Most difficulties met with in toning may be traced to one or more of
the following causes:
_Uneven Toning_
This may be due to:
a. Grease on the film. Never project film before tinting or toning.
b. Drying spots on untoned film. If possible, always tint or tone
film immediately after washing and before drying.
c. Examination of the film too frequently during toning, causes an
oxidation of the toning solution in places where the solution fails
to drain from the film.
d. Insufficient or uneven washing of the film after bleaching and
before toning (Tones F and G).
_White Spots_
White spots are produced by particles of hypo or carbonate dust or
splashes of a solution of these, settling on the toned film. The
toned image consists of silver together with more or less silver
ferrocyanide and the ferrocyanides of uranium, iron and copper as the
case may be. Silver ferrocyanide is soluble in hypo while uranium and
iron ferrocyanides are soluble in a solution of sodium carbonate,
strong ammonia, etc., so that the white spots indicate those parts
where the toned image has been dissolved away.
Irregular white spots may also be formed if the film is imperfectly
squeegeed after washing and before drying, especially if the wash
water is slightly alkaline. When a spot of water on the toned film
evaporates, the small amount of alkali present in the water becomes
more concentrated and finally dissolves away more or less of the
tone, leaving a white spot on the film.
White spots due to these causes may be prevented by immersing the
film for a few seconds in a .5% solution of glacial acetic acid after
toning and before placing on the drying rack.
_Stained Highlights_
Are caused by:
a. Traces of fog on the film before toning.
b. An improperly compounded toning bath. All solutions when new
should be perfectly clear.
c. Premature exhaustion of the bath. This is due either to the action
of light or to the presence of some metal in the tank in the shape of
screw heads, faucets, pins, etc., which gather the tone and cause the
formation of sludge.
It is important to keep all solutions containing potassium
ferricyanide exposed as little as possible to daylight, to use only
wooden racks with wooden pegs, and to cover all metal parts very
carefully with acid resisting paint.
d. In dye-toning, stained highlights are due either to insufficient
washing after toning with copper, too strong a dye-bath, or an
incorrect amount of acid in the dye-bath.