Tone B
Tone B Red (Uranium)
Positive Employed—Thin.
Immerse the well washed film in the following:
| Avoirdupois | Metric | ||
| Uranium Nitrate (Neutral) | 16½ ozs. | 500 | grams |
| Potassium Oxalate (Neutral) | 16½ ozs. | 500 | grams |
| Potassium Ferricyanide | 6½ ozs. | 200 | grams |
| Ammonium Alum | 2½ lbs. | 1200 | grams |
| Hydrochloric Acid 10% | 1 quart | 1000 | cc. |
| Water to | 50 gals. | 200 | liters |
Mix in the order given. The solution obtained should be perfectly clear and pale yellow in color.
In view of the fact that the nature of the tone is influenced largely by the acid content, it is very important that the uranium nitrate should contain no free acid, and this may be assured by neutralizing a solution with dilute ammonia until a slight permanent precipitate is obtained.
It is convenient to keep stock solutions of the above (say, 10% solutions) from which a new bath may be expeditiously compounded. A 10% hydrochloric acid solution is one containing 10 parts by volume of the concentrated acid per 100 volumes of the final solution.
Temperature of Toning—65 degrees to 70 degrees F.
Time of Toning—Ten minutes.
Since this and the following single solution methods of toning produce a marked intensification of the silver image—which intensification increases with the time of toning—it follows that the nature of the tone changes with time also.
The composition of the bath has been so adjusted that the maximum effect is produced in about 10 minutes, the tone passing through a series of changes from brown to red during this time.
It is therefore possible to obtain intermediate tones by withdrawing the film from the bath at shorter intervals, though in such cases the contrast of the original black and white film should be adjusted accordingly, since with slight toning very little intensification takes place. (See tones C and D.)
Time of Washing—Ten to fifteen minutes.
The highlights will become clear in the above time, though a thin yellowish brown veil may remain in the clear gelatine as a result of the intensification of minute traces of fog, but this has no effect on projection. If the bath is working correctly the yellowish veil is only just perceptible, but if appreciably visible, then either the film was fogged during development, or the bath was not compounded correctly. Washing should not be carried out for too long a period, especially with water inclined to be alkaline, because the toned image is soluble in alkali.
Life of Bath
Fifty gallons of solution will tone about 5000 feet of film without any appreciable change in the tone, after which the rich tone tends to flatness as a result of a deficiency of acid in the bath. At this point the bath may be revived by the further addition of acid to the extent of the original amount, when a further 5000 feet may be toned. At this stage the richness of tone falls off rapidly and the bath should be thrown away.
Used intermittently over a period of several days the life of the bath is approximately the same.
With continued use a slight brownish flocculent precipitate may form in the bath, but this should only be slight, otherwise it is caused by incorrect mixing, the action of light, or by contact with a metallic surface.