US1273797A - Tellurium toning-bath and process of toning photographic elements. - Google Patents

Description

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To all whom it may oncern e it known that I, Ennuxn R. liomiorn. of Rochester, county of Monroe, State of New York, have invented certain new and useful Improvements in Tellurium 'loning aths and Processes for Toning Photo graphic Elements; and I do hereby declare the following to be a full, clear, and exact description of the same.

y invention relates to photography and more particularly to toning baths and the process of toning photographic prints and as for its object the provision of a satisfactory and easily manipulated toning bath and a process for toning whereby a rich brown or sepia color effect may be obtained which is highly pleasing to the eye. To this and other ends, as will appear from the following disclosure, my invention resides in the combination of nuts and the steps of the process as set forth in the appended claims.

In the practice of my invention, I utilize a toning bath for transforming the ordinary lack and white tones of a silver image into a brown or sepia color efi'ect which comprises an acid solution containing a compound of tellurium and which furnishes a molecular compound or an ion in solution capable of reacting with silver to form an image which is insoluble in water or preferably insoluble in the toning bath.

solution of a telluriuin halid, preferably a chlorid of t'etravah-nt tellurium, in a hydrogen halid acid is found to be well suited for this purpose and to produce excellent sepia tones. While an excess of acid in the solution is preferred, there should be utilized sutiicicnt acid to oppose any tendency toward complete hydrolysis and mainsalt in solution to carry on the toning, reaction. A bath involving the halid of tellurium may be formed, for dissolving tellurium dioxid TeO in hydrochloric acid, an excess of the latter being present. The tetravalent tellurium salt, tellurium chlorid (Tech), is probably present in the bath and servesas the reagent which forms with ima e a compound that is substantially insolu le in the toning bath.

If other element, such as plate film or paper bearing a silver image whiehhas been developed, fixed and washed in the usual man- Speeification of Letters Patent. Application filed April 5, 1916.

an ordinary photographic print or tatl Patented July 23, 1918. Serial No. 89,017.

nor. is immersed in the telluriuin bntluthe photographic print or other element changes from its former approximately black or silver color to a sepia tone, probably due to the formation of a compound of silver and tellurium according to tion:

in which X represents the halogen or other ion that reacts with the silver to form the insoluble compound. Both the resultant pr ducts in the above reaction are insoluble in the bath, but the silver-tellurium compound due to its predominating furnishes the tone to the image, the other salt merely degrading the color eifect some what.

Since the bath should be free from injurious substances or those which tend to attack the gelatin or which have a tendency to dissolve the silver before it has had time to tone, or to dissolve the silvertelluriuin compound after the toning has taken place, I preferably utilize dilute hydrochloric acid as the solvent for the telluriuin compound. due to the slowness of reaction of the tellurium chlorid in hydrochloric acid on the silver image, I find it desirable that the bath contain an adagent to accelerate the velocity of the toning process. Also, it is found that after the toning has taken place and the print is being washed, the extreme dilution of the solution of the tellurium compound present in the pores of the gelatin tends to form a precipitate oi the oxid or hydrated oxid on the print, although acid has been used in the initial solution. This deposit, at first white in color, tends to be gradually reduced by the gelatin to form a black deposit over the entire print. To overcome the formation of an undesirable precipitant and to accelerate the reaction velocity, I add to the tellurinm halid bath a halid of an alkali metal, preferably a bromid. Advantageous results are obtained by using sodium chlorid and potassium bromid, By utilizin t, these salts it is possible to dilute the toning bath indefinitely or to wash the print completely without danger of precipi 'on of an undesirable tellurium compound because of hydrolysis.

s a' specific example, the following ingredients and proportion measured in grams the following equaa mixture of and cubic centimeters may be en'iployed for use with one well known brand of pliolographic silve emulsion paper, although. of course, they may be varied to accord with the character of any other kind of photographic element; that is to be sepia toned:

in. Tel) l'lCl (concentrated.) J in. NaUl. in. Kllr. ater to make 100 cc.

