salts; those prepared with organic salts become colourless when they approach neutrality, or when prepared with reducing salts.
6. Acid toning baths preserve their toning power indefinitely, and their activity is greater the less acid they are.
7. The tones obtained with the different papers and different baths depend upon the amount of gold deposited; the quicker the prints tone, and the more complete the toning action, the nearer the tone approaches to a blue black.
The colour obtained by toning varies with each bath, and in many cases with each different brand of paper, and the tone depends to a great extent, too, upon the negative. Some authorities even state that the tone of the print is fixed when the plate is developed, but the author cannot quite bear out this statement. Good bold negatives with plenty of contrast give more easily purple and black tones than weak muddy negatives devoid of any contrast, vigour, or sparkle. The following are the baths most commonly used at the present time, with some notes on the same : -
1. Acetate Bath.
Chloride of gold ............ 1 gr.
Acetate of soda ............ 30 grs.
Distilled water ......... ... 1002s.
Neutralise the gold with a pinch of common chalk mixed with I oz. of water, allow to settle, pour off the solution, and add to the acetate dissolved in the water. The bath must be kept at least twenty-four hours before use, and works better even when older. It gives brownish purple tones, which are very pleasing. The bath keeps fairly well if distilled water is used, and if no actinic light is allowed to gain access to it. If the bath be required for immediate use, hot water must be used, and the bath may be used as soon as cold. After toning, the bath should not be thrown away, but filtered and kept for use instead of water for diluting the next bath. The author prefers keeping a concentrated solution as follows : -
Chloride of gold ............ 15 grs.
Acetate of soda ...... ...... 480 ..
Distilled water, to make ......... ozs.
For use, mix J oz., equal to 1 gr. of gold, to | pint water for