This is a chlorinated hydrocarbon also known as methyl chloroform [in
the USA] and trichlor and currently banned by the Montreal Convention.
It is an excellent film cleaner which has most of the desirable
qualities. The main disadvantage is its reactions with zinc and
aluminium. These metals act as a catalyst to this substance's break down
and produce hydrochloric acid, dangerous to personnel and equipment.
Inhibitors have been found which work well as far as the metal
activation properties are concerned but they are not compatible with the
film base. The inhibited forms of this solvent (Chloroethene NU,
Genklene, Inhibisol) causes plasticiser to leech from the base at nearly
double the rate of uninhibited solvent and the base absorbs nearly three
times more inhibited solvent than uninhibited increasing the drying
times. Colour change may occur in the red layer of colour films using
inhibited solvent and the use of inhibited solvent probably reduces film
life.
It is arguable that because the film is only exposed to the solution for
a short period that the inhibitors will have little effect but it has
been shown that the inhibitors have a tendency to increase in
concentration in the tank. Inhibited solvent may not be compatible with
some of the bleaches used in colour processing. If insufficient washing
has resulted in some bleach [potassium ferricyanide] remaining in the
film, the inhibitors are thought to react with it forming light brown
spots or streaks during the cleaning process. This solvent can now only
be used for hand cleaning.