used are different. The automatic developer consists of five chemicals: an activator,
reducers, a restrainer, a preservative, and a hardener.
a. Activator. The activator is the same chemical (potassium hydroxide) used in
manual developer solution and it serves the same purpose. It swells and softens the
emulsion so that the reducing agents can enter and act upon the silver bromide crystals.
It also provides the necessary alkaline medium for the solution.
b. Reducer. The reducer (phenidone and hydroquinone) reduces the exposed
silver bromide crystal to black metallic silver. ElonTM, used in manual developing, is
unpredictable above 75F and is replaced by phenidone in automatic processors.
Phenidone, which functions effectively at temperatures of 80 and 100F, builds up the
gray tones of the image. Hydroquinone, used in both manual and automatic solutions,
bring out the black tones, producing contrast.
c. Restrainer. The restrainer (potassium bromide) is also known as the starter
solution. The same chemical is used in both automatic and manual solutions. Its
function remains the same, to restrain the action of the reducers on unexposed silver
bromide crystals. It is not used in replenisher solutions for the reason explained above.
d. Preservative. The preservative is once again the same chemical with the
same function as in the annual developer. It prevents rapid oxidation of the chemicals
and prolongs their useful life.
e. Hardener. Gluteraldehyde, a hardening agent, is used in automatic system
but not in manual developer. Its function is to control the swelling of the emulsion,
thereby reducing film transportation problems and preventing emulsion damage during
f. Solvent. The chemicals in both kinds of developer solutions are all dissolved
in water. This is necessary both for the action of the chemicals and for the softening of
1-10. FIXER SOLUTION
Although the concentration of the fixer solution varies for the two methods of
processing, the chemicals used are basically the same. The fixer has four chemical
agents: an acidifier, a clearing agent, a hardener, and a preservative. All of the
chemicals are mixed with water, which serves as the solvent.
a. Acidifier. The acidifier (acetic acid) neutralizes any alkaline developer that
may be carried over from the developing solution and provides the required acidity for
the other chemicals to function. The acidifying action quickly stops development and
prevents formation of stains.