Understanding Neutron Radiography Reading V-Kodak Part 2 of 3

The tank should be large enough to wash films as rapidly as they can be
passed through the other solutions. Any excess capacity is wasteful of water
or, with the same flow as in a smaller tank, diminishes the effectiveness with
which fixer is removed from the film emulsion. Insufficient capacity, on the
other hand, encourages insufficient washing, leading to later discoloration or
fading of the image. The "cascade method" of washing is the most
economical of water and results in better washing in the same length of time.
In this method, the washing compartment is divided into two sections. The
films are taken from the fixer solution and first placed in Section A. (See
Figure 75) After they have been partially washed, they are moved to Section
B, leaving Section A ready to receive more films from the fixer. Thus, films
heavily laden with fixer are washed in somewhat contaminated water, and
washing of the partially washed films is completed in fresh water.
Charlie Chong/ Fion Zhang
Radiography in Modern Industry. Rochester, NY: Eastman Kodak Co. 1980