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This is "Bromide Drag."
I attempted to come up with the words to explain this simply, but ended up going to two of the industry experts.
John Pytlak, Senior Technical Specialist for the Eastman Kodak Company for his aid. He explained it as follows:
Bromide drag can occur when processing film in a continuous processing machine. An area of high density uses up the developer. This stale developer clings to the film in a laminar layer, such that areas around the high-density objects may have insufficient development, which shows up as a streaks or a comet tale.
The interesting thing is that the laminar layer stays with the film during processing, keeping fresh developer from coming into contact with the film. It is this layer that must be broken up with fresh streams of developer via turbulation and agitation.
The name "bromide drag" comes from the bromide ion, which is byproduct of development.
And then from Paul Rutan of Triage Laboratories in Hollywood, one of the few labs (you can count them on the fingers of one hand) that can professionally and properly handle archival elements:
We actually call "bromide drag" the "directional effect", which it really is. Directional effect is caused by a rapid depletion of developer in heavily exposed areas.
This is basically what happens in laymen's terms.
It occurs when an area of heavy density passes through a poorly replenished or turbulated soup. The heavily exposed areas suck up the developer solution to develop those areas (such as heads and black hats) and, because the developer is suddenly weak, effectively under-exposes the area just past the heavy exposure, until the replenishment catches up. This causes a white (or black, depending on the element) streaking or halo effect. Normally B&W is processed from tails to head, causing the drag to go upwards.
Potassium Bromide is used most in a metal and hydroquinone developer. It is also created as a byproduct of normal development, and if a developer is reused for the need of longer processing times with subsequent processing. There is also an effect called bromide drag, which can happen when a developer has a high content of bromide- the negative will appear streaky after development. Bromide can also create a warm tone look and is used in warm tone paper developers for this.
Directional effect is caused by a rapid replenishment of developer in heavily exposed areas. Bromide drag is a general streaking effect caused by a build up of Bromide Sulfate in a soup that is poorly turbulated.
Bromide drag is a commonly used term for both defects.
Both can be remedied by proper replenishment and turbulation.
You'll see bromide drag on any number of older films. Now you know what you're seeing. Once the effect is part of the preservation element, there is very little that can be done to work around it.