US750014A - Thomas bakee - Google Patents

Description

UNITED STATES Patented January 19, 1904.

PATENT OFFICE.-

THOMAS BAKER, OF MELBOURNE, VICTORIA, AUSTRALIA.

PROCESS OFPREPARIING QPHOTOGRAP'HIC PRINTS FOR TONING.

SPECIFICATION forming part of Letters Patent No, 750,014, dated January 19, 1904.

A li ati fil d November 21, 1902. Serial No. 132,329. (No specimens.)

To all whom it may concern.-

Be it known that I, THOMAS BAKER, a subject of the King of Great Britain, director of Baker and Rouse Proprietary, Limited, residing at No. 260 Collins street, Melbourne, in the State of Victoria and Commonwealth of Aus tralia, have invented certain new and useful Improvements in Processes of Preparing Photographic Prints for Toning, of which the following is a specification.

When toning is to be effected in the case of What are known as printing-out papers, it is necessary before placing the prints in the toning-bath to remove from them all the soluble silver salts which they contain unless the toning is to be effected in what is known as a combined bath, which, however, is not generally employed. The removal of the soluble silver salts has hitherto been carried out by washing the prints in many changes of water,

' which is both tedious and troublesome and in vert the soluble silver salt contained in it intoan insoluble silver salt or combination ormix- .ture of insoluble silver salts, and yet leave no injurious excess of soluble haloid or haloids in the film, and that the print may after such treatment be placed without Washing (or with only sufiicient washing to rinse away the superfluous solution of chlorid or other salts from the surface of the print) directly into the toning-bath, and that the toning will then go on'much in the same way as if the print had been washed.

I am aware that it has been customary to treat prints with a solution of a chlorid before toning; but it has always been done with a solution of such strength that an injurious excess of chlorid remained in the prints and the washing of the prints has been equally or even more necessary than if theyhad not been so treated. I have also found that the addition of an iodid or bromid to such a solution as I have mentioned above has a marked and beneficial influence upon the course of the toning and that the high lights of the prints so treated are far less liable to be affected injuriously in the toning-bath than if the iodid or bromid or even for some tones a combination of the two had not been employed.

The color of prints treated by iodid in solution previous to toning is less changed by the subsequent operation of fixing than if it had not been used, which also is decidedly advantageous.

The solution of the haloids, as mentioned above, may contain with advantage a substance or combination of substances which has or have the effect of hardening or tanning gelatin, such as alum of various kinds, salts of aluminium, tannic acid, formol. An excellent combination is as follows, and it is suitable for most makes of printing-out papers, though it may require adjustment to suit any particular brand. If there is a milky deposit upon the surface of the prints when they are placed in it, the solution is too weak, and if the toning operation is slowed by it it is too strong, either of which defects may be remedied by using a little more or less water in making up the solution: chlorid of sodium, one and one-fourth grains; sulfate of alumina, five grains; water, one fluid ounce; but I do not'confine myself to this exact formula. The prints are dipped into such a solution, allowed to remain in it until they become limp and lie flat, when they are withdrawn and either placed directly in the toning bath or rinsed with water to wash away the superfluous solution from the surface.

A suitable solution containing iodid is made by replacing portion (say. one-half) or the whole of the chlorid of sodium in the above formula with its chemical equivalent of iodid of potassium or other soluble iodid.

When a bromid is added, the proportion should not exceed one grain in forty ounces of the solution, as otherwise the toning would be renderedtoo slow.

If iodid alone is used, the toning is also somewhat slow; but bromid alone is too slow for practical purposes.

Having now particularly described and as- 5 certained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is The herein-described process of preparing photographic prints for toning, which con- 1 O sists in treating the prints with a solution consisting of chlorid of sodium, sulfate of alumina and water combined in substantially the proportions described, to convert the soluble silver salt contained in the prints into an insoluble salt.

In testimony whereof I have hereunto set my hand in presence of two subscribing witnesses.

THOMAS BAKER.

Witnesses:

EDWARD WATERS, WILLIAM GUEST HOLDEN.