'hile the chemical structure of the compounds present in the tellurium bath and the exact nature of their reactions is immaterial, so far as the character and operation of my invent ion is concerned, there may possibly be present in the acid bath containinp, the alkali metal lialid salts, a double salt of the type Na. ,'lellr,,; however, the reaction may be represented as proceeding according to the following simple formula, tellurium clilorid being considered the reactive agent:

Tcul l lKlir-ttiAg:

Ae 'l'elAgBr+ thCl By using baths of the above spccilic natures. a sepia tone is obtained, no further chemical treatment oi the print being iieces sai'v. However, it is preferable to add anotlii-r step to the process to obtain a deeper and richer ctl'ect and to regain the density of the original print, which was slightly reduced by the bleaching action of tlie tellurium bath. l, accordingly, wash the print, preferably in running, water, for a sutlicient time to remove the acid solution and then treat. the image with a Nafi solution, pref erably a two per cent. solution of sodium sullid crystals. The result of this step is probably to transform the white or light colored silver broiiiid or silver clilorid, which otherwise would tend to change to a pliotobroniid or photochlorid upon exposure ol the photographic element; to light, into the dark colored and more permanent silver sulfid, the print being given thereby substantially the same density as was originally present.

The operation of my process is simple. An ordinary silver print, for example, after the usual developing, lining and washing op erations, is immersed in a tray containing my tellurium toning bath or otherwise treated therewith for about two minutes or until the visible change in the print is complete, preferably while the tray is rocked or the solution otherwise stirred. It is inadvisable to prolong tlie treatment ol the print with the tellurium solution after a. satisfactory result is obtained, as the color values ma be disadvaiitageousl alli-cteil thereby. The print; may then be washed and dried, or, if the sodium sullid treatment is desired, it; is

'ver tellurium. and

washed preferably until ll'it" acid has been substantially eliminated and then treated with a two per cent. aqueous solution of sodium suliid to darken and intensify the print. When the color change has taken place, the print is washed and dried in the usual manner to complete the process.

Ilaviing described my invention, I claim:

1. A photographic toning bath for silver images comprising a tellurium compound in an acid solution, said bath being capable of converting the silver image into one which is insoluble therein.

2. 'A photographic toning solution for silver images comprising a compound of tellurium and an acid, said solution being capablc of forming a compound containing sila silver salt which are insoluble in said bath.

A photographic toning solution for silver images containing a compound o l' tetravalent tellurium and an acid, said solution comprising a substance which is capable of forming a compound containing silver, tellu rium, and a silver salt that are insoluble in said solution.

4. A photographic toning bath for silver images comprising a tellurium compound,

water, and an acid which will prevent precipitation ot' a tellurium compound and will not injuriously attack the silver image.

5. A photographic sepia toning ath comprising a tellurium salt in a solution cont-aining a hydrogen lialid acid.

(3. A photog; aphic sepia toning bath comprising a tellurium clilorid in a solution acidilied only with hydrochloric acid.

7. A photographic toning bath comprising a solution containing a tellurium lialid and an accelerating agent.

8. A photographic toning bath couiprising a solution of a tellurium salt and an agent capable of retarding hydrolysis and precipitation of a tellurium compound upon dilution with water.

9. A photographic sepia toning bath cor prising a tellurium chlorid in a soluiii...

containing hydrochloric acid in excess and a lialid salt.

10. photographic sepia toning bath omprising a tellurium compound in a solution containing hydrochloric ac d in excess, sodium chlorid and potassium broinid.

11. A j photographic toning bath comprising tellurium chlorid, hydrochloric acid in excess, sodium chlorid and potassium bro-. mid.

12. The process of sepia toning a photographic silver image comprising the step of treating the silver image with an acid solution containing a tellurium salt.

13. The process of toning a photographic silver image comprisin the step or changing the color of the silver image by ti ating it ll a. solution of tellurium cliloricl dissolved in an excess of hydrochloric acid and producing a silver compound that is insoluble in Water.

14. The process of toning a photographic silver image comprising the steps of. treating said image with a solution of a tellnrium salt to produce a given tone; and mo lifying said tone by treatment with a sullid solution.

15. The process of toning a photographic silver image comprising the steps of treating the image with an acid solution of a tellurium salt to produce a given sepia tone and treating with sodium sulfid to modify said tone.

16. The process of sepia toning a photographic silver image comprising the steps A of bleaching and sepia toning the silver image with a solution containing a tellurium halid and intensifying and modifyii g the tone of the image by treating with a sodium sulfid solution.

17. The process of toning a photo raphic silver image comprising the steps 0. treating said image with an aqueous solution of tellurium ClllOX'lll, hydrochloric acid, sodium chlorid and iotassium bromid and thereby bleaching am toning the image, and intensifying and modifying the tone of the image by means of an aqueous sodium sulfid solution.

In witness whereof I affix my signature this 1st day of April, 1916 in the presence of two witnesses.

EDMUND R. BULLOCK.

Witnesses:

ALONZO S. MCDANIEL, G. C. COOKE.