Reticulation is a tricky effect to achieve.
The emulsion reacts to extremes in temperature, shrinking and expanding, and can make a splotchy giraffe-pattern. Sometimes, when you try to do this on purpose, nothing happens, and when you don't want it, there it is. The examples here happened by accident, when I was washing film in tepid water, and someone flushed the toilet elsewhere in the house. The film was bathed in hot water and then cold, and the conditions were such that the emulsion crinkled up into the reticulated pattern. The pattern can be very uneven.