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Re Storing Faded Negatives and Prints

oz, water, sodium, washed, bath, gold, grs and solution

FADED NEGATIVES AND PRINTS, RE STORING Faded prints are more commonly met with than faded negatives, but whichever is treated,. success is more certain if the actual cause of fading is known (see " Fading, Causes of ").. When negatives fade the trouble is usually due either to insufficient fixing or to insufficient or improper washing after bleaching with mercury for the purpose of intensification. During the year inoo Sir William Crookes paid particular attention to the subject of restoring faded negatives—presumably those treated in the usual way and not intensified—and the follow ing process is advocated by him. The faded dry-plate negative is soaked for three hours in distilled water, and then immersed for from ten. to fifteen minutes (in the dark-room) in the following bath:— Water . . I oz. 50o ccs.

Pyro . . . 3 grs. 3 g.

Sodium metabisulphite 3 „ 3 ), Sodium carbonate . 36 „ 36 „ Sodium sulphite . 12 „ 12 „ The plate is next well washed, immersed in an ordinary " hypo " fixing bath for half an hour, and then washed in running water for from four to six hours. It is then toned with gold, for which purpose two solutions are required, one of ammonium sulphocyanide (io grs. to the ounce), and one of gold chloride (i gr. to the ounce) ; for use, 1 oz. of each is taken and 8 oz. of water added ; or, if desired, the com plete bath may be made up as— Water . . . 10 oz. r,000 ccs.

Am. sulphocyanide . ro grs. 2 g.

Gold chloride . I gr. .2 „ The plate is immersed in this bath for about ten minutes and finally washed for half an hour and dried. The fixing in " hypo " can be omitted if so wished, although it is desirable. The gold ton ing bath has the property of precipitating gold on the image and rendering it of a blacker colour.

Negatives that have been intensified with mercury may fade quickly, and to restore them they should be treated with a solution of potas sium sulphantimonate, commonly known as Schlippe's salt. The faded negative is first thoroughly soaked and then treated with zo grs. of Schlippe's salt dissolved in z oz. of water, until the desired result is obtained ; finally wash well.

The fading of prints has always been a trouble some matter. In the old days the necessity for thorough fixing and the complete removal of the " hypo " was not generally recognised, and the question of fading became so important that a committee was formed in May, 1855, to enquire into the causes, the Prince Consort con tributing L5o to the expenses of the inquiry. Since then, of course, many improved papers have taken the place of the old ones, and different causes have arisen. Platinum prints are said

never to fade, but nevertheless they sometimes appear to change their colour from the original pure black to a brownish or yellowish brown colour. According to Chapman Jones, such prints may be completely brought back to their original colour by unmounting and treating with a mixture of hydrochloric acid and chlorine water, made by adding a few drops of sodium hypochlorite solution to dilute hydrochloric acid (about one of acid to ten or more of water), until the odour of chlorine is distinctly notice able. Neither hydrochloric acid nor chlorine water alone is effective, though each does some thing towards the desired end. Several other methods have been advocated, but all are more troublesome, and not nearly so effective.

The restoration of silver (printed-out) prints is at all times a very risky performance. If they are old and yellow, and of value, they should be copied—preferably through light blue glass— before any attempt is made to tamper with them, because of the risk of spoiling the originals. One process is to bleach the yellowed albumen print in a mercuric chloride solution as used for intensifying, well wash, and then to develop in an old hydroquinone or metal developer (without bromide), or preferably to immerse in a 5 per cent. solution of sodium sulphite, and finally wash well. This process is not reliable. An elaborate process of restoring silver prints, and one for which the inventor (H. Jandaurek) was awarded a silver medal in 1888, is as follows. Two solutions are required : A. Distilled water . 35 oz. f,000 ccs.

Sodium tungstate 6o8 grs. 5 g.

B. Distilled water i oz. 40o ccs.

Calcium carbonate (pure) 5 grs. 4 g.

Chloride of lime . I '2 „ r ), Gold and sodium. chloride 5 „ 4 The B solution should be kept in a yellow bottle or in the dark for twenty-four hours. The faded prints are unmounted, well washed, and placed in 8 oz. of the A solution to which oz. to oz. of B has been added. They should remain in this toning bath until they good purple tone, and they are then well washed and fixed with " hypo " (i oz. to to oz. of water) until all the yellowness has disappeared, which may take one hour or more ; finally, they are washed well.

As stated above, all print restoration processes are more or less unreliable, and need to be used with great caution. Any details that have vanished from the faded print cannot be brought back, and all that the restoration process does is to strengthen the weak parts of the print, and as much as this can be done equally well by making a copy in a proper manner.