LESSON 1
by placing the tray or
developing
tank in a sink, tray, or tank containing
cold water. If ice is
available,
it is usually satisfactory to put it in
the outside container.
Ice should
never be added directly to the processing
solution. As it melts,
it dilutes
the solution and changes its strength.
f. The temperature of all solutions (developer, rinse, fixing bath, and
wash) should be as near to each other as possible. If there is considerable
difference in temperature between the solutions, the emulsion is subjected
to excessive expansion and contraction which may cause it to wrinkle and/or
crack. This condition is known as reticulation.
6. Stop bath. When a negative is removed from the developing solution, the
emulsion is soft and small amounts of developer remain in the emulsion and
on its surface.
If the developer is not removed, it will continue its
reaction and cause stains.
To remove surplus developer, the negative is
placed in a rinse bath, generally referred to as the stop bath.
a. There are three general types of stop baths: water, acid, and acid-
hardening. Each has its specific purpose and should be used accordingly.
(1) Water stop bath. As a rinse, water helps to retard development
by diluting the developer. This reduces contamination of the fixing bath.
It is suitable for both negatives and prints, and sometimes precedes the
acid rinse in print processing to avoid the formation of gas bubbles that
may cause damage to the emulsion.
(2) Acid Stop Bath.
The acid stop bath contains acetic acid and
water.
An acid rinse is more effective than water, because it stops all
development by neutralizing the action of the developer.
This action
prolongs the life of the fixing bath.
(a) When working with photographic paper, use the recommended
acetic acid rinse bath. Use 1 1/2 ounces of 28 percent acetic acid to 32
ounces of water. Do not use this bath for negatives developed in a highly
alkaline solution such as Kodalith A & B because the violent reaction of the
alkali with the acid may cause pinholes in the emulsion.
(b) If an
acid
bath
is
not
available,
rinse
the
emulsion
thoroughly in water.
(3) Acid-hardening stop bath.
An acid-hardening rinse consists of
acetic acid, water, acid-pot, and chrome alum (the hardening agent). Use an
acid-hardening rinse bath to
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