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dilute the solution in the tank to the required volume at 65 degrees (F).
Nature of Positive Film
Only good snappy positive film may be successfully tinted, since tinting tends to reduce contrast.
The depth of the tint obtained depends on the following factors :
1. Nature and Strength of the Dye-Bath
Except in special cases, such as fire scenes, sunset and moonlight effects, it is very undesirable to employ strong tints, since apart from the displeasing effect and irritation to the eye, the dyes produce a slight softening of the gelatine film when used at 80° (F) in a 1% solution.
Should it be necessary to employ concentrated baths in summer, either cool the dye bath or use a suitable hardener. This will be unnecessary if hardener is employed in the fixing bath after development, but otherwise if formalin (40%) be added to the dye-bath to the extent of 1 volume to 400 volumes of dye solution, no trouble will be encountered. During the winter months when it is advisable to treat all film after developing and fixing with glycerine, the latter may be incorporated with the dye bath, thereby eliminating an extra operation. The strength of the glycerine should be 2%, or two volumes per one hundred volumes of dye solution. In most cases, however, the addition of glycerine considerably retards the rate of dyeing and in order to obtain the same degree of tinting in a given time, the concentration of the dye bath should be increased accordingly.
When delicate tints are employed, the effect is both to remove the contrasting black and white effect, and to add a touch of warmth to the black deposit of silver, even in cases where the highlights are insufficiently stained to be noticeable. The result in many cases is equal to that obtained by partial toning.
2. Temperature of the Dye-Bath.
Although temperature has little effect on the rate of dyeing with the dyes recommended, when used without the addition of acid, it is advisable in all cases to work at 65 to 70° F. to produce uniform results and remove any danger of softening the film.
3. Time of Dyeing
In order to duplicate any particular tint with a given dye-bath the film may be dyed either by time or by inspection. Dyeing by time is reliable if the dye-bath does not contain acid, though if acid is present, in time the acidity decreases, causing a slowing down of the rate of dyeing, so that it becomes necessary to judge the progress of dyeing by inspection.
If two or more tints of the same color are required, it is better to vary the time of dyeing rather than to vary the dilution of the bath, as a means of reducing the number of individual dye-baths to
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