt is incorporated in the bath when it is initially used for its intended purpose.

Having thus described my invention What I claim is new and desire to secure by Let ters Patent is:

1. The method of conditioning an acid bath for use in a photographic reversal process for bleaching a silver image preparatory to re-development that comprises the incorporation therein of a silver salt corresponding to the acid of the bath.

2. The method of conditioning a bath containing sulfuric acid for use in a photographic reversal process for bleaching a silver image preparatory to re-development that comprises the incorporation therein of silver sulfate.

3. The method of conditioning a bath comprising a permanganate and sulfuric acid for use as a bleaching bath for a silver image preparatory to re-development thereof that comprises the incorporation therein of silver sulfate.

4. In a photographic reversal process comprising successively submitting a carrier with a silver image to an acid bleaching bath and to a redeveloping bath, the imroved step that comprises using for bleach mg a bath that has initially present a silver salt of the acid of the bath.

5. In a photogra hic reversal process comprising successive y submitting a carrier with a silver image to a bleaching bath containing sulfuric acid and then to a redeveloping bath, the improved step that comprises JOHN G. CAPSTAFF.

New York, this 29th Certificate of Correction. It is hereby certified that in Letters Patent No. 1,600,797, granted September 21.

1.926, upon the application of John G.

(lapstaii, of Rochester, New York, for an improvement in Reversal Processes. an error appears in the printed specification requiring correctimi as follows: Page therein that the same may con int ;n in

[swan] l. read rsermwmsul; and that the said h tters the record her, A. l). 1926.

lines 3 and 4, for the word reversal" Fatcnt should be read with this correction oi? the case in the Patent Office.

\Vltl. A. h'liNNAN, Actny Lmrzmsaiii-mar of i afent-a.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1. 6fi0,797, granted September 21, 1926, upon the application of John G. (Tapsmfl, of hochester, New York, for an improvement in Reversal Processes, an error appears in the printed specification requiring COII'GC-UUD as foilnws: Page 1, lines 3 and 4, for the word reversal read res-reversal; and that the said Letters Patent should be remd with this correction therein that the same may conform to the record of the Case in the Patent Office.

Signed and sealed this 19th day of October, A. D. 1926.

[SEAL] WM. A. KINNAN,

Acting (iommissimer 0/ Pafents.