Life of Bath
If the acid is renewed to the extent of the original amount after toning each 5000 feet, the bath is capable of toning 15,000 feet per 50 gallons of solution.
If even after revival, the tone remains flat, the bath is exhausted and should be thrown away.
After continued use, a slight bluish sludge will collect in the bath, but this is not harmful. Should this form, however, to any appreciable extent, it is due either to incorrect mixing, the action of light, or to contact with metallic surfaces.
Tone I
Tone I—Pale Blue (Iron)
The instructions are as for Tone H with the following modifications:
Positive Employed—Normal.
Time of Toning—Two to four minutes according to depth of tone desired